Patent Publication Number: US-2006002273-A1

Title: Recording/reproducing head, method of producing the same, recording apparatus and reproducing apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a recording/reproducing head for recording and reproducing polarization information recorded on a dielectric substance, such as a ferroelectric recording medium, as well as a method of producing the recording/reproducing head, and a recording apparatus and a reproducing apparatus which use the recording/reproducing head.  
      2. Description of the Related Art  
      A technique of a recording/reproducing apparatus which uses SNDM (Scanning Nonlinear Dielectric Microscopy) for nano-scale analysis of a dielectric recording medium is suggested by the inventors of the present invention. In SNDM, it is possible to increase its resolution associated with the measurement to sub nanometer resolution, by using an electric conductive cantilever (or probe) with a small probe mounted on its tip, which is used for AFM (Atomic Force Microscopy) or the like. Recently, the development of a super high density recording/reproducing apparatus has been advanced, wherein the apparatus records data onto a recording medium having a recording layer made of a ferroelectric material, by using the technique of SNDM (refer to Japanese Patent Application Laying Open NO. 2003-085969).  
      The recording/reproducing apparatus of this type which uses SNDM reproduces information by detecting a positive or negative direction of polarization of the recording medium. This is performed by using a change in an oscillation frequency of a LC oscillator, which includes (i) a high frequency feedback amplifier including an L component, (ii) a conductive probe mounted on this amplifier, and a capacitance Cs of the ferroelectric material under the probe, caused by a change ΔC in a small capacitance due to a non-linear dielectric constant which have origin in the distribution of the positive and negative of the polarization. Namely, it is performed by detecting the change in the distribution of the positive and negative of the polarization, as a change Δf in the oscillation frequency.  
      Moreover, by applying an alternating electric field whose frequency is sufficiently low with respect to the oscillation frequency in order to detect a difference in the positive and negative of the polarization, the oscillation frequency is changed along with the alternating electric field, and the rate of change in the oscillation frequency including its sign is determined by the non-linear dielectric constant of the ferroelectric material under the probe. Then, by FM (Frequency Modulation)-demodulating and extracting a component due to the alternating electric field, from a high-frequency signal of the LC oscillator which is FM-modulated in accordance with the change in the small capacitance A C along with the application of the alternating electric field, the record information (data) recorded on the ferroelectric recording medium is reproduced.  
     SUMMARY OF THE INVENTION  
      The record and reproduction of the record information is performed by using the probe as a recording/reproducing head. Since the probe constitutes a part of a resonance circuit, its resistance value (its electric resistance value) is desired to be relatively small. From the study of the inventers of the present invention, it is found out that the resistance value of the probe can be reduced by depositing an alloy thin film, including platinum, onto silicon.  
      On the other hand, it is required that the probe has abrasion resistance, in view of abrasion and deformation caused by contact with the recording medium or the like. Considering from such a viewpoint, the probe provided with the alloy thin film, including platinum, is easily abraded, and the tip of the probe wears away with a continued use, so that there is such a technical problem that it is difficult or substantially impossible to continue its use as the probe. Moreover, if a thin film of platinum exfoliates or comes off, it no longer satisfies a request as the probe whose resistance value is relatively small. Even from this point, there is such a technical problem that it is difficult or substantially impossible to continue the use as the probe.  
      It is therefore an object of the present invention to provide a recording/reproducing head which is highly resistant to deterioration, such as abrasion, and whose electric resistance value is relatively small, as well as a method of producing the recording/reproducing head, and a recording apparatus and a reproducing apparatus which use the recording/reproducing head.  
      The above object of the present invention can be achieved by a recording/reproducing head for performing at least one of a record operation of recording information onto a dielectric recording medium and a reproduction operation of reproducing the information from the dielectric recording medium, the recording/reproducing head provided with: a support member which extends in a longitudinal direction (for example a longitudinal direction of the recording/reproducing head); a projection portion which is mounted on the support member such that a tip of the projection portion faces the dielectric recording medium; and a conductive layer which covers a part portion other than at least the tip out of the projection portion, the projection portion containing a harder material than that of the conductive layer.  
      According to the recording/reproducing head of the present invention, by covering the surface of the projection portion with the conductive layer, it is possible to reduce the electric resistance value of the recording/reproducing head, and it is also possible to realize the recording/reproducing head which is resistant to the deterioration, such as abrasion.  
      Specifically, the recording/reproducing head of the present invention is provided with the support member which extends in the longitudinal direction. The support member may or may not have electric conductivity. Therefore, although there are various types of materials which can be used as the support member, it is preferable to select an appropriate material in accordance with a resonance frequency of a resonance circuit (in other words, an oscillation frequency of an oscillator) in a reproducing apparatus, as described later. Alternatively, by selecting an appropriate material, it is also possible to change a vibration frequency obtained when the recording/reproducing head is moved along the surface of the information recording medium, as occasion demands. The projection portion is mounted on one end of the support member such that the tip of the projection portion faces the dielectric recording medium. The projection portion may be mounted upright on the support member. The material used for the projection portion is harder than the material used for the conductive layer. As the projection portion, for example, diamond, boron nitride, and the like are used, as described later.  
      Then, the surface of the projection portion is covered with the conductive layer. In particular, the part other than at least the tip of the projection portion is covered with the conductive layer. In other words, the tip of the projection portion is not covered with the conductive layer, and the surface thereof is exposed. At this time, the tip is preferably large enough to contact or substantially contact the dielectric recording medium (i.e. as large as the diameter of the tip portion, the exposed portion, or the like). Moreover, it is enough if the path of an electric field is formed in the conductive layer and if the conductive layer covers the projection portion to an extent to show a function as the recording/reproducing head in a recording apparatus or a reproducing apparatus as described later. Incidentally, the conductive layer is preferably provided with a metal material having electric conductivity, and a material containing platinum or the like is used, as described later. In particular, the conductive layer preferably has larger electric conductivity than those of the projection portion and the support member.  
      If the recording/reproducing head of the present invention is used in the recording apparatus or the reproducing apparatus and if an electric field is supplied to the recording/reproducing head, the electric field is applied to between the dielectric recording medium and the recording/reproducing head of the present invention, mainly via the conductive layer (i.e. the path of the electric field formed in the conductive layer). Namely, since the conductive layer is formed, it is possible to reduce the electric resistance value of the recording/reproducing head as a whole. Moreover, the tip of the projection portion is not covered with the conductive layer but exposed. However, the exposed portion is really small from the view of the entire recording/reproducing head, and the path of the electric field formed in the projection portion is extremely short. Therefore, it does not greatly influence on the change of the electric resistance value of the recording/reproducing head as a whole, and as a result, it is possible to suppress the electric resistance value of the recording/reproducing head, to thereby realize the recording/reproducing head having a small electric resistance value.  
      In addition, because the tip of the projection portion is exposed, it is the tip that can actually contact the dielectric recording medium. The projection portion, including the tip, is resistant to the deterioration, such as abrasion, grinding, and polishing, because the projection portion uses a harder material than the conductive layer. More preferably, a material harder than the material used for the dielectric recording medium is used for the projection portion. Therefore, even if the surface (or at least a part of the surface) of the projection portion is covered with the conductive layer which is a relatively soft material, by using a harder material on the tip which can actually contact the dielectric recording material, it is possible to provide strong deterioration resistance.  
      Consequently, according to the recording/reproducing head of the present invention, it has resistant to the deterioration, such as abrasion, and it is possible to reduce its resistance value. Thus, it is possible to extend its lifetime of use, by inhibiting the deterioration of the recording/reproducing head. Moreover, by reducing the electric resistance value, it is possible to inhibit the attenuation of a signal in the resonance circuit, in the reproducing apparatus described later.  
      Incidentally, it is preferable that the projection portion also has electric conductivity, as described later. However, from the viewpoint that an electric field can be applied via the conductive layer, the projection portion is not necessarily provided with the electric conductivity.  
      Moreover, the support member and the projection portion may be formed in one body. Namely, even if the support member and the projection portion are formed from a single member, if the support member and the projection portion can be distinguished from a difference in their shapes, then, this aspect is included in the present invention.  
      In one aspect of the recording/reproducing head of the present invention, the conductive layer at least partially covers a surface of the support member on a side where the projection portion is mounted, in addition to the part other than at least the tip out of the projection portion.  
      According to this aspect, by at least partially covering the support member, it is possible to further reduce the electric resistance of the recording/reproducing head as a whole. Incidentally, the support member in this case may not necessarily have electric conductivity.  
      In another aspect of the recording/reproducing head of the present invention, the tip has such a shape that the tip protrudes from an edge of the conductive layer which surrounds the tip.  
      According to this aspect, the projection portion (i.e. the tip thereof) is not only exposed but also protrudes from the conductive film, so that it is possible to reduce the possibility that the conductive layer contacts the dielectric recording medium, and it is possible to provide the stronger deterioration resistance of the recording/reproducing head.  
      Incidentally, it is preferable that the tip protrudes to an extent enough to contact or substantially contact the dielectric recording medium. Alternatively, it is preferable that the tip protrudes to an extent enough to prevent the conductive layer from contacting the dielectric recording medium.  
      In another aspect of the recording/reproducing head of the present invention, the tip has a rounded shape.  
      According to this aspect, it is possible to contact the recording/reproducing head with the dielectric recording medium with stability, in the record operation of the recording apparatus and in the reproduction operation of the reproducing apparatus, as described later. Namely, since the tip of the recording/reproducing head has a rounded shape, it easily contacts the dielectric recording medium at a point.  
      In another aspect of the recording/reproducing head of the present invention, the tip has a flat surface, located on a same surface as an edge of the conductive layer which surrounds the tip.  
      According to this aspect, the tip (e.g. the surface of the tip which could actually contact the dielectric recording medium) is flattened to locate on the same surface as the conductive layer. Here, “be located on the same surface” in the present invention indicates such construction that the tip (e.g. the surface of the tip which could actually contact the dielectric recording medium) and the edge of the conductive layer, which surrounds the tip, can contact the dielectric recording medium at the same time, or can be regarded to contact it substantially at the same time. The “same surface” in the present invention literally indicates the same surface, and also broadly includes even such a positional relationship that can be regarded as the same surface. Therefore, it is possible to make the tip of the projection portion and the edge portion of the conductive film approach the dielectric recording medium, to thereby improve the resolution of the head. Namely, it is possible to reduce the size (dimension) of an information unit which can be recorded and reproduced.  
      In another aspect of the recording/reproducing head of the present invention, the projection portion has electric conductivity.  
      According to this aspect, by providing the projection portion with electric conductivity, it is possible to further suppress the electric resistance value of the recording/reproducing head as a whole.  
      In an aspect of the recording/reproducing head provided with the projection portion which has electric conductivity, as described above, the projection portion may contain diamond to which impurities are doped.  
      By constituting in this manner, diamond (i.e. diamond to which impurities are doped), which is superhard and excellent in lubricating ability, can be used as the projection portion. Because of its superhard, it is possible to increase the abrasion resistance of the conductive layer much more. And because of its electric conductivity caused by the doped impurities, it is possible to suppress the electric resistance value of the recoding/reproducing head. Incidentally, in this aspect, the impurities which are doped may be boron, for example. Alternatively, even in the case of impurities associated with other atoms (other material), any impurities which can cause electric conductivity to diamond will suffice.  
      In an aspect of the recording/reproducing head provided with the projection portion which has electric conductivity, the projection portion may contain boron as the impurities.  
      By constituting in this manner, it is possible to receive various benefits owned by the recording/reproducing head of the present invention, by using boron nitride, for example.  
      In another aspect of the recording/reproducing head of the present invention, the conductive layer contains platinum.  
      According to this aspect, by using platinum, which is a relatively hard material, it is possible to increase the abrasion resistance of the conductive layer. In addition, by virtue of platinum which has electric conductivity, it is possible to suppress the electric resistance value of the conductive film. Incidentally, it is more preferable to use alloy, such as platinum palladium and platinum iridium, as the conductive layer.  
      In another aspect of the recording/reproducing head of the present invention, the projection portion contains a non-conductive material.  
      According to this aspect, even if the projection portion does not have electric conductivity (i.e. non-conductive), it is possible to apply an electric filed to between the projection portion and the dielectric recording medium via the conductive film.  
      In another aspect of the recording/reproducing head of the present invention, the conductive layer is formed on a foundation layer which is more adhesive than said conductive layer.  
      According to this aspect, it is possible to further prevent the conductive layer from exfoliating or peeling off or cut off, and it is possible to extend the lifetime of use of the recording/reproducing head. As the foundation layer, for example, a metal thin film, such as titanium, may be used.  
      The above object of the present invention can be also achieved by a production method of producing the above-described recording/reproducing head (including its various aspects), the production method provided with: a first forming process of forming the support member and the projection portion; a second forming process of forming the conductive layer to cover at least the projection portion; and an exposing process of expositing at least the tip.  
      According to the production method of the present invention, it is possible to produce the above-described recording/reproducing head relatively easily.  
      Specifically, at first, in the first forming process, the projection portion and the support member are formed. They can be formed by combining various processes, such as patterning by a resist, etching, and a film formation method (or a film growth method).  
      Then, in the second forming process, the conductive layer is formed to cover the projection portion. The conductive layer may be formed to cover the support member in addition to the projection portion. The conductive layer (i.e. a conductive film) can be formed by using a vacuum evaporation method, for example. Alternatively, the conductive layer may be formed by using other film formation methods (e.g. spattering, Chemical Vapor Deposition (CVD), or the like)  
      Then, after or at the same time of the second forming process, in the exposing process, the tip of the projection portion is exposed from the conductive layer. In the exposing process, various methods as described later can be used, and in any method adopted, it is possible to expose the tip appropriately.  
      Consequently, according to the production method of the present invention, it is possible to produce the above-described recording/reproducing head efficiently and relatively easily.  
      In one aspect of the production method of the present invention, in the second forming process, after a foundation layer which is more adhesive than the conductive layer is formed, the conductive layer is formed on the foundation layer.  
      According to this aspect, it is possible to produce the recording/reproducing head in which the conductive layer is further prevented from exfoliating or peeling off or cut off. Therefore, it is possible to produce the recording/reproducing head whose lifetime of use is long.  
      In another aspect of the production method of the present invention, in the exposing process, the tip is exposed by grinding or polishing the conductive layer formed on the tip.  
      According to this aspect, if the conductive layer is grinded or polished, the tip of the projection portion can be exposed relatively easily. Therefore, without influenced by complicated production parameters and a production environment or the like, it is possible to produce the recording/reproducing head of the present invention relatively easily.  
      In another aspect of the production method of the present invention, the second forming process further includes a resist coating process of coating a resist onto at least the tip before the conductive layer is formed, and in the exposing process, the tip is exposed by removing the resist.  
      According to this aspect, by using the patterning of the resist, it is possible to expose the tip selectively. Moreover, by changing the shape of the patterning (i.e. the shape of the coated resist), it is also possible to adjust the size and shape or the like of the tip which is exposed.  
      In another aspect of the production method of the present invention, in the exposing process, the tip is exposed by applying a pulse voltage to a part which covers at least the tip out of the conductive layer to exfoliate the conductive layer which covers the tip.  
      According to this aspect, the conductive layer is exfoliated by using the principle of spattering, so that it is possible to expose the tip relatively easily.  
      In another aspect of the production method of the present invention, in the first forming process, a silicon ( 100 ) substrate is used as a cast, and the first forming process is provided with: a mold-forming process of forming a mold of the projection portion by performing anisotropic etching with respect to the cast; and a projection-portion-forming process of forming the projection portion by using the mold of the projection portion.  
      The silicon substrate has such a property that an etching rate varies depending on a difference of interatomic bonds in a crystal lattice surfaces of a ( 100 ) surface and a ( 111 ) surface thereof. Therefore, according to this aspect, it is possible to form the mold in the projective shape (or in a pyramid-shape), which is required for the formation of the projection portion, by performing the anisotropic etching using such a property, in the mold-forming process. Then, the use of the mold allows the formation of the projection portion, relatively easily, in the projection-portion-forming process.  
      Incidentally, not only the silicon substrate but also a material having the above-described property can be used as the cast in place of the silicon substrate.  
      The above object of the present invention can be also achieved by a recording apparatus for recording data onto a dielectric recording medium, the recording apparatus provided with: the above-described recording/reproducing head (including its various aspects); and a record signal generating device for generating a record signal corresponding to the data.  
      According to the recording apparatus of the present invention, it is possible to record the data on the basis of the record signal generated by the recording signal generating device, while taking advantage of the above-described recording/reproducing head of the present invention. Namely, in the record operation, even if the recording/reproducing head contacts the dielectric recording medium, there is little possibility of damage or the like, because the tip of the projection portion is exposed to thereby have the strong deterioration resistance.  
      Therefore, it is possible to record the data with more stability and extend the lifetime of the recording apparatus.  
      The above object of the present invention can be also achieved by a reproducing apparatus for reproducing data recorded on a dielectric recording medium, the reproducing apparatus provided with: the above-described recording/reproducing head (including its various aspects); an electric field applying device for applying an electric field to the dielectric recording medium; an oscillating device whose oscillation frequency varies depending on a difference in a capacitance corresponding to a non-linear dielectric constant of the dielectric recording medium; and a reproducing device for demodulating and reproducing an oscillation signal from the oscillating device.  
      According to the reproducing apparatus of the present invention, by applying an electric field to the dielectric recording medium by using the electric filed applying device, the oscillation frequency of the oscillating device is changed, due to a change in the capacitance corresponding to a change in the non-linear dielectric constant of the dielectric recording medium. Then, the oscillation signal corresponding to the change in the oscillation frequency of the oscillating device is demodulated and reproduced by the reproducing device, to thereby reproduce the data.  
      Particularly in the present invention, the data can be reproduced by taking advantage of the above-described recording/reproducing head of the present invention. Namely, in the reproduction operation, even if the recording/reproducing head contacts the dielectric recording medium, there is little possibility of damage or the like, because the tip of the projection portion is exposed to thereby have the strong deterioration resistance. Moreover, since the resistance value of the recording/reproducing head is small, it is possible to avoid the disadvantage of the attenuation of the oscillation signal from the oscillating device.  
      Therefore, it is possible to reproduce the data with more stability and extend the lifetime of the reproducing apparatus.  
      The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with reference to preferred embodiment of the invention when read in conjunction with the accompanying drawings briefly described below.  
      As explained above, according to the recording/reproducing head of the present invention, it is provided with: the support member; the projection portion; and the conductive layer. Therefore, it is possible to realize the recording/reproducing head which is resistant to the deterioration, such as abrasion, and whose electric resistance value is relatively small.  
      Moreover, according to the production method of the present invention, it is provided with: the first forming process; the second forming process; and the exposing process. Therefore, it is possible to produce the recording/reproducing head of the present relatively easily and efficiently.  
      Moreover, according to the recording apparatus of the present invention, it is provided with the recording/reproducing head of the present invention and the record signal generating device. Therefore, it is possible to receive various benefits owned by the recording/reproducing head of the present invention, and thus, it is possible to record the data with more stability and extend the lifetime of the recording apparatus.  
      Furthermore, according to the reproducing apparatus of the present invention, it is provided with: the recording/reproducing of the present invention head; the electric field applying device; the oscillating device; and the reproducing device. Therefore, it is possible to receive various benefits owned by the recording/reproducing head of the present invention, and thus, it is possible to reproduce the data with more stability and extend the lifetime of the reproducing apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A ,  FIG. 1B , and  FIG. 1C  are a cross sectional view, a plan view, and a side view, respectively, conceptually showing one specific example of a recording/reproducing head in an embodiment of the present invention;  
       FIG. 2A ,  FIG. 2B , and  FIG. 2C  are a cross sectional view, a plan view, and a side view, respectively, conceptually showing another specific example of the recording/reproducing head in the embodiment of the present invention;  
       FIG. 3  is a cross sectional view conceptually showing one process of a production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 4  is a cross sectional view conceptually showing another process of a production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 5A  and  FIG. 5B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 6A  and  FIG. 6B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 7A  and  FIG. 7B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 8A  and  FIG. 8B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 9A  and  FIG. 9B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 10  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 11  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 12  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 13  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 14  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 15A  and  FIG. 15B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 16A  and  FIG. 16B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 17  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 18  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 19A ,  FIG. 19B , and  FIG. 19C  are cross sectional views conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 20A ,  FIG. 20B , and  FIG. 20C  are cross sectional views conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 21  is a block diagram conceptually showing a basic structure of a dielectric recording/reproducing apparatus in an embodiment which adopts the recording/reproducing head in the embodiment of the present invention;  
       FIG. 22A  and  FIG. 22B  are a plan view and a cross sectional view, respectively, conceptually showing a dielectric recording medium used for information reproduction on the dielectric recording/reproducing apparatus in the embodiment;  
       FIG. 23  is a cross sectional view conceptually showing a record operation of the dielectric recording/reproducing apparatus in the embodiment; and  
       FIG. 24  is a cross sectional view conceptually showing a reproduction operation of the dielectric recording/reproducing apparatus in the embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The embodiment associated with the recording/reproducing head of the present invention will be hereinafter explained with reference to the drawings.  
     (1) Embodiment of Recording/Reproducing Head  
      At first, with reference to  FIG. 1  to  FIG. 20 , the embodiment associated with the recording/reproducing head of the present invention will be explained.  
      (i) Structure of Recording/Reproducing Head  
      At first, with reference to  FIG. 1  to  FIG. 2 , the structure (i.e. basic structure) of the recording/reproducing head in the embodiment will be explained.  FIG. 1A ,  FIG. 1B , and  FIG. 1C  conceptually show one example of the structure of the recording/reproducing head in the embodiment.  FIG. 2A ,  FIG. 2B , and  FIG. 2C  conceptually show another specific example of the structure of the recording/reproducing head in the embodiment.  
      As shown in  FIG. 1A , a recording/reproducing head  100  in the embodiment is provided with: a diamond tip  110 , which is one specific example of the “projection portion” of the present invention; a conductive film  120 ; and a support member  130 .  
      The diamond tip  110  has a narrowed and pointed tip so that an electric field is applied to a dielectric recoding medium  20  as described later (refer to  FIG. 22 ) from the tip side, in the record/reproduction operations of the recording/reproducing head  100 . In particular, the diamond tip  110  preferably has electric conductivity, obtained by doping boron or the like to diamond at the time of production.  
      Incidentally, in place of the diamond tip  110 , for example, boron nitride can be used. Alternatively, what is harder than the conductive film  120  and has electric conductivity can be used in place of the diamond tip  110 .  
      The conductive film  120  is formed to cover the surfaces of the diamond tip  110  and the support member  130 . In particular, as shown in  FIG. 1A , the conductive film  120  is formed except on the tip of the diamond tip  110 .  
      As the conductive film  120 , for example, alloy, such as platinum palladium and platinum iridium, can be used. Considering that the conductive film  120  could also contact the dielectric recording medium  20  as with the diamond tip  110 , the conductive film  120  is preferably a hard film. However, the conductive film  120  does not require hardness like the diamond tip  110 , and may require hardness to an extent enough to maintain a constant form.  
      The support member  130  is a base for supporting the recording/reproducing head  100 . The support member  130  may or may not have electric conductivity. Moreover, as described later, the support member  130  and the diamond tip  110  may be formed in one body (refer to  FIG. 3  etc.).  
      Furthermore, as described later, the support member  130  constitutes a part of a resonance circuit  14  in the reproduction operation as apart of a probe  11  (refer to  FIG. 21 ). Thus, it is possible to select the material in accordance with the inductance of the support member  130  so as to obtain a desired resonance frequency (oscillation frequency). Moreover, by selecting the material in this manner, it is also possible to change the vibration frequency of the probe  11 , as occasion demands.  
       FIG. 1B  is a plan view when the recording/reproducing head  100  shown in  FIG. 1A  is observed from the bottom side (i.e. the side covered with the conductive film  120 ). The tip portion of the diamond tip  110  is exposed from the conductive film  120 . Incidentally, in  FIG. 1B , the conductive film  120  does not cover the entire surface of the support member  130  (more specifically, a portion corresponding to a support base  130   a ), but it is enough if the conductive film  120  can be electrically connected to an alternating current (AC) signal generator  21  and a record signal generator  22  in a dielectric recording/reproducing apparatus  1 , as described later.  
      Incidentally, the tip radius of the tip portion of the diamond tip  110  which protrudes from the conductive film  120  is approximately from 10 to 50 nm. However, even in the case of more than or less than the above-described diameter, it is possible to receive the same benefits. This tip radius is a significant factor to determine the radius of the polarization formed correspondingly to the record data recorded onto the dielectric recording medium  20  (refer to  FIG. 22 ) as described later. Thus, it is preferably extremely small, on the order of 10 nm.  
      The support member  130  is unified with the support base  130   a . Specifically, the support base  130   a  is fixed, and the support member  130  is unified with the support base  130   a  such that the support member  130  can move (or wobble or oscillate) slightly as a cantilever in accordance with its elasticity. Even in this case, the support member  130  and the support base  130   a  may be collectively referred to as the support member  130 .  
      Now, as the recording/reproducing head of the conventional dielectric recording/reproducing apparatus, such a recording/reproducing head that alloy which has electric conductivity, such as platinum iridium, is deposited on a silicon substrate is used. However, such a recording/reproducing head has the problem that the lifetime of use is short because the tip is abraded or grinded in contacting the dielectric recording medium.  
      According to the recording/reproducing head in the embodiment, a hard member, such as the diamond tip  110 , protrudes from one end of the conductive film  120 , so that it is possible to prevent deterioration caused by the abrasion and grinding in contacting the dielectric recording medium. Namely, the diamond tip  110  is used as a main factor to prevent the abrasion of the conductive film  120  or the like. By this, it is possible to realize the recording/reproducing head which is highly resistant to the deterioration, such as abrasion and grinding. Consequently, it is possible to extend the lifetime of use of the recording/reproducing head.  
      Moreover, the mere use of the diamond tip  110  is not enough and there will remain difficulty in the use as the recoding/reproducing head because of the magnitude of the electric resistance of the diamond tip  110 . Thus, by using diamond having electric conductivity as the diamond tip  110 , and coating the conductive film  120  on its surface, it is possible to reduce the electric resistance with respect to an electric field which is applied to between the recording/reproducing head  100  and the dielectric recording medium  20 . This is because a path (i.e. electricity passage) of the electric field (or an electric current) flown in the diamond tip  110  can be shorten. Namely, the electric field is applied to between the recording/reproducing head  100  and the dielectric recording medium  20  via a very short path corresponding to the tip of the diamond tip  110  and a path in the conductive film  120 . This gives such a significant advantage that it is possible to inhibit the attenuation of a signal which is read or recorded by the recording/reproducing head  100 , as described later.  
      Incidentally, as shown in  FIG. 1C , the tip of the diamond tip  110  may be rounded. With respect to the extent of the rounded shape, it may be sphere or may have a shape with a constant radius. Alternatively, a shape without angular portions will suffice. By this, it is possible to stabilize the contact with the dielectric recording medium  20  in the record and reproduction operations. Moreover, it is possible to reduce useless discharge (i.e. useless application of the electric field) between the diamond tip  110  and the dielectric recording medium  20 , to thereby reduce electricity consumption and improve the efficiency of the record and reproduction operations.  
      Moreover, the tip of the diamond tip  110  does not necessarily protrude from the conductive film  120 , and as show in  FIG. 2A , it may be constructed such that the tip (the tip surface) of the diamond tip  110  and the edge portion of the conductive film  120 , which surrounds the tip, are located on the same surface or substantially the same surface. Even in such a construction, it is possible to receive the same benefits as those of the recording/reproducing head  100  shown in  FIG. 1A  to  FIG. 1C .  
       FIG. 2B  is a schematic diagram of a recording/reproducing head  102  shown in  FIG. 2A , viewed from the bottom side. As shown in  FIG. 2B , the tip (the tip surface) of the diamond tip  110  is located on substantially the same surface as the edge portion of the conductive film  120  which surrounds the tip. Thus, the tip (the tip surface) of the diamond tip  110  is preferably flat, as opposed to the recording/reproducing head  100  shown in  FIG. 1A  to  FIG. 1C . Even in this case, however, it is possible to make the tip of the diamond tip  110  rounded, as in a recording/reproducing head  101  as shown in  FIG. 1C .  
      Moreover, even if the diamond tip  110  is not formed at one end portion of the support member  130 , as shown in  FIG. 2C , the diamond tip  110  may be formed at a predetermined position of the support member  130 , for example.  
      (ii) Production Method for Recording/Reproducing Head  
      Next, with reference to  FIG. 3  to  FIG. 20 , the production method for the recording/reproducing head in the embodiment will be explained.  FIG. 3  to  FIG. 20  conceptually show each process of the production method for the recording/reproducing head in the embodiment.  
      Incidentally, the recording/reproducing head produced in the production method which will be explained here is such that the diamond tip  110  and the support member  130  are unified. However, even if the diamond tip  110  and the support member  130  are not unified, the recording/reproducing head can be produced in the same production method, and it is obvious that such a production method is also included in the scope of the present invention.  
      At first, as shown in  FIG. 3 , a silicon substrate  201  is prepared. The silicon substrate  201  mainly becomes a mold for the recording/reproducing head. Incidentally, it is preferable to prepare such a silicon substrate  201  that a silicon dioxide film is formed along (or in parallel with) its ( 100 ) surface in a crystal lattice structure in a later process. This is, as described later, to form the projective (or pyramid-like) shape of the diamond tip  110  by performing anisotropic etching. The silicon substrate  201  is referred to as a ( 100 ) substrate.  
      Then, as shown in  FIG. 4 , silicon dioxide (SiO 2 ) films  202  are formed with respect to a front surface (or an upper surface in  FIG. 4 ) and back surface (or a downside surface in  FIG. 4 ) of the silicon substrate  201 . In this case, the silicon dioxide films  202  may be formed on the surfaces by providing the silicon substrate  201  under an oxidizing atmosphere at high temperature.  
      Then, as shown in  FIG. 5A , a photoresist  203  is coated by spin coating method, for example, and patterning is performed. Specifically, after the photoresist  203  is coated onto the silicon dioxide film  202  formed on one of the surfaces of the silicon substrate  201 , ultraviolet rays or the like are irradiated thereon with a photo mask in which a portion corresponding to the diamond tip  110  is patterned. Then, by developing it, the patterning of the photoresist  203  is performed as shown in  FIG. 5A .  
      Incidentally,  FIG. 5B  shows the silicon substrate  201  etc. in  FIG. 5A  viewed from the top side (i.e. from the side where the photoresist  203  is patterned). As shown in  FIG. 5B , in the portion where the diamond tip  110  of the recording/reproducing head  100  will be formed later, a window (or space portion) at which the photoresist  203  is not coated can be seen. The diamond tip  110  will be formed later in accordance with the shape of this window.  
      Then, as shown in  FIG. 6A , etching is performed with respect to the silicon substrate  201  in which the photoresist  203  is patterned as shown in  FIG. 5 . Here, for example, BHF (Buffered HydroFluoric acid) or the like is used to perform the etching with respect to the portion where the photoresist  203  is not coated out of the silicon dioxide film  202 . However, other etchant may be used for the etching, or dry etching may be performed for the etching.  
      After the etching of the silicon dioxide film  202 , the photoresist  203  is removed. Here, the removal of the photoresist  203  may be performed by dry etching or wet etching.  
       FIG. 6B  shows the silicon substrate  201  etc. in  FIG. 6A  viewed from the top side. As shown in  FIG. 6B , in the portion where the diamond tip  110  will be formed later, a window at which the silicon dioxide film  202  is not coated can be seen, and the silicon substrate  201  can be seen at the window.  
      Then, as shown in  FIG. 7A , anisotropic etching is performed with respect to the silicon substrate  201 . Here, for example, alkaline etchant, such as TMAH (TetraMethyl Ammonium Hydroxide) and KOH (Potassium Hydroxide), is used for the anisotropic etching.  
      Here, the silicon substrate  201  has such a property that the etching can be performed in the normal direction of the ( 100 ) surface (i.e. a direction perpendicular to the silicon substrate  201  in  FIG. 7A ), but it is relatively difficult to perform the etching in the normal direction of the ( 111 ) surface (i.e. a direction of injecting at approximately 45 degrees with respect to the silicon substrate  201  in  FIG. 7A ). To perform the anisotropic etching by using this property, the silicon substrate  201  is etched such that it has a shape corresponding to the diamond tip  110  (i.e. a projection shape or pyramid shape).  
      Incidentally,  FIG. 7B  shows the silicon substrate  201  etc. in  FIG. 7A  viewed from the top side. The anisotropic etching is performed with respect to the silicon substrate  201 , as shown in  FIG. 7B , and an etching rate is lower in a position closer to the outer portion of the window of the silicon dioxide film  202 , and the etching rate is higher in a position closer to the center of the window. As a result, the hole formed by the etching has a sharp, pointed shape.  
      Then, as shown in  FIG. 8A , the photoresist  203  is coated again for patterning.  
      Incidentally,  FIG. 8B  shows the silicon substrate  201  etc. in  FIG. 8A  viewed from the top side. As shown in  FIG. 8B , the photoresist  203  in this case is patterned in accordance with the shape of the support member  130 .  
      Then, as shown in  FIG. 9A , etching is performed with respect to the silicon dioxide film  202  in accordance with the patterning of the photoresist  203  as shown in  FIG. 8 , and then, the photoresist  203  is removed. The etching here is performed in the same procedure as in  FIG. 6 .  
      Incidentally,  FIG. 9B  shows the silicon substrate  201  etc. in  FIG. 9A  viewed from the top side. As shown in  FIG. 9B , the silicon dioxide film  202  remains in accordance with the shape of the support member  130 .  
      Then, as shown in  FIG. 10 , in methanol containing diamond powders, the surfaces of both the silicon substrate  201  and the silicon dioxide film  202  formed thereon are scratched, by vibrating the diamond powders by using ultrasound or the like, for example. By scratching the surfaces as described above, diamond nuclei can be formed in the following process (refer to  FIG. 11 ).  
      Then, as shown in  FIG. 11 , a diamond film is grown by Hot Filament CVD (Chemical Vapor Deposition). For example, using CH 4  (methane) gas as a material, the diamond film is formed on the silicon substrate  201 . In particular, the diamond film grows at the position of the scratch which is made in the process in  FIG. 10 . Incidentally, not only Hot Filament CVD, but also Microwave Plasma CVD or other film growth methods or the like may be used to grow the diamond film.  
      Moreover, the diamond film is used as the above-described diamond tip  110 , so that it requires electric conductivity. Therefore, B (Boron) is doped into the diamond film by adding a doping gas, such as B 2 H 6  (diborane) and (CH 3 O) 3 B (trimethoxy boron).  
      Incidentally, the method of growing the diamond film is not limited to the one by the scratch process as shown in  FIG. 10 . The diamond film may be grown by applying a negative bias voltage to the silicon substrate  201  at the initial stage of the CVD process, or by applying ultra micro diamond powders to the silicon substrate  201 , to thereby use the ultra micro diamond powders as the nuclei for growing the diamond film.  
      Then, as shown in  FIG. 12 , diamond particles which are growing on the silicon dioxide film  202  are removed. The removal of an extremely small amount of silicon dioxide film  202  by way of etching with BHF or the like can result in the removal of the diamond particles. By this, it is possible to form the diamond tip  110  and the support member  130  which have appropriate shapes.  
      Then, as shown in  FIG. 13 , the diamond film is further grown by using Hot Filament CVD or the like, for example, to thereby form the diamond tip  110  and the support member  130 .  
      Incidentally, in this case, the support member  130  and the diamond tip  110  are formed in one body, so that in the explanation below, the diamond tip  110  shall include a function as the support member  130 .  
      Then, after the diamond tip  110  is formed, etching is performed, as shown in  FIG. 14 , and the silicon dioxide film  202  is removed. Here, for example, BHF or the like is used to remove the silicon dioxide film  202 .  
      Then, as shown in  FIG. 15A , photosensitive polyimide  205  is formed on a surface opposite to the side where the portion corresponding to the diamond tip  110  is formed, in the portion corresponding to the support member  130 . The photosensitive polyimide  205  is used for attachment to a glass  206  (refer to  FIG. 16 ) for supporting or maintaining the entire recording/reproducing head in a later process.  
      Incidentally,  FIG. 15B  shows the silicon substrate  201  etc. in  FIG. 15A  viewed from the top side. As shown in  FIG. 15B , the photosensitive polyimide  205  is patterned on a portion opposite to a portion extending in the longitudinal direction out of the portion corresponding to the support member  130  (i.e. on a support base  130   a ).  
      Incidentally, with respect to the specific size of the recording/reproducing head shown in  FIG. 15B , the portion extending in the longitudinal direction is preferably 50 μm or less wide. Then, preferably, the portion opposite to the portion extending in the longitudinal direction is approximately 5 mm&gt;×1˜1.5 mm. However, they are not limited to the above size. With respect to the shape thereof, it is not limited to a T-shape as shown in  FIG. 15B , but it may be other shapes such as a L-shape.  
      In this case, the support member  130  is unified with a support base  130   a . The support base  130   a  is fixed, and the support member  130  is unified with the support base  130   a  such that the support member  130  can move (or wobble or oscillate) slightly as a cantilever in accordance with its elasticity. Even in this case, the support member  130  and the support base  130   a  may be collectively referred to as the support member  130 .  
      Then, as shown in  FIG. 16A , the glass  206  to which a groove-cutting process is performed is attached to the photosensitive polyimide  205 . The glass  206  is a member for supporting or maintaining the entire recording/reproducing head. By connecting an actuator or the like to the glass  206 , it is possible to displace the recording/reproducing head on or above the dielectric recording medium, in the recording and reproduction operations of the dielectric recording/reproducing apparatus described later.  
      Incidentally, the groove-cutting machining is performed to the glass  206 , by forming a cut in the vicinity of the center of the glass  206 . This is formed to easily break the glass  206  in a process described later (refer to  FIG. 18 ).  
      Incidentally,  FIG. 16B  shows the silicon substrate  201  etc. in  FIG. 16A  viewed from the top side. As shown in  FIG. 16B , the glass  206  is large enough to cover the whole diamond tip  110 . However, the size of the glass  206  shown in  FIG. 16B  is merely an example. Even if the glass  206  is larger than or smaller than this size, it is enough if it has a size to support the entire recording/reproducing head.  
      Then, as shown in  FIG. 17 , the silicon substrate  201  is removed. Here, the silicon substrate  201  is removed from the diamond tip  110  by using RIE (Reactive Ion Etching). However, other methods may be also used to remove the silicon substrate  201 .  
      Then, as shown in  FIG. 18 , the glass  206  is broken along the cut, to make the finished product available as the probe  11  described later. The processes until this correspond to one specific example of the “first forming process” in the present invention.  
      Then, afterward, the conductive film  120  is formed on the surface of the diamond tip  110  and the support member  130  (i.e. the “second forming process” in the present invention). And then the tip of the diamond tip  110  is exposed (i.e. the “exposing process” in the present invention). Incidentally, there are shown three methods to explain in the embodiment.  
      At first, a first method will be explained. As shown in  FIG. 19A , a film of metal, which has electric conductivity, is formed on the surface on the bottom side of the diamond tip  110  and the support member  130  (i.e. the surface on the side where the glass  206  etc. are not attached). For example, a deposition method may be used to form the film of metal (i.e. the conductive film  120 ) on the entire surface on the bottom side of the diamond tip  110  and the support member  130 .  
      As the conductive film  120 , for example, alloy, such as platinum palladium and platinum iridium, can be used, as described above. Incidentally, in order to increase the adherence of the alloy with respect to the diamond tip  110 , it is preferable that after a foundation, such as titanium, is deposited, the alloy is deposited, to form the conductive layer  120 . By this, it is possible to increase the adherence between the conductive film  120  and the diamond tip  110 , to thereby produce the recording/reproducing head which is more highly resistant to the deterioration such as abrasion.  
      Then, as shown in  FIG. 19B , a pulse voltage is applied to between the tip of the diamond tip  110  and an electrode  207 , which is prepared separately. Namely, pulse discharge is performed. As a result a part of the conductive film  120  formed on the tip portion of the diamond tip  110  is exfoliated or peeled off. By this, it is possible to produce such a recording/reproducing head  100  that the tip of the diamond tip  110  protrudes from the conductive film  120 , as shown in  FIG. 1A .  
      Moreover, by controlling the pulse voltage which is applied, it is possible to control the amount and shape of the part of the conductive film  120  which is exfoliated from the tip. Incidentally, it is possible to produce such a recording/reproducing head  101  that the tip portion of the diamond tip  110  is rounded, as shown in  FIG. 1C , or such a recording/reproducing head  102  that the surface of the tip portion of the diamond tip  110  is located on the same surface as the edge portion of the conductive film  120 .  
      Next, a second method will be explained. The same procedure is performed until the deposition of the conductive film  120 , as in the first method described above. Then, as shown in  FIG. 19C , the tip portion of the diamond tip  110  is moved on a grinding or polishing plate  208 , especially along the surface of the grinding or polishing plate  208 , to thereby grind, polish or exfoliate the conductive film  120  which is formed on the tip. By this, it is possible to produce the recording/reproducing head  102  shown in  FIG. 2A . Moreover, by changing the grinding or polishing direction, or by grinding or polishing while changing the inclination of the recording/reproducing head, it is possible to produce the recording/reproducing head  100  shown in  FIG. 1A  or the recording/reproducing head  101  shown in  FIG. 1C .  
      Next, a third method will be explained. As shown in FIG.  20 A, the photoresist  203  is coated onto the tip portion of the diamond tip  110 . Then, as shown in  FIG. 20B , with respect to the surface on the bottom side of the diamond tip  110  and the support member  130  after the coating of the photoresist  203 , the conductive film  120  is deposited. The deposition at this time is performed in the same method as the above-described deposition shown in  FIG. 19A .  
      Then, as shown in  FIG. 20C , by removing the photoresist  203 , it is possible to produce the recording/reproducing head  100  shown in  FIG. 1A .  
      Incidentally, the production method for the recording/reproducing head in the embodiment, which is explained in  FIG. 3  to  FIG. 20 , is merely one specific example, and it is possible to change raw materials, various methods (i.e. the etching method, the film formation method and the film growth method), or the like used in each process, as occasion demands.  
     (2) Embodiment of Recording/Reproducing Apparatus  
      Next, the recoding/reproducing apparatus which uses the recording/reproducing head in the embodiment described above will be explained.  
      (i) Basic Structure  
      At first, the basic structure of the dielectric recording/reproducing apparatus in the embodiment will be explained with reference to  FIG. 21 .  FIG. 21  conceptually shows the basic structure of the dielectric recording/reproducing apparatus in the embodiment.  
      The dielectric recording/reproducing apparatus  1  is provided with: the probe  11  for applying an electric field with its tip portion facing a dielectric material  17  of the dielectric recording medium  20 ; a return electrode  12  for returning the high-frequency electric field for reproduction applied from the probe  11 ; an inductor L placed between the probe  11  and the return electrode  12 ; an oscillator  13  which oscillates at a resonance frequency determined from the inductor L and a capacitance Cs in a portion formed in the dielectric material  17  under the probe  11  and polarized correspondingly to the record information; the alternating current (AC) signal generator  21  for applying an alternating electric field which is intended to detect the polarization condition recorded in the dielectric material  17 ; the record signal generator  22  for recording the polarization condition into the dielectric material  17 ; a switch  23  for switching outputs from the AC signal generator  21  and the record signal generator  22 ; a High Pass Filter (HPF)  24 ; a demodulator  30  for demodulating a FM signal modulated by the capacitance Cs corresponding to the polarization condition owned by the dielectric material  17  under the probe  11 ; a signal detector  34  for detecting data from the demodulated signal; a tracking error detector  35  for detecting a tracking error signal from the demodulated signal; and so on.  
      As the probe  11 , the recording/reproducing head  100  in the embodiment described above is used. Out of the probe  11 , the conductive film  120  is connected to the oscillator  13  via the HPF  24 , and connected to the AC signal generator  21  and the record signal generator  22  via the HPF  24  and the switch  23 . Then, the probe  11  functions as an electrode for applying an electric field. Incidentally, as the probe  11 , for example, a cantilever shape or a needle shape, as in  FIG. 1  and  FIG. 2 , and the like are known as its specific shape.  
      Incidentally, it is also possible that a plurality of probes  11  are provided. In this case, a plurality of AC signal generators  21  are preferably provided for the respective probes  11 . Moreover, in order to distinguish, on the signal detector (detectors)  34 , reproduction signal corresponding to each of a plurality of AC signal generators  21 , it is preferable that a plurality of signal detectors  34  are provided and that each of the signal detectors  34  obtains reference signal from the corresponding AC signal generator  21 , to thereby output the corresponding reproduction signal.  
      In the case that the plurality of probes  11  are provided, it is required that the diamond tips  110  and the conductive films  120  are insulated for each probe  11 . Then, if the support members  130  have electric conductivity, it is also required that the support members  130  are also insulated. If the support members  130  do not have electric conductivity, the support member  130  common to the diamond tips  110  and the conductive films  120  of each probe  11  may be provided.  
      The return electrode  12  is an electrode for returning the high-frequency electric field applied to the dielectric material  17  from the probe  11  (i.e. a resonance electric field from the oscillator  13 ), and is placed to surround the probe  11 . Incidentally, the shape and placement of the return electrode  12  can be arbitrarily set as long as the high-frequency electric field can return to the return electrode  12 .  
      The inductor L is placed between the probe  11  and the return electrode  12 , and may be formed using a microstripline, for example. The inductor L and the capacitance Cs constitute the resonance circuit  14 . The inductance of the inductor L is determined such that this resonance frequency is approximately 1 GHz, for example.  
      The oscillator  13  is an oscillator which oscillates at the resonance frequency determined from the inductor L and the capacitance Cs. The resonance frequency varies, depending on the change of the capacitance Cs. Therefore, FM modulation is performed correspondingly to the change of the capacitance Cs determined by the polarization domain corresponding to the recorded data. By demodulating this FM modulation signal, it is possible to read the data recorded in the dielectric recording medium  20 .  
      Incidentally, as described in detail later, the probe  11 , the return electrode  12 , the oscillator  13 , the inductor L, the HPF  24 , and the capacitance Cs in the dielectric material  17  constitute the resonance circuit  14 . The FM signal amplified on the oscillator  13  is outputted to the demodulator  30 .  
      The AC signal generator  21  applies an alternating electric field to between the return electrode  12  and an electrode  16 . The frequency of the alternating electric field is approximately 5 kHz, and the alternating electric field is applied to the domain of the dielectric material  17 . In the dielectric recording/reproducing apparatus having the plurality of proves  11 , the frequencies of the alternating electric fields are used as reference signals in the signal detector (detectors)  34  to distinguish reproduction signals detected with the probes  11 .  
      The record signal generator  22  generates a signal for recording (hereinafter referred to as a “record signal”), which is supplied to the probe  11  at the time of recording. This record signal is not limited to a digital signal but may be an analog signal. This record signal includes various signals, such as audio data, video data, and digital data for a computer. An AC signal which is superimposed to the record signal is used, as a reference signal in the reproduction operation, to distinguish and reproduce the reproduction signal of each probe  11 .  
      The switch  23  selects its output to supply an AC signal (the alternating electric field) from the AC signal generator  21  at the time of reproducing, or a record signal from the record signal generator  22  at the time of recording, to the probe  11 . A mechanical relay or a semiconductor circuit may be used for this device. In the case of the analog signal, the relay is preferably provided, and in the case of the digital signal, the semiconductor circuit is preferably provided.  
      The HPF  24  includes an inductor and a condenser. The HPF  24  is used to constitute a high pass filter for cutting off a signal system to prevent the signals obtained from the AC signal generator  21  and the record signal generator  22  from interfering with the oscillation of the oscillator  13 . The cut-off frequency is f=1/{2π√{square root over ( )}(LC)}, wherein L is the inductance of the inductor included in the HPF  24 , and C is the capacitance of the condenser included in the HPF  24 . The frequency of the AC signal is approximately 5 KHz, and the resonance frequency of the oscillator  13  is approximately 1 GHz, so that the separation at a first LC filter can be performed sufficiently. A higher-order filter may be used, but since the number of elements increases, the size of the apparatus may be increased.  
      The demodulator  30  demodulates the resonance frequency of the oscillator  13 , which is FM-modulated due to the small change of the capacitance Cs, and reconstructs a waveform corresponding to the polarized condition of a portion which is traced by the prove  11 . If the recorded data are digital data of “0” and “1”, there are two types of frequencies which are modulated, and the data is reproduced easily by distinguishing the frequencies.  
      The signal detector  34  reproduces the recorded data from the signal demodulated on the demodulator  30 . A lock-in amplifier is used as the signal detector  34 , for example, and synchronized detection is performed on the basis of the frequency of the alternating electric field of the AC signal generator  21 , to thereby reproduce the data. Incidentally, it is obvious that other phase detection devices may be used.  
      The tracking error detector  35  detects a tracking error signal for controlling the apparatus (especially, tracking operation), from the signal demodulated on the demodulator  30 . The detected tracking error signal is inputted into a tracking mechanism for the control.  
      Next, one example of the dielectric recording medium  20  shown in  FIG. 21  will be explained with reference to  FIG. 22A  and  FIG. 22B .  FIG. 22A  and  FIG. 22B  conceptually show one example of the dielectric recording medium  20  used in the embodiment.  
      As shown in  FIG. 22A , the dielectric recording medium  20  is a disc-shaped dielectric recording medium, and is provided with: a center hole  10 , an inner area  7 , a record area  8 , and an outer area  9  The inner area  7 , the record area  8 , and the outer area  9  are placed concentrically from the center hole  10  in this order. The center hole  10  is used in the case where the dielectric recording medium  20  is mounted on a spindle motor or the like.  
      The record area  8  is an area to record the data therein and has tracks and spaces between the tracks. Moreover, on the tracks and the spaces, such areas are provided that record therein control information associated with the record and reproduction. Furthermore, the inner area  7  and the outer area  9  are used to recognize the inner position and the outer position of the dielectric recording medium  20 , respectively, and can be used as areas to record therein information about the data which is recorded, such as a title, its address, a recording time length, and a recording capacity. Incidentally, the above-described construction is one example of the dielectric recording medium  20 , and other construction, such as a card-shape, can be also adopted.  
      Moreover, as shown in  FIG. 22B , the dielectric recording medium  20  is formed such that the electrode  16  is laminated on a substrate  15  and that the dielectric material  17  is laminated on the electrode  16 .  
      The substrate  15  is Si (silicon), for example, which is a preferable material in its strength, chemical stability, workability, or the like. The electrode  16  is intended to apply an electric field between the electrode  16  and the probe  11  (or the return electrode  12 ). By applying such an electric field to the dielectric material  17  that is greater than the coercive electric field of the dielectric material  17 , the polarization direction is determined. By determining the polarization direction in accordance with the data, the record operation is performed.  
      The dielectric material  17  is formed by using a known technique, such as spattering method of LiTaO 3  or the like, which is a ferroelectric substance, onto the electrode  16 . The record operation is performed with respect to such a Z surface of LiTaO 3  that the plus and minus surfaces of the polarization have a 180-degree domain relationship. It is obvious that other dielectric materials may be used. The dielectric material  17  forms the small polarization at high speed by using a direct current bias voltage and a voltage for the data which are both applied at the same time.  
      Alternatively, as the shape of the dielectric recoding medium  20 , for example, there are a disc shape and a card shape and the like. The displacement of the relative position with the probe  11  is performed by the rotation of the dielectric recording medium  20 , or by displacing linearly either the probe  11  or the dielectric recording medium  20 .  
      (ii) Operation Principle  
      Next, with reference to  FIG. 23  and  FIG. 24 , the operation principle of the dielectric recording/reproducing apparatus  1  in the embodiment will be explained. Incidentally, in the explanation below, apart of the constituent elements of the dielectric recoding/reproducing apparatus  1  shown in  FIG. 21  is extracted and explained.  
      (Record Operation)  
      At first, with reference to  FIG. 23 , the record operation of the dielectric recording/reproducing apparatus  1  in the embodiment will be explained.  FIG. 23  conceptually shows the record operation of recording the information.  
      As shown in  FIG. 23 , by applying an electric field which is greater than the coercive electric field of the dielectric material  17  to between the probe  11  and the electrode  16 , the dielectric material  17  is polarized having directions corresponding to the direction of the applied electric field. Then, by controlling an applied voltage (an applied electric field) to change the polarization direction, it is possible to record predetermined information. This uses such a property that the polarization direction is reversed when an electric field greater than the coercive electric field of a dielectric substance (particularly, a ferroelectric substance) is applied to the dielectric substance and that the polarization direction is maintained after stopping applying the electric field.  
      For example, it is assumed that the domains have a downward polarization P when an electric field is applied from the probe  11  to the electrode  16 , and that the domains have an upward polarization P when an electric field is applied from the electrode  16  to the probe  11 . This corresponds to a condition where the information is recorded. If the probe  11  is moved in a direction shown with the arrow, a detection voltage is outputted as a rectangular wave having a high level or a low level (i.e. the digital signal), correspondingly to the polarization P. Incidentally, this level varies depending on the extent of the polarization P, to thereby allow the recording as the analog signal.  
      Particularly in the embodiment, the path of an electric field is formed close to the tip portion of the probe  11  (i.e. the tip portion of the diamond tip  110 ), via the conductive film  120  constituting the probe  11 , and the electric filed is applied to (or from) the dielectric material  17  from (or to) the tip portion of the diamond tip  110 . Namely, it is possible to shorten the path of the electric field passing through the diamond tip  110 , to thereby reduce the electric resistance value of the probe  11 . In addition, as descried above, the deterioration resistance of the probe  11  is increased, so that it is possible to inhibit the deterioration caused by contact with the dielectric material  17  or the like, and it is also possible to extend the lifetime of use of the probe  11 .  
      (Reproduction Operation)  
      Next, with reference to  FIG. 24 , the reproduction operation of the dielectric recording/reproducing apparatus  1  in the embodiment will be explained.  FIG. 24  conceptually shows the reproduction operation of reproducing the information.  
      The non-linear dielectric constant of a dielectric substance changes correspondingly to the polarization direction of the dielectric substance. The non-linear dielectric constant of the dielectric substance can be detected as a difference in the capacitance of the dielectric substance or a difference in the change of the capacitance, when an electric field is applied to the dielectric substance. Therefore, by applying an electric field to a dielectric material and detecting, at that time, a difference in the capacitance Cs or a difference in the change of the capacitance Cs in a certain domain of the dielectric material, it is possible to read and reproduce the data recorded as the polarization direction of the dielectric material.  
      Specifically, at first, as shown in  FIG. 24 , an alternating electric field from the not-illustrated AC signal generator  21  is applied to between the electrode  16  and the probe  11 . The alternating electric field has such an electric field strength that is not beyond the coercive electric field of the dielectric material  17 , and has a frequency of approximately 5 kHz, for example. The alternating electric field is generated mainly to distinguish the difference in the change of the capacitance corresponding to the polarization direction of the dielectric material  17 . Incidentally, in place of the alternating electric field, a direct current bias voltage may be applied to form an electric field in the dielectric material  17 . The application of the alternating electric field causes the generation of an electric field in the dielectric material  17  of the dielectric recording medium  20 .  
      Then, the probe  11  is approached to the recording surface until the distance between the tip of the probe  11  and the recording surface becomes extremely small on the order of nanometers. Under this condition, the oscillator  13  is driven. Incidentally, in order to detect the capacitance Cs of the dielectric material  17  under the probe  11  highly accurately, it is preferable to contact the probe  11  with the surface of the dielectric material  17 , i.e. the recording surface. However, in order to read the data recorded in the dielectric material  17  at high speed, it is necessary to relatively displace the probe  11  on the dielectric recording medium  20  at high speed. Thus, in view of reliability in the high-speed displacement, and the prevention of damage caused by the collision and friction between the probe  11  and the dielectric recording medium  20 , or the like, it is practically better to make the probe  11  approach the recording surface close enough to regard this as the actual contact (i.e. substantially contact), than make the probe  11  contact the recording surface.  
      Particularly in the embodiment, as shown in  FIG. 1  and  FIG. 2 , the probe  11  is shaped such that the diamond tip  110  protrudes at the tip portion of the probe  11 . Or the probe  11  is shaped such that the diamond tip  110  (especially, the tip portion of the diamond tip  110 ) prevents the deterioration of the conductive film  120  such as the abrasion. Therefore, even if the probe  11  directly contacts the dielectric recording medium  20 , it is no problem in view of the deterioration caused by the abrasion of the probe  11  or the like.  
      Then, the oscillator  13  oscillates at the resonance frequency of the resonance circuit, which includes the inductor L and the capacitance Cs associated with the dielectric material  17  under the probe  11  as the constituent factors. The central frequency of the resonance frequency is set to approximately 1 GHz, as described above.  
      Here, the return electrode  12  and the probe  11  constitute a part of the resonance circuit  14  including the oscillator  13 . The high-frequency signal of approximately 1 GHz, which is applied to the dielectric material  17  from the probe  11 , passes through the dielectric material  17  and returns to the return electrode  12 , as shown with solid lines in  FIG. 24 . By placing the return electrode  12  in the vicinity of the probe  11  and shortening a feedback route to the resonance circuit  14  including the oscillator  13 , it is possible to reduce a chance of noise (e.g. floating capacitance) entering the resonance circuit  14 .  
      In addition, the change of the capacitance Cs corresponding to the non-linear dielectric constant of the dielectric material  17  is extremely small, and in order to detect this change, it is necessary to adopt a detection method having high detection accuracy. In a detection method using FM modulation, generally, it is possible to achieve the high detection accuracy, but it is necessary to further improve the detection accuracy to likely detect the small capacitance change corresponding to the non-linear dielectric constant of the dielectric material  17 . Thus, in the dielectric recording/reproducing apparatus  1  in the embodiment (i.e. a recording/reproducing apparatus which uses the SNDM principle), the return electrode  12  is placed in the vicinity of the probe  11  to shorten the feedback route (the feedback path) to the resonance circuit  14  as much as possible. By this, it is possible to obtain extremely high detection accuracy, and thus it is possible to detect the small capacitance change corresponding to the non-linear dielectric constant of the dielectric substance.  
      After the oscillator  13  is driven, the probe  11  is displaced in parallel with the recording surface on the dielectric recording medium  20 . By the displacement, the domain of the dielectric material  17  under the probe  11  is changed, and whenever its polarization direction changes, the capacitance Cs changes. If the capacitance Cs changes, the resonance frequency (the oscillation frequency) of the oscillator  13  changes. As a result, the oscillator  13  outputs a signal which is FM-modulated on the basis of the change of the capacitance Cs.  
      This FM signal is frequency-voltage converted by the demodulator  30 . As a result, the change of the capacitance Cs is converted to the change of a voltage. The change of the capacitance Cs corresponds to the non-linear dielectric constant of the dielectric material  17 . The non-linear dielectric constant corresponds to the polarization direction of the dielectric material  17 . The polarization direction corresponds to the data recorded in the dielectric material  17 . Therefore, a signal obtained from the demodulator  30  is a signal whose voltage changes correspondingly to the data recorded in the dielectric recording medium  20 . Moreover, the signal obtained from the demodulator  30  is supplied to the signal detector  34 , and the data recorded in the dielectric recording medium  20  is extracted by the synchronized detection, for example.  
      At this time, in the signal detector  34 , the AC signal generated by the AC signal generator  21  is used as a reference signal. This makes it possible to extract the data highly accurately, by referring the reference signal (i.e. synchronizing with the reference signal), as described above, even if the signal obtained from the demodulator  30  includes much noise or the data to be extracted is weak, for example.  
      Particularly, in the embodiment, the recording/reproducing head shown in  FIG. 1  and  FIG. 2  is used as the probe  11 . Therefore, it is possible to reduce the electric resistance value of the probe  11 , to thereby reduce the electric resistance in the resonance circuit  14 . By this, it is possible to inhibit the attenuation of a signal flown in the resonance circuit  14 , and it is possible to reproduce the data more stably. Moreover, since the deterioration resistance of the probe  11  is high, it is possible to extend the lifetime of use of the probe  11 .  
      Moreover, in the above-described embodiment, the dielectric material  17  is used for a recording layer, but from the viewpoint of the presence or absence of spontaneous polarization and the non-linear dielectric constant, the dielectric material  17  is preferably a ferroelectric substance.  
      The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.  
      The entire disclosure of Japanese Patent Application No. 2003-412223 filed on Dec. 10, 2003 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.