Abstract:
An ultra-high-density data storage device including at least one energy-channeling component and a storage medium that usually includes at least one rectifying junction region. The energy-channeling component is generally capable of emitting such energies as, but not limited to, thermal, optical and electronic energy. The energy-channeling component is generally located either within close proximity of or in direct contact with the storage medium. The storage medium typically includes nanometer-scaled storage areas.

Description:
FIELDS OF THE INVENTION 
     The present invention relates to a data storage device capable of storing, reading and writing data to data storage areas of nanometer dimensions. 
     BACKGROUND OF THE INVENTION 
     Recently, scientists have been developing alternative ultra-high-density data storage devices and techniques useful for operating ultra-high-density data storage devices. These devices and techniques store data bits within storage areas sized on the nanometer scale and possess advantages over conventional data storage devices. Among these advantages are quicker access to the data bits, a lower cost per bit and enablement of the manufacturing of smaller electronic devices. 
     FIG. 1 illustrates an ultra-high-density data storage device configuration according to the related art that includes a storage medium  40  that is separated into many storage areas (illustrated as squares on the storage medium  40 ), each capable of storing one data bit. Two types of storage areas, unmodified regions  140  that typically store data bits representing the value “0” and modified regions  130  that typically store data bits representing the value “1”, are illustrated in FIG.  1 . Typical periodicities between any two storage areas in these devices range between 1 and 100 nanometers. 
     FIG. 1 also shows, conceptually, emitters  350  positioned above the storage medium  40 , and a gap between the emitters  350  and the storage medium  40 . The emitters  350  are capable of emitting electron beams and are arranged on a movable emitter array support  360  (also known as a “micromover”) that can hold hundreds or even thousands of emitters  350  in a parallel configuration. The emitter array support  360  provides electrical connections to each emitter  350  as illustrated conceptually by the wires on the top surface of emitter array support  360 . 
     The emitter array support  360  can move the emitters  350  with respect to the storage medium  40 , thereby allowing each emitter  350  to scan across many storage areas on the storage medium  40 . In the latter case, the storage medium  40  can be placed on a platform that moves the storage medium  40  relative to the emitter array support  360 . The platform can be actuated electrostatically, magnetically or by the use of piezoelectrics and, dependent upon the range of motion between the emitter array support  360  relative to the storage medium  40 , each emitter  350  can have access to data bits in tens of thousands or even millions of data storage areas. 
     Related Art: (Ultra-High Density Data Storage Devices) 
     Some specific embodiments of the ultra-high-density data storage device discussed above are disclosed in U.S. Pat. No. 5,557,596 to Gibson et al. (Gibson &#39;596), the contents of which are incorporated herein in their entirety by reference. 
     The devices disclosed in the Gibson &#39;596 patent include a storage medium  40  with modified regions  130  and unmodified regions  140 , emitters  350  and an emitter array support  360 . The Gibson &#39;596 devices provide a relatively inexpensive and convenient method for producing ultra-high-density data storage devices that can be manufactured by well-established and readily-available semiconductor processing technology and techniques. Further, some of the devices disclosed in the Gibson &#39;596 patent are somewhat insensitive to emitter noise and variations in the gap distance between the emitters  350  and the storage medium  40  that may occur when the emitters  350  move relative to the storage medium  40  during device operation. Reasons for these insentivities are related, for example, to the nature of the diode devices disclosed in the Gibson &#39;596 because the diodes allow constant current sources to be connected to the emitters  350  and allow the electron beam energy to be monitored independently of the signal current in order to normalize the signal as described in the Gibson &#39;596 patent. However, the devices disclosed in the Gibson &#39;596 patent must be operated under stringent vacuum conditions. 
     The storage medium  40 , according to the Gibson &#39;596 patent, can be implemented in several forms. For example, the storage medium  40  can be based on diodes such as p-n junctions or Schottky barriers. Further, the storage medium  40  can include combinations of a photodiode and a fluorescent layer such as zinc oxide. This type of configuration relies on monitoring changes in the cathodoluminescence of the storage medium  40  to detect the state of a written bit. Also, according to the Gibson &#39;596 patent, the storage medium  40  can be held at a different potential than the emitters  350  in order to accelerate or decelerate electrons emanating from the emitters  350 . 
     The emitters  350  disclosed in the Gibson &#39;596 patent are electron-emitting field emitters made by semiconductor micro-fabrication techniques and emit very narrow electron beams. These can be silicon field emitters but can also be Spindt emitters that typically include molybdenum cone emitters, corresponding gates and a pre-selected potential difference applied between each emitter and its corresponding gate. The Gibson &#39;596 patent also discloses electrostatic deflectors that sometimes are used to deflect the electron beams coming from the emitters  350 . 
     According to the Gibson &#39;596 patent, the emitter array support  360  can include a 100×100 emitter  350  array with an emitter  350  pitch of 50 micrometers in both the X- and Y-directions. The emitter array support  360 , like the emitters  350 , can be manufactured by standard, cost-effective, semiconductor micro-fabrication techniques. Further, since the range of movement of the emitter array support  360  can be as much as 50 micrometers, each emitter  350  can be positioned over any of tens of thousands to hundreds of millions of storage areas. Also, the emitter array support  360  can address all of the emitters  350  simultaneously or can address them in a multiplex manner. 
     During operation, the emitters  350  are scanned over many storage areas by the emitter array support  360  and, once over a desired storage area, an emitter  350  can be operated to bombard the storage area with either a high-power-density electron beam or a low-power-density electron beam. As the gap between the emitters  350  and the storage medium  40  widens, the spot size of the electron beams also tends to widen. However, the emitters  350  must produce electron beams narrow enough to interact with a single storage area. Therefore, it is sometimes necessary to incorporate electron optics, often requiring more complicated and expensive manufacturing techniques to focus the electron beams. 
     If the emitters  350  bombard the storage areas with electron beams of sufficient power density, the beams effectively write to the storage medium  40  and change the bombarded storage areas from unmodified areas  140  to modified areas  130 . This writing occurs when electrons from the high-power-density-electron beams bombard the storage areas and cause the bombarded storage areas to experience changes of state such as changes from crystalline structures to amorphous structures or from undamaged to thermally damaged. 
     The changes of state can be caused by the bombarding electrons themselves, specifically when collisions between the electrons and the media atoms re-arranges the atoms, but can also be caused by the high-power-density-electron beams transferring the energy of the electrons to the storage areas and causing localized heating. For phase changes between crystalline and amorphous states, if the heating is followed by a rapid cooling process, an amorphous state is achieved. Conversely, an amorphous state can be rendered crystalline by heating the bombarded storage areas enough to anneal them. 
     The above writing process is preferable when the storage medium  40  chosen contains storage areas that can change between a crystalline and amorphous structure and where the change causes associated changes in the material&#39;s properties. For example, properties such as band structure, crystallography and the coefficients of secondary electron emission coefficient (SEEC) and backscattered electron coefficient (BEC) can be altered altered. According to the devices disclosed in the Gibson &#39;596 patent, these changes in material properties can be detected and allow for read operations to be performed, as will be discussed below. 
     When a diode is used as the storage medium  40 , high-power-density bombarding beams locally alter storage areas on the diode surface between crystalline and amorphous states. The fact that amorphous and crystalline materials have different electronic properties is relied upon to allow the performance of a read operation, as will be discussed further below. 
     When writing to a storage medium  40  made up of a photodiode and a fluorescent material, the emitters  350  bombard and alter the state of regions of the fluorescent material with the high-power-density-electron beams. This bombardment locally alters the densities of radiative and non-radiative recombination centers and, thereby, locally alters the light-emitting properties of the bombarded regions of the fluorescent layer and allows yet another approach, to be discussed below, for performing a read operation. 
     Once data bits have been written to the storage medium  40 , a read process can retrieve the stored data. In comparison to the high-power-density-electron beams used in the write process, the read process utilizes lower-power-density-electron beams to bombard the storage regions on the storage medium  40 . The lower-power-density-electron beams do not alter the state of the storage areas they bombard but instead either are altered by the storage medium  40  or generate signal currents therein. The amplitudes of these beam alterations or signal currents depend on the states of the storage areas (e.g., crystalline or amorphous) and change sharply dependent on whether the storage areas being bombarded are modified regions  130  or unmodified regions  140 . 
     When performing a read operation on a storage medium  40  that has storage areas that can change between a crystalline and amorphous structure and where the change causes associated changes in the material&#39;s properties, the signal current can take the form of a backscattered or secondary electron emission current made up of electrons collected by a detector removed from the storage medium. Since SEEC and BEC coefficients of amorphous and crystalline materials are different, the intensity of the current collected by the detector changes dependent on whether the lower-power-density-electron beam is bombarding a modified region  130  or an unmodified region  140 . By monitoring this difference, a determination can be made concerning whether the bombarded storage area corresponds to a “1” or a “0” data bit. 
     When a diode is chosen as the storage medium  40 , the signal current generated is made up of minority carriers that are formed when the lower-power-density electron beam bombards a storage area and excites electron-hole pairs. This type of signal current is specifically made up of those formed minority carriers that are capable of migrating across the interface of the diode and of being measured as a current. Since the number of minority carriers generated and capable of migrating across the diode interface can be strongly influenced by the crystal structure of the material, tracking the relative magnitude of the signal current as the beam bombards different storage areas allows for a determination to be made concerning whether the lower-power-density-electron beam is bombarding a modified region  130  or an unmodified region  140 . 
     In the case of a photodiode and fluorescent material used as the storage medium  40 , the lower-power-density electron beam used for reading stimulates photon emission from the fluorescent material. Dependent on whether the region bombarded is a modified region  130  (e.g., thermally modified) or an unmodified region  140 , the number of photons stimulated in the fluorescent material and collected by the photodiode will be significantly different. This leads to a different amount of minority carriers generated in the photodiode by the stimulated photons and results in a difference in the magnitude of the signal current traveling across the photodiode interface as the beam bombards different storage areas. 
     In many of the embodiments described above, a bulk-erase operation is possible to reset all of the modified regions  130  present on the storage medium  40  after the writing process. For example, if an entire semiconductor storage medium  40  is properly heated and cooled, the entire storage medium  40  can be reset to its initial crystalline or amorphous structure, effectively erasing the written data bits. With regard to a photodiode storage medium  40 , bulk thermal processing can reset thermally altered areas by processes such as annealing. 
     Related Art: Atomic Force Microscopes (AFM) 
     FIG. 2 illustrates a top view of a typical AFM probe  10  according to the related art that is made up of a tip  20 , a compliant support  30  that supports the tip  20  and that itself is supported by other components of the AFM (not shown) and a piezoelectric material  50  deposited on the top surface of the compliant suspension  30 . 
     The probe  10  can be operated in the contact, non-contact or tapping (intermittent contact) AFM modes that are well known in the art and that will only briefly be discussed here. The contact mode allows for direct contact between the tip  20  and the storage medium  40  while the non-contact mode (not shown) keeps the tip  20  in close proximity (generally on the order of or less than approximately 100 nanometers) to the storage medium  40 . The tapping mode allows the compliant suspension  30  to oscillate in a direction perpendicular to the surface of the storage medium  40  while the probe  10  moves in a direction parallel relative to the storage medium  40  and the tip  20  therefore contacts or nearly contacts the storage medium  40  on an intermittent basis and moves between positions that are in direct contact with and in close proximity to the storage medium  40 . 
     The tip  20  is typically, although not exclusively, made from silicon or silicon compounds according to common semiconductor manufacturing techniques. Although the tip  20  is typically used to measure the dimensions of surface features on a substrate such as the storage medium  40  discussed above, the tip  20  can also be used to measure the electrical properties of the storage medium  40 . 
     As stated above, the tip  20  in FIG. 2 is affixed to a compliant suspension  30  that is sufficiently flexible to oscillate as required by the intermittent contact or tapping mode or as required to accommodate unwanted, non-parallel motion of the tip suspension with respect to the storage medium during scanning (so as to keep the tip in contact or at the appropriate working distance). The compliant suspension  30  typically holds the tip  20  at one end and is attached to and supported by the remainder of the AFM or STM structure on the other end. Storage medium  40 , in a typical AFM structure, rests on a platform that is moved with relation to the tip  20 , allowing the tip  20  to scan across the storage medium  40  as the platform moves. 
     FIG. 2 illustrates a piezoelectric material  50  deposited on the top surface of the compliant suspension  30 . As the tip  20  moves across the storage medium  40 , the tip  20  moves the compliant suspension  30  up and down according to the surface variations on the storage medium  40 . This movement, in turn, causes either compression or stretching of the piezoelectric material  50  and causes a current to flow therein or causes a detectable voltage change. This voltage or current is monitored by a sensor (not shown) and is processed by other components of the AFM or STM to produce images of the surface topography of the scanned area. 
     Disadvantages of the Related Technology: 
     Typical ultra-high-density data storage devices, the devices disclosed by the Gibson &#39;596 patent and the AFM/STM devices described above have several shortcomings for producing high-density data storage devices. 
     For example, ultra-high-density data storage devices suffer from at least one of the following disadvantages: relatively small signal currents, relatively large beam spot sizes and relatively poor signal-to-noise ratios. 
     Among the reasons for the relatively poor signal-to-noise ratio disadvantage is included the susceptibility of devices that utilize non-contact methods (e.g., field emitters or STM tips) to experiencing changes in the gap distance between the emitters  350  and the storage medium  40  as the emitters  350  move relative to the storage medium  40 . These gap-distance changes lead to intensity changes in the signal current that are not attributed to variations in the state of the bombarded storage areas and therefore add noise. 
     The relatively large spot sizes can be at least partially attributed to spreading of the beam over the gap distance. In order to obtain smaller spot sizes, electron optics are sometimes used to focus the electron beams. However, such configurations have the disadvantage of being more complex and therefore often more difficult and costly to manufacture. 
     Other disadvantages of current ultra-high-density storage devices that utilize non-contact methods are that they do not allow for the gap distance between the storage medium  40  and the emitters  350  to be controlled passively. Rather, because the emitters  350  are not in direct contact with the storage medium  40 , it is necessary to continuously monitor and maintain the gap distance between the emitters  350  and the storage medium  40  in order to insure that all storage areas are written to and read from with substantially the same concentration of beam electrons. 
     Yet other disadvantages of ultra-high-density data storage devices are that such devices can be required to operate at least under a partial vacuum and often operate effectively only under stringent vacuum conditions. 
     Hence, what is needed are ultra-high density devices that provide relatively large signal currents, allow relatively focused beams to bombard the storage medium without necessitating costly focusing optics and provide relatively good signal-to-noise ratios of the devices. 
     What is needed are devices and methods for writing data to and reading data from a storage medium that essentially obviate the need for monitoring and dynamically controlling distances between the storage medium and the emitters of the devices or of controlling the focus of the emitters. 
     What is needed are devices and methods for writing data to and reading data from storage media that either alleviate the need for a vacuum to be drawn around the emitters or that reduce the degree of vacuum required. 
     What is needed are devices and methods for writing data to and reading data from storage media that allow for a more constant beam flux to be maintained between the emitters and the storage media. 
     What is needed are rapid, reliable, cost-effective and convenient methods of manufacturing and operating data storage devices for ultra-high-density data storage. 
     SUMMARY OF THE INVENTION 
     Certain embodiments of the present invention are directed at a data storage device including a storage medium including a rectifying junction region, at least one nanometer-scaled unmodified region near the rectifying junction region, at least one nanometer-scaled modified region near the rectifying junction region and at least one energy-emitting probe positioned within close proximity of a surface of the storage medium. 
     Certain embodiments of the present invention are also directed at a method of data storage including providing a storage medium that includes a rectifying junction region and a nanometer-scaled unmodified region, positioning an energy-channeling component within close proximity of the storage medium, and converting the nanometer-scaled unmodified region into a nanometer-scaled modified region. 
     Certain embodiments of the present invention provide ultra-high density devices that provide relatively large signal currents, allow relatively focused beams to bombard the storage medium without necessitating costly focusing optics and provide relatively good signal-to-noise ratios of the devices. 
     Certain embodiments of the present invention provide devices and methods for writing data to and reading data from storage media that either alleviate the need for a vacuum to be drawn around the emitters or that reduce the degree of vacuum required. 
     Certain embodiments of the present invention provide devices and methods for writing data to and reading data from storage media that allow for a more constant beam flux to be maintained between the emitters and the storage media. 
     Certain embodiments of the present invention provide rapid, reliable, cost-effective and convenient methods of manufacturing and operating data storage devices for ultra-high-density data storage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates an ultra-high-density data storage device according to the related art. 
     FIG. 2 illustrates a side view of an AFM probe configuration according to the related art. 
     FIG. 3 a  illustrates a side view of a data storage device according to certain embodiments of the present invention wherein an AFM contact mode of operation is used along with a first embodiment of a tip. 
     FIG. 3 b  illustrates a side view of a data storage device according to certain embodiments of the present invention wherein a cathodoconductivity measurement may be performed. 
     FIG. 4 a  illustrates a side view of certain embodiments of the present invention wherein an AFM non-contact or tapping mode of operation is used along with a tip that differs from the tip illustrated in FIG. 3 a.    
     FIG. 4 b  illustrates yet other embodiments of the present invention where the tip has a portion in contact with the storage medium and a portion offset from the storage medium. 
     FIG. 5 illustrates another embodiment of the present invention where two tips are present on the compliant suspension and where one tip contacts the storage medium whereas the other tip does not. 
     FIG. 6 a  illustrates a diode-type storage medium according to certain embodiments of the present invention. 
     FIG. 6 b  illustrates a fluorescent material/photodiode-type storage medium according to the certain embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 3 a  illustrates an energy-emitting probe  105  within the scope of certain embodiments of the present invention. Although a single probe  105  is illustrated in FIG. 3 a , certain embodiments of the present invention include ultra-high-density data storage device configurations wherein multiple probes  105  are attached to emitter array supports  360  such as those discussed above. 
     In addition to the emitter array support  360  embodiments discussed in the Gibson &#39;596 patent, certain embodiments of the present invention include emitter array support  360  configurations that are not attached to a vacuum casing, since certain embodiments of the present invention can be operated at pressures such as 1 atmosphere or other pressures above 10 −5  torr. According to these embodiments, the emitter array support  360  is supported instead either by components typically included within AFM/STM configurations or by components that one skilled in the art of the present invention would know to use in order to position the emitter array support  360  at desired locations above the storage medium  40 . Also, the probes  105  on the emitter array support  360  can write to and read from either a single storage area or can scan across up to and including millions of storage areas. Further, the emitter array support  360  configurations, according to certain embodiments of the present invention, can have ranges of motion greater than 50 microns. Even further, the storage medium  40  according to the present invention can include one or more rectifying junctions. 
     The energy-emitting probes  105  supported by the emitter array support  360  can, according to certain embodiments of the present invention, be addressed simultaneously or in a multiplexed manner and the wiring to the probes is not restricted to the single wire illustrated in FIG.  1 . Either one or a multitude of wires can be used, depending on the embodiment. 
     According to certain embodiments of the present invention, each probe  105  includes a compliant suspension  110  that has a connection  80  linking an energy source  150  to a tip  120  or other physical energy-channeling component, either directly or indirectly, from the probe  105  to the storage medium  40 . The energy source  150  allows the tip  120  to provide a localized source of energy and can, according to certain embodiments, emit a high-power-density beam capable of altering the state of the region of the storage medium  40  being bombarded by the emitted beam. In certain embodiments, the tip  120  can be in direct contact with the storage medium  40  or can be separated from the storage medium by distances typical for AFM configurations in either the non-contact or intermittent contact modes. 
     The tip  120  in certain embodiments of the present invention is capable of emitting beams of energy in forms including, but not limited to, electrons, light, heat or other energy forms capable of turning an unmodified region  140  into a modified region  130  by changing the state of the storage area as discussed above. Although the data bits discussed above are binary in the sense that they can be, for example, in either an amorphous or crystalline state or either thermally modified or unmodified, certain embodiments of the present invention include non-binary data bits where, for example, the state of the data bits can be chosen to be either amorphous or one of several crystalline states. 
     According to certain embodiments of the present invention, in addition to the storage medium  40  embodiments discussed above, p + -p junctions, n + -n junctions and rectifying junctions not specifically disclosed in the Gibson &#39;596 patent may be used. Further, according to certain embodiments, semiconducting chalcogenide reversible phase-change materials may also be used as part of the storage medium  40 . According to certain other embodiments of the present invention, direct bandgap III-VI chalcogenide-based phase change materials are preferably used. 
     Also, the storage medium  40  can be configured in a manner illustrated in FIG. 3 b  that allows for cathodoconductivity measurements to be recorded. In such embodiments of the present invention, the material making up storage medium  40  can be a cathodoconductive chalcogenide-based phase change material made of at least one of the following elements: Se, Te, S, Sb, Ag, In and Ga. 
     As illustrated in FIG. 3 b , modified regions  130  and unmodified regions  140  are positioned between electrodes  125 ,  135  that are in contact with storage medium  40 . The electrodes  125 ,  135  may be positioned above, below or to the side of the modified regions  130  and unmodified regions  140  and more than one pair of electrodes  125 ,  135  may be present in the storage medium  40 . When a bias voltage is applied to the electrodes  125 ,  135 , an electric field E is induced in the plane of the cathodoconductive storage medium  40  and a dark current flows between the electrodes  125 ,  135 . 
     When performing cathodoconductivity measurements, the modified regions  130  and unmodified regions  140  are bombarded by electron beams emitted from the tip  120 , electron carriers and hole carriers are created, the electric field E accelerates the free carriers towards the electrodes  125 ,  135  and a signal current caused by the movement of the electrons and holes can be detected by a sensor (not shown) attached to one of the electrodes. Because bombarding a modified region  130  and an unmodified region  140  leads to the creation and collection of different concentrations of carriers, a read operation is able to be performed by monitoring the amplitude of the signal current as a function the position of the tip  120 . 
     According to certain embodiments of the present invention, in addition to the emitters  350  discussed above, emitters  350  such as, but not limited to, flat cathode emitters can also be used to produce the energy beams needed to read from and write to the storage medium  40 . 
     Although the tip  120  is illustrated in FIGS. 3 a  and  3   b  as being in the contact AFM mode, the tip  120  can also be operated in non-contact and tapping AFM modes. Also, the compliant suspension  110  may take other geometries known to those skilled in the art as compatible with other components in the embodiments of the present invention. 
     In addition to the geometry of tip  120  illustrated in FIGS. 3 a  and  3   b , certain embodiments of the present invention can incorporate other component or tip geometries, some examples of which are disclosed in U.S. Pat. No. 5,936,243 to Gibson et al. (Gibson &#39;243), the contents of which are herein incorporated in their entirety by reference. The components or tips used in the embodiments of the present invention can have any geometry that one skilled in the art would know to use in practicing the present invention, and generally should be formed from materials capable of withstanding the temperature conditions experienced when channeling the high-power-density beams discussed above. 
     The components, such as tip  120  illustrated in FIGS. 3 a  and  3   b  can include a composite material with different types of grains such as, but not limited to, wear-resistant grains (to prolong the life of the tip  120  as it travels across and contacts the storage medium), wear-reducing grains (to protect against scratching of the storage medium  40 ) and conductive grains. These composite materials allow for the tip  120  to be conductive and to emit high-power-density energy beams while also providing extended lifetimes for the tip  120  and storage medium  40 . 
     Certain other embodiments of the present invention, as illustrated in FIG. 4 a , can include a sheathed tip  160 . FIG. 4 a  illustrates an energy-emitting probe  155  that can be operated in a contact, non-contact or a tapping mode. In the illustrated non-contact mode, the distance between the tip  160  and the storage medium  40  is less than 100 nanometers. In the tapping mode, a range of amplitudes and frequencies common to AFM operation may be used. 
     The tip  160  in FIG. 4 a  includes a core  170  made up of a conducting material that is capable of emitting an energy beam of sufficient power density to transform an unmodified region  140  into a modified region  130  as previously discussed. The tip  160  also includes a cladding  180  that is made up of wear-resistant or wear-reducing material and that is substantially protruding the same distance away from the compliant suspension  110  as the core  170 . 
     Among the purposes of the cladding  180  is to extend the lifetime of the tip  160  when the probe  155  is operated in either a tapping or contact AFM mode. 
     FIG. 4 b  illustrates an energy-emitting probe  215  in contact with the storage medium  40 . Although the probe  215  can also be operated in tapping and non-contact modes, in the contact mode illustrated, the contacting sheath  230  protrudes from the compliant suspension  110 . According to certain embodiments, the contacting sheath  230  protrudes approximately 100 nanometers or more further than the non-contacting core  220 . Because the contacting sheath  230  is made of wear-resistant or wear-reducing material, the contacting sheath  230  extends the lifetime of the tip  225  by not allowing the non-contacting core  220  to directly contact the storage medium  40  and to be worn away. The non-contacting core  220  emits a high-power-density energy beam and is connected to an energy source  150  (not shown). 
     When the contacting sheath  230  is in direct contact with the storage medium  40 , an advantage of certain embodiments of the present invention is attained because the emitting non-contacting core  220  is positioned at a substantially fixed distance away from the storage medium  40  as the probe  215  travels across the storage medium  40 . Hence, even though the beam emitting source is positioned at a distance away from the storage medium  40 , simpler focusing optics may be required, dependent on the particular embodiment, thereby easing the manufacturing and control process of the writing operation. In particular, no servoing is required for gap control so the focusing optics can be simplified and, in some cases, even eliminated. 
     FIG. 5 illustrates other embodiments of the present invention wherein an energy-emitting probe  185  includes two components or tips: a non-contacting, energy-channeling component or tip  190  and a contacting positioning component or tip  200 . Like the probes discussed above and below, the probe  185  can be used in any of the AFM modes discussed above as well as with any of the storage media  40  discussed previously. In essence, all of the components of all of the embodiments of the present invention disclosed herein can be mixed and matched to form other embodiments also within the scope of the present invention. 
     The contacting tip  200  is made from a wear-resistant or wear-reducing material to extend the life of the n on-contacting tip  190  that emits the energy beam and/or extends the lifetime of the storage medium. Like the contacting sheath  230 , the contacting tip  200  allows the non-contacting tip  190  to be positioned at a fixed distance relative to the storage medium  40  without requiring position monitoring and control and simplifies the requirements for beam-focusing optics. Further, when made of wear-reducing material, the contacting tip  200  reduces scratching or grooves in the storage medium  40  that may develop upon repeated read and write operation. 
     Also illustrated in FIG. 5 is a surface layer  210 , useable in conjunction with certain embodiments of the present invention illustrated in FIG.  5  and in many other embodiments of the present invention discussed above and below. Among the advantages provided by the surface layer  210  is the ability to extend the lifetime of the storage medium  40  upon repeated read and write operations. 
     The surface layer  210  may be made up of any material capable of reducing wear, evaporation/ablation or material flow, and the changes in surface topography associated therewith, of the storage medium  40 . The surface layer  210  can also be made up of any material capable of preventing contamination of any of the tips within the scope of the present invention. In certain embodiments of the present invention, the surface layer  210  can act as an electrically conductive surface electrode. In certain other embodiments, the surface layer  210  can be made from materials such as, but not limited to, silicon dioxide or alumina (Al 2 O 3 ). 
     Another advantage of the surface layer  210  is that, because the material(s) from which it is made can have higher melting temperatures than the storage medium  40 , during the write operation discussed above, the presence of the surface layer  210  prevents depositing of any storage medium  40  material onto any of the probe tips of the present invention, even when the tips are used according to the contact AFM mode. It should be noted that, especially if light is the type of energy beam being used, the surface layer  210  can be chosen from materials transparent to light and, with certain types of energy beams, one or more layers of material can be positioned between the surface layer  210  and the storage medium  40 . 
     FIG. 6 a  illustrates a storage medium  40  in the form of a diode  240  with a diode interface  290  across which minority carriers migrate. The generation of minority carriers and their migration across the diode interface  290  are analogous to the diode configuration discussed in the Gibson &#39;596 patent. Namely, a different number of carriers are generated in modified the regions  130  than in the unmodified regions  240 . Further, of those carriers generated, the collection efficiency can be different due to factors discussed in the Gibson &#39;596 patent. A total current is read across the current meter  250  and it is used to determine whether the storage area of the diode  240  bombarded is a modified region  130  or unmodified region  140 . It should be noted that the diode configuration illustrated in FIG. 6 a  can be used in conjunction with any of the probes and device components included within the embodiments of the present invention. 
     FIG. 6 b  illustrates an embodiment of the present invention wherein a photodiode  270  with a photodiode interface  300  and a fluorescent material  280  deposited on the photodiode  270  are present. Also, the above-discussed surface layer  210  is illustrated to protect the fluorescent material  280  according to certain embodiments of the present invention. According to certain embodiments of the present invention, a photodiode or photodetector can be used to monitor the stimulated photon emission due to the bombardment of the electron beam. 
     The fluorescent layer  280  of the present invention can be zinc oxide, as discussed previously, but can also be chosen from materials such as, but not limited to, direct bandgap III-VI chalcogenide-based phase change materials. The fluorescent layer  280  can be written to by the methods discussed above and in the Gibson &#39;596 patent. Additionally, the fluorescent material  280  can also be written to, according to certain embodiments of the present invention, by methods that alter the fluorescent layer  280  such that, for example, the electronic band structure of the material is modified (e.g., the material is changed from a direct band gap material to an indirect band gap material). According to certain embodiments of the present invention, the fluorescent layer  280  can also be written to by, for example, changing the wavelength of the emission, the generation rate and or the optical properties of the medium such that different amounts of light escape the material. Further, certain embodiments of the present invention write to the fluorescent layer  280  by altering the concentration of the non-radiative recombination sites. 
     According to certain embodiments of the present invention, any of the above-discussed probes or any other probe within the scope of certain embodiments of the present invention may be used to write and read to the fluorescent material  280  or any other embodiments of the storage medium  40 . During the read operation, a different number of photons are emitted from the modified regions  130  than the unmodified regions  140  of the fluorescent material  280 , leading to the generation of a different number of minority carriers crossing the photodiode interface  300 . Using the meter  250 , it is possible to determine whether the energy beam emanating from the tip of the probe used in conjunction with the photodiode configuration is bombarding a modified region  130  or an unmodified region  140 . 
     Although the above embodiments are representative of portions of the present Invention, other embodiments of the present invention will be apparent to those skilled in the art from a consideration of this specification or practice of the present invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the present invention being defined by the claims and their equivalents.