Abstract:
A field emission display includes a substrate and a plurality of emitters formed on columns on the substrate. The display also includes a porous dielectric layer formed on the substrate and the columns. The porous dielectric layer has an opening formed about each of the emitters and has a thickness substantially equal to a height of the emitters above the substrate. The porous dielectric layer may be formed by oxidation of porous polycrystalline silicon. The display also includes an extraction grid formed substantially in a plane defined by respective tips of the plurality of emitters and having an opening surrounding each tip of a respective one of the emitters. The display further includes a cathodoluminescent-coated faceplate having a planar surface formed parallel to and near the plane of tips of the plurality of emitters. The porous dielectric layer results in columns having less capacitance compared to prior art displays. Accordingly, less electrical power is required to charge and discharge the columns in order to drive the emitters. As a result, the display is able to form luminous images while consuming reduced electrical power compared to prior art displays.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to field emission displays, and, more particularly, to a method and apparatus for reducing power consumption in field emission displays.  
         BACKGROUND OF THE INVENTION  
         [0002]    [0002]FIG. 1 is a simplified side cross-sectional view of a portion of a display  10  including a faceplate  20  and a baseplate  21 , in accordance with the prior art. FIG. 1 is not drawn to scale. The faceplate  20  includes a transparent viewing screen  22 , a transparent conductive layer  24  and a cathodoluminescent layer  26 . The transparent viewing screen  22  supports the layers  24  and  26 , acts as a viewing surface and forms a hermetically sealed package between the viewing screen  22  and the baseplate  21 . The viewing screen  22  may be formed from glass. The transparent conductive layer  24  may be formed from indium tin oxide. The cathodoluminescent layer  26  may be segmented into pixels yielding different colors to provide a color display  10 . Materials useful as cathodoluminescent materials in the cathodoluminescent layer  26  include Y 2 O 3 :Eu (red, phosphor P-56), Y 3 (Al, Ga) 5 O 12 :Tb (green, phosphor P-53) and Y 2 (SiO 5 ):Ce (blue, phosphor P-47) available from Osram Sylvania of Towanda PA or from Nichia of Japan.  
           [0003]    The baseplate  21  includes emitters  30  formed on a surface of a substrate  32 . The substrate  32  is coated with a dielectric layer  34  that is formed, in accordance with the prior art, by deposition of silicon dioxide via a conventional TEOS process. The dielectric layer  34  is formed to have a thickness that is approximately equal to or just less than a height of the emitters  30 . This thickness may be on the order of 0.4 microns, although greater or lesser thicknesses may be employed. A conductive extraction grid  38  is formed on the dielectric layer  34 . The extraction grid  38  may be, for example, a thin layer of polycrystalline silicon. An opening  40  is created in the extraction grid  38  having a radius that is also approximately the separation of the extraction grid  38  from the tip of the emitter  30 . The radius of the opening  40  may be about 0.4 microns, although larger or smaller openings  40  may also be employed.  
           [0004]    In operation, signals coupled to the emitter  30  allow electrons to flow to the emitter  30 . Intense electrical fields between the emitter  30  and the extraction grid  38  then cause field emission of electrons from the emitter  30 . A positive voltage, ranging up to as much as 5,000 volts or more. but generally 2,500 volts or less, is applied to the faceplate  20  via the transparent conductive layer  24 . The electrons emitted from the emitter  30  are accelerated to the faceplate  20  by this voltage and strike the cathodoluminescent layer  26 . This causes light emission in selected areas known as pixels, i.e., those areas adjacent to the emitters  30 , and forms luminous images such as text, pictures and the like.  
           [0005]    [0005]FIG. 2 is a simplified plan view showing rows  42  and columns  44  of the emitters  30  and the openings  40  of FIG. 1, according to the prior art. The columns  44  are divided into top columns  44   a  and bottom columns  44   b , as may be seen in FIG. 2. Top  46   a  and bottom  46   b  column driving circuitry is coupled to the top  44   a  and bottom  44   b  columns, respectively. A row driving circuit  48  is coupled to odd rows  42   a  and even rows  42   b . The rows  42  are ormed from strips of the extraction grid  38  that are electrically isolated from ach other. The columns  44   a  and  44   b  are formed from conductive strips that are lectrically isolated from each other and that electrically interconnect groups of he emitters  30 .  
           [0006]    By biasing a selected one of the rows  42  to an appropriate voltage nd also biasing a selected one of the columns  44  to a voltage that is about forty o eighty volts more negative than the voltage applied to the selected row  42 , the itter or emitters  30  located at an intersection of the selected row  42  and olumn  44  are addressed. The addressed emitter or emitters  30  then emit electrons that travel to the faceplate  20 , as described above with respect to FIG. 1.  
           [0007]    Conventional circuitry for driving emitters  30  in field emission displays  10  enables each column  44  once per row address interval and disables each column  44  once per row address interval. The columns  44  present a capacitive load C. Charging and discharging of the capacitance C consumes power in proportion to fCV 2 , where f represents the frequency of charging and discharging the column  44  and V represents the voltage to which the columns  44  are charged. Charging and discharging of the columns  44  in order to drive the emitters  30  forms a major component of the electrical power consumed by the display  10 . As a result, reducing the frequency f, the capacitance C or the voltage V can significantly reduce the electrical power required to operate the display  10 . Displays  10  requiring less electrical power are currently in demand.  
           [0008]    There is therefore need for techniques and apparatus that reduce the amount of electrical power required in order to operate field emission displays.  
         SUMMARY OF THE INVENTION  
         [0009]    In one aspect, the present invention includes a field emission display having a substrate and a plurality of emitters formed on the substrate. Each of the emitters is formed on one of a plurality of emitter conductors that is also a row or a column of the display. The display also includes a porous dielectric layer formed on the substrate and the columns. The porous dielectric layer has an opening formed about each of the emitters and has a thickness substantially equal to a height of the emitters above the substrate. The porous dielectric layer is preferably formed by oxidation of porous polycrystalline silicon. The display further includes an extraction grid formed substantially in a plane defined by respective tips of the plurality of emitters. The extraction grid has an opening surrounding each tip of a respective one of the emitters. The display additionally includes a cathodoluminescent-coated faceplate having a planar surface formed parallel to and near the plane of tips of the plurality of emitters.  
           [0010]    The porous dielectric results in the emitter conductors having reduced capacitance C compared to prior art dielectric layers. Charging and discharging of the emitter conductors in order to drive the emitters forms a major component of the electrical power consumed by the display. By reducing the capacitance of the emitter conductors, the display is able to form luminous images, such as text and the like, while dissipating reduced electrical power.  
           [0011]    In another aspect of the present invention, tips of the emitters are formed from a material having a work function less than four electron volts. The voltage needed in order to drive the emitters, and hence the voltage used to charge and discharge the columns, is proportional to a turn-on voltage for the emitters. Emitters having reduced turn-on voltage draw less electrical power. As a result, baseplates with emitters having low work finction tips are able to form luminous images while dissipating reduced electrical power compared to conventional displays. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a simplified side cross-sectional view of a portion of a display including a faceplate and a baseplate, in accordance with the prior art.  
         [0013]    [0013]FIG. 2 is a simplified plan view showing rows and columns of the emitters of FIG. 1, in accordance with the prior art.  
         [0014]    [0014]FIG. 3 is a simplified flowchart of a process for forming a dielectric having a reduced relative dielectric constant ε R , in accordance with embodiments of the present invention.  
         [0015]    [0015]FIG. 4 is a simplified side view of an emitter having a body formed of high resistivity material and a tip formed of a low work function material, in accordance with embodiments of the present invention.  
         [0016]    [0016]FIG. 5 is a simplified flowchart of a process for forming emitters having reduced work function and integral ballast resistors, in accordance with embodiments of the present invention.  
         [0017]    [0017]FIGS. 6A-6G show the baseplate at various stages in the process of emitter formation, in accordance with embodiments of the present invention.  
         [0018]    [0018]FIG. 7 is a simplified block diagram of a computer including a field emission display, in accordance with embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    [0019]FIG. 3 is a simplified flowchart of a process  75  for forming a dielectric layer  34 ′ (not shown in FIG. 3) having a reduced relative dielectric constant ε R , relative to the prior art, in accordance with embodiments of the present invention. The process  75  begins with a step  77  of forming emitter conductors defining columns  44  (FIG. 2) on the substrate  32  (FIG. 1). In a step  79 , a silicon layer (not shown) is formed on the substrate  32  and on the emitter conductors/columns  44  by conventional processes. In one embodiment, the step  79  includes forming the silicon layer by conventional deposition of polysilicon.  
         [0020]    In a step  81 , the silicon layer is made porous. In one embodiment, the step  81  includes forming voids or pores (not shown) in an n-type silicon layer by a process similar to that described in “Formation Mechanism of Porous Silicon Layers Obtained by Anodization of Monocrystalline n-type Silicon in HF Solutions” by V. Dubin, Surface Science 274 (1992), pp. 82-92. In one embodiment, a current density of between 5 and 40 mA/cm 2  is employed together with 12-24% HF. In general, increasing N D  (silicon donor concentration), HF concentration or anodization current density provides larger pores.  
         [0021]    In another embodiment, the step  81  includes forming voids or pores n a p-type silicon layer by a process similar to that described in “On the orphology of Porous Silicon Layers Obtained by Electrochemical Method” by G. Graciun et al., International Semiconductor Conference CAS &#39;95 Proceedings (IEEE Catalog No. 95TH8071) (1995), pp. 331-334. In one embodiment, a current density of between 1.5 and 30 mA/cm 2  is employed together with either 36 weight % HF-ethanol 1:1 or 49 weight % HF-ethanol 1:3.  
         [0022]    In one embodiment, the silicon layer is anodized or etched until a porosity of greater than 50% is achieved, i.e., more than one-half of the volume of the silicon layer is converted to pores or voids. In another embodiment, the silicon layer is anodized or etched until a porosity of greater than 75% is achieved.  
         [0023]    In a step  83 , the porous silicon layer is oxidized. In one embodiment, the oxidation of the step  83  is carried out by conventional thermal oxidation at a temperature in excess of 950 to 1,000° C. In another embodiment, an inductively-coupled oxygen-argon mixed plasma is employed for oxidizing the silicon layer, as described in “Low-Temperature Si Oxidation Using Inductively Coupled Oxygen-Argon Mixed Plasma” by M. Tabakomori et al., Jap. Jour. Appl. Phys., Part 1, Vol. 36, No. 9A (September 1997), pp. 5409-5415. In yet other embodiments, electron cyclotron resonance nitrous oxide plasma is employed for oxidizing the silicon, as described in “Oxidation of Silicon Using Electron Cyclotron Resonance Nitrous Oxide Plasma and its Application to Polycrystalline Silicon Thin Film Transistors”, J. Lee et al., Jour. Electrochem. Soc., Vol. 144, No. 9 (September 1997), pp. 3283-3287 and “Highly Reliable Polysilicon Oxide Grown by Electron Cyclotron Resonance Nitrous Oxide Plasma” by N. Lee et al., IEEE E1. Dev. Lett., Vol. 18, No. 10 (October 1997), pp. 486-488. Plasma oxidation allows the temperature of the baseplate  21  (FIG. 1) to be as low as 450-500° C. during the step  83 .  
         [0024]    Oxidation of the porous silicon layer results in the porous silicon dioxide layer  34 ′ (not shown in FIG. 3), having a porosity that is related to that of the porous silicon layer. One volume of silicon oxidizes to provide approximately 1.55 volumes of silicon dioxide. Accordingly, a silicon layer having 50% voids will, after complete oxidation, result in the porous silicon dioxide layer  34 ′ having approximately 22.5% voids (ignoring any expansion of the porous silicon dioxide layer  34 ′ in the vertical direction during oxidation). Similarly, a silicon layer having 75% voids will, after complete oxidation, result in the porous silicon dioxide layer  34 ′ having approximately 61.5% voids. Either of these examples will result in the porous silicon dioxide layer  34 ′ having a relative dielectric constant ε R  that is substantially reduced compared to a dielectric layer  34  formed from silicon dioxide incorporating no voids (ε R ≅3.9).  
         [0025]    In one embodiment, a relative dielectric constant ε R  of less than 3 is provided, corresponding to a void content of about 25% in the porous silicon dioxide layer  34 ′. In another embodiment, a relative dielectric constant ε R  of less than 1.6 is provided, corresponding to a void content of about 60% in the porous silicon dioxide layer  34 ′. In some embodiments, the porous silicon dioxide layer  34 ′ forms a series of columnar spacers.  
         [0026]    In an optional step  85 , the porous silicon dioxide layer  34 ′ is planarized. The step  85  may include conventional chemical-mechanical polishing, or may include formation of a layer of dielectric material having planarizing properties (e.g., conventional TEOS deposition). In a step  87 , the extraction grid  38  is formed on the porous silicon dioxide layer  34 ′ using conventional techniques and is etched to provide the rows  42  (FIG. 2). Although the field emission display is described as having emitters arranged in columns and the extraction grid arranged in rows, it will be understood that the emitters alternatively may form rows and the extraction grid may form columns. The process  75  then ends.  
         [0027]    [0027]FIG. 4 is a simplified side view of an emitter  30 ′ having an emitter body  30 A formed of high resistivity material and an emitter tip  30 B formed of a low work function material, in accordance with embodiments of the present invention. The emitter body  30 A is formed on one of the columns  44  of FIG. 2. Advantages to forming the emitter body  30 A from a high resistivity material include current limiting, and equalizing the current drawn by the emitters  30 ′ despite the emitters  30 ′ having different turn-on voltages. Current limiting also obviates catastrophic failure of the display  10  (FIG. 1) in the event that one or more emitters  30 ′ become short-circuited to the extraction grid  38 . In one embodiment, resistance values for the emitter body  30 A may fall into the range of 4 MΩ to 40 MΩ for conventional drive voltages V and may be less if the turn-on voltage for the emitter  30 ′ is reduced. In one embodiment, the emitters  30 ′ have emitter bodies  30 A formed from material having a resistivity ρ of ca. 10 2 -10 3  Ω-cm and emitter tips  30 B formed from materials having a work function φ or electron affinity χ of less than four eV, or even three eV or less.  
         [0028]    Advantages to forming emitters  30 ′ to have tips  30 B formed from a metal having a low work function φ, or a semiconductor having a low electron affinity χ, include reduced turn-on voltage for the emitter  30 ′. As a result, the emitters  30 ′ do not require as large a voltage V in order to be able to bombard the faceplate  20  with sufficient electrons to form the desired images. Power consumption for the display  10  is then reduced.  
         [0029]    Representative values for work functions φ or electron affinities χ for several materials are summarized below in Table I. Measured or achieved work functions φ/electron affinities χ depend strongly on surface treatment and surface contamination and may vary from the values given in Table I.  
                             TABLE I                           Metal work functions φ and semiconductor       electron affinities χ for selected materials.                φ or χ (eV)   Material                       4.3   W           4.05*   Si (χ)           3.6/3.7*   SiC (χ)           3.6   Zr           3.3   La           3-3.3   Zn           2.9   TiN           2.8   LaB 6             2.6   Ce           1.8-2.2   Ba           1.4**   C (diamond, χ)           0.9-4.05   Silicon oxycarbide (projected, χ)                                              
 
         [0030]    [0030]FIG. 5 is a simplified flowchart of a process  100  for forming the emitters  30 ′ of FIG. 4, in accordance with embodiments of the present invention. FIGS. 6A-6G show the baseplate  21  at various stages in the formation of the emitters  30  or  30 ′, in accordance with embodiments of the present invention. In one embodiment, the process  100  results in emitters  30 ′ having tips  30 B providing reduced work function φ and emitter bodies  30 A providing integral ballast resistors. In another embodiment, the process  100  results in emitters  30  that are formed after the porous silicon dioxide layer  34  is formed.  
         [0031]    [0031]FIG. 6A shows a conductor  90  forming the columns  44  (FIG. 2), the dielectric layer  34  or the porous silicon dioxide layer  34 ′ and the extraction grid  38 , which were previously formed on the substrate  32 . The process  100  begins with a step  102  of forming the openings  40  in the extraction  35  grid  38  (FIG. 6B). The openings  40  may be formed by conventional lithography and etching. In a step  104 , the dielectric layer  34  or  34 ′ is etched to expose the conductor  90  (FIG. 6C). The step  104  may use conventional wet chemical etching (e.g., etching using buffered oxide etch, a standard HF solution) to provide a curved edge profile, shown as a solid trace in FIG. 6C, or may use reactive ion etching to provide a vertical edge profile, shown as a dashed trace in FIG. 6C.  
         [0032]    In a step  106 , a sacrificial layer  107  (FIG. 6D) is formed. The sacrificial layer  107  is formed on the extraction grid  38  but not on the conductor  90 . In one embodiment, the sacrificial layer  107  is formed by evaporation of, e.g., nickel, from a point source such as an electron beam evaporator, so that the nickel atoms approach the extraction grid  38  at an angle of ca. 75° or more from a normal (see direction arrow  107 ′) to the extraction grid  38 , causing interiors of the openings  40  to be shadowed from the incoming nickel atoms. The baseplate  21  is rotated about the normal  107 ′ to the extraction grid  38  during this evaporation to provide uniform coverage of the extraction grid  38  by the sacrificial layer  107 .  
         [0033]    In a step  108 , the emitter body  30 A is formed of high resistivity material (FIG. 6E) by deposition of a layer  109 . In one embodiment, the emitter body  30 A forms the bottom two-thirds of the overall height of the emitter  30 ′.  
         [0034]    In one embodiment, the emitter body  30 A is formed by coevaporation of SiO together with Mn to provide the layer  109  and the emitter body  30 A having 7-10 atomic percent Mn, as described in “Conduction Mechanisms In Co-Evaporated Mixed Mn/SiO x  Thin Films” by S. Z. A. Zaidi, Jour. of Mater. Sci. 32, (1997), pp. 3349-3353. Other embodiments may employ SiO formed as described in “Production of SiO 2  Films Over Large Substrate Area by Ion-Assisted Deposition of SiO With a Cold Cathode Source” by I. C. Stevenson, Soc. of Vac. Coaters, Proc. 36 TH  Annual Tech. Conf. (1993), pp. 88-93 or “Improvement of the ITO-P Interface in α-Si:H Solar Cells using a Thin SiO Intermediate Layer” by C. Nunes de Carvalho et al., Proc. MRS Spring Symposium, Vol. 420 (1996), pp. 861-865, together with a co-deposited metal. Other metals (e.g., Cr, Au, Cu etc.) may be used to form cermet or cermet-like materials as described by Zaidi et al.  
         [0035]    In a step  110 , the emitter tips  30 B are formed (FIG. 6F) by deposition of a layer  111 . In one embodiment, the layer  111  and the emitter tips  30 B are formed by evaporation of one of the materials listed in Table I that are amenable to deposition by vacuum evaporation. TiN may be formed in situ by evaporation of a thin Ti film (e.g., two hundred Angstroms or more) followed by rapid thermal annealing in a nitrogen-bearing atmosphere (e.g., ammonia). In other embodiments, other materials may be sputtered or may be deposited by chemical vapor deposition.  
         [0036]    In one embodiment, silicon oxycarbide is employed as the emitter tips  30 B in the step  110 . A process for forming thin microcrystalline films of silicon oxycarbide is described in “Transport Properties of Doped Silicon Oxycarbide Microcrystalline Films Produced by Spatial Separation Techniques” by R. Martins et al., Solar Energy Materials and Solar Cells 41/42 (1996), pp. 493-517. A diluent/reaction gas (e.g., hydrogen) is introduced directly into a region where plasma ignition takes place. The mixed gases containing the species to be deposited are introduced close to the region where the growth process takes place, often a substrate heater. A bias grid is located between the plasma ignition and the growth regions, spatially separating the plasma and growth regions.  
         [0037]    Deposition parameters for producing doped microcrystalline Si x :C y :O z :H films may be defined by determining the hydrogen dilution rate and power density that lead to microcrystallization of the grown film. The power density is typically less than 150 milliwatts per cm 3  for hydrogen dilution rates of 90% +, when the substrate temperature is about 250° C. and the gas flow is about 150 sccm. The composition of the films may then be varied by changing the partial pressure of oxygen during film growth to provide the desired characteristics.  
         [0038]    In one embodiment, SIC is employed as the emitter tips  30 B in the step  110 . SiC films may be fabricated by chemical vapor deposition, sputtering, laser ablation, evaporation, molecular beam epitaxy or ion implantation of carbon into silicon. Vacuum annealing of silicon substrates is a method that may be used to provide SiC layers having thicknesses ranging from 20 to 30 nanometers, as described in “Localized Epitaxial Growth of Hexagonal and Cubic SiC Films on Si by Vacuum Annealing” by Luo et al., Appl. Phys. Lett. 69(7), (1996), pp. 916-918. This embodiment requires that the emitter tip  30 B either be formed from or be coated with silicon. Prior to vacuum annealing, the emitters  30 ′ are degreased with acetone and isopropyl alcohol in an ultrasonic bath for fifteen minutes, followed by cleaning in a solution of H 2 SO 4 :H 2 O 2  (3:1) for fifteen minutes. A five minute rinse in deionized water then precedes etching with a 5% HF solution. The emitters  30 ′ are blown dry using dry nitrogen and placed in the vacuum chamber and the chamber is pumped to a base pressure of 1-2×10 −6  Torr. The substrate is heated to 750 to 800° C. for half an hour to grow the microcrystalline SiC film.  
         [0039]    In some embodiments, silicon is employed as the emitter tips  30 B in the step  110 . Methods for depositing high quality polycrystalline films of silicon on silicon dioxide substrates are given in “Growth of Polycrystalline Silicon at low Temperature on Hydrogenated Microcrystalline Silicon (μc-Si:H) Seed Layer” by Parks et al., Proceedings of the 1997 MRS Spring Symposium, Vol. 467 (1997), pp. 403-408, “Novel Plasma Control Method in PECVD for Preparing Microcrystalline Silicon” by Nishimiya et al., Proceedings of the 1997 MRS Spring Symposium, Vol. 467 (1997), pp. 397-401 and “Low Temperature (450° C.) Poly-Si Thin Film Deposition on SiO 2  and Glass Using a Microcrystalline-Si Seed Layer” by D. M. Wolfe et al., Proceedings of the 1997 MRS Spring Symposium, Vol. 472 (1997), pp. 427-432. A process providing grain sizes of about 4 nm is described in “Amorphous and Microcrystalline Silicon Deposited by Low-Power Electron-Cyclotron Resonance Plasma-Enhanced Chemical-Vapor Deposition” by J. P. Conde et al., Jap. Jour. Appl. Phys., Part I, Vol. 36, No. 1A (June 1997), pp. 38-49. Deposition conditions favoring small grain sizes for microcrystalline silicon include high hydrogen dilution, low temperature, low deposition pressure and low source-to-substrate separation.  
         [0040]    Following the step  110 , the sacrificial layer  107  is removed, along with those portions of the layers  109  and  111  that do not form parts of the emitters  30 ′, in a step  112 . In one embodiment, a nickel sacrificial layer  107  is removed using electrochemical etching of the nickel. Other conventional approaches for forming and later removing sacrificial layers  107  may also be used when they are compatible with the processes of the steps  106 - 112 . The process  100  then ends and further processing is carried out using conventional fabrication techniques.  
         [0041]    In one embodiment, emitters  30  formed from a single material are provided together with the porous silicon dioxide layer  34 ′ formed as described in conjunction with FIG. 3 by performing the steps  102 - 106 , performing a step  110 ′ (not illustrated) of depositing a single material and then performing step  112 . In this embodiment, the advantages of the porous silicon dioxide layer  34 ′ may be provided together with conventional emitters  30 .  
         [0042]    It will be appreciated that the porous silicon dioxide layer  34 ′ may be formed after formation of the emitters  30 . In these embodiments, the emitters  30  may be conventionally formed before or after the step  77  of FIG. 3. The steps  79 - 87  may, in some embodiments, follow the formation of the emitters  30  or  30 ′. In these embodiments, conventional chemical-mechanical polishing followed by etching of the porous silicon dioxide layer  34 ′ results in a baseplate  21  (FIG. 1) useful in field emission displays  10 .  
         [0043]    [0043]FIG. 7 is a simplified block diagram of a portion of a computer  120  including the field emission display  10 , in accordance with the invention as described with reference to FIGS. 3-6 and associated text. The computer  120  includes a central processing unit  122  coupled via a bus  124  to a memory  126 , function circuitry  128 , a user input interface  130  and the field emission display  10 , according to embodiments of the present invention. The memory  126  may or may not include a memory management module (not illustrated) and does include ROM for storing instructions providing an operating system and a read-write memory for temporary storage of data. The processor  122  operates on data from the memory  126  in response to input data from the user input interface  130  and displays results on the field emission display  10 . The processor  122  also stores data in the read-write portion of the memory  126 . Examples of systems where the computer  120  finds application include personal/portable computers, camcorders, televisions, automobile electronic systems, microwave ovens and other home and industrial appliances.  
         [0044]    Field emission displays  10  for such applications provide significant advantages over other types of displays, including reduced power consumption, improved range of viewing angles, better performance over a wider range of ambient lighting conditions and temperatures and higher speed with which the display can respond. Field emission displays find application in most devices where, for example, liquid crystal displays find application.  
         [0045]    Although the present invention has been described with reference to a preferred embodiment, the invention is not limited to this preferred embodiment. Rather, the invention is limited only by the appended claims, which include within their scope all equivalent devices or methods which operate according to the principles of the invention as described.