Field emission device

• US 4,663,559 A
• Filed: 11/15/1985
• Issued: 05/05/1987
• Est. Priority Date: 09/17/1982
• Status: Expired due to Term

• Current Assignee: Alton O. Christensen
• Original Assignee: Alton O. Christensen
• Inventors: Christensen, Alton O.
• Primary Examiner(s): Chatmon, Saxfield
• Application Number:
  US06/798,587
• Time in Patent Office: 536 Days
• Field of Search: 313/336, 313/346, 313/310, 313/311, 313/331-335, 313/633, 419/10, 419/19, 75/230, 75/232, 75/235
• US Class Current: 313/336
• CPC Class Codes: H01J 1/3042 microengineered, e.g. Spindt-type
• CPC Class Codes: H01J 2201/30403 characterised by the emitter shape
• CPC Class Codes: H01J 2201/319 Circuit elements associated with the emitters by direct integration
• CPC Class Codes: H01J 3/021 Electron guns using a field emission, photo emission, or secondary emission electron source

Abstract

A device is disclosed which produces high current, low noise, low lateral energy, stochastic electron emission from a multiplicity of insulative particles subjected to a field. The insulative particles are in and of a surface thickness comprised of a random mixture of insulative and conductive particles in ohmic contact. Emission is achieved at applied potentials of about 5 volts which produce a field sufficient to emit electron currents of nanoamperes to milliamperes. Single devices or arrays of devices may be batch fabricated. Each device has an imtegral, implicity self-aligned electron optic system comprising means for modulating, focusing and deflecting the formed current beam, and means shielding the device from ambient magnetic fields.

Claims

1. A field emission device wherein emission is obtained from particles of insulative material under the influence of a field, and wherein a barrier to emission is the conduction band width and is less than about 1 ev, and wherein the insulative particles are a component of a cermet of randomly arranged conductive and insulative particles, and ohmic contact exists between the particles.

2. The device of claim 1 wherein the insulative particles have an average diameter of about 3.5 nanometers.

3. The device of claim 1 wherein electrons in the insulative particles have at least the energy of the Fermi level of the conductive material, and energy imparted by an applied field to the electrons initiates emission.

4. The device of claim 3 wherein said field is sufficient to cause electron traps in said insulative particles to be overfilled, and all electrons flow in the insulative material conduction band.

5. The field emission device of claim 3 wherein said cermet comprises randomly arranged conductive particles conductively connected to randomly arranged insulative particles.

6. The field emission device of claim 4 wherein said cermet is formed upon a conductive substrate, and a separate conductor is spaced above and insulated from said substrate and said cermet, and a field is formed by a potential applied between said substrate and said separate conductor.

7. The field emission device of claim 3 wherein the cermet is formed into pointed structure and wherein the particles at the surface of the point are insulative particles.

8. The field emission device of claim 7 wherein said pointed structure is centered in an aperture of a conductive electrode, and said cermet is formed upon and conductively connected at a base to a conductive substrate and a potential applied between said substrate and conductive electrode operates on said point and said cermet to emit electron flow from said point.

9. The field emission device of claim 1 wherein the conductive material is refactory metal, nickel, silver, aluminum, rare earth borides, highly doped silicon or a silicide of refractory metal and having a lesser work function that that of said insulative material.

10. The field emission device of claim 1 wherein the insulative particles and the conductive particles have a maximum dimension of about 5.0 nanometers.

11. The field emission device of claim 1 wherein the radius conductive particles are trichromium silicide.

12. The device of claim 1 wherein the insulative material is Al₂ O₃, BeO, B₂ O₃, BN, CaO, MgO, SiO₂ or Si₃ N₄.

13. The device of claim 12 wherein the insulative material has minimal affinity for oxygen or other gasses of the same electropolarity prohibiting chemisorption on the emitting particles which would otherwise cause noise or degradation of emission.

14. The field emission device of claim 6 wherein said potential is less than the ionization potential of gasses or vapors residual within or diffusing within said field preventing abalation by ionized particles of said point and resulting noise modulation of emission and degradation of emission levels.

24. The field emission device of claim 1 formed of trichromium silicide particles in ohmic contact with silica or beryllia particles.

15. A field emission device comprising a conductive substrate conductively connected to cermet of insulative and conductive particles of pyramidal or conical shape with a point centered in an aperture of a first conductor, and a potential is applied between said substrate and said first conductor forming a field causing electrons to flow through the cermet in the conduction band of the insulative particles with a barrier to emission of less than about 1 ev, the electron flow to the point of the cermet into vacuum being from insulative particles of the surface of the point, the potential producing the field for emission being less than the ionization potential of gasses or vapors residual within or diffusing within the field to preserve the integrity of the emitting insulative particles, reduce noise and emitted current degradation, and allow operation in the presence of vapors or gasses in the field.

16. The field emission device of claim 15 including two pairs of deflection bars orthogonal to and insulated from each other and from said first conductor, and said bars are centered relative to the emitting point;

voltage means applied to one deflection pair;

separate voltage means connected to the other deflection pair; and

wherein said deflection bars are operative to deflect the emitted electrons and to focus the emitted electrons.

17. The field emission device of claim 16 wherein the spacing between the deflection bar pairs is less than 1.7 micrometer.

18. The field emission device of claim 16 wherein the voltage applied by said voltage means is less than the ionization potential of gasses or vapors.

19. A multiplicity of the field emission devices of claim 15 sharing a common substrate each directed to an assigned area of respective targets, and including integrated circuit control means integrally supported by said common substrate for the multiplicity of field emission devices.

20. The field emission devices of claim 19 wherein said integrated circuit means operates individual field emitters modulating and deflecting electron emission therefrom.

21. The field emission device of claim 16, wherein the deflection voltages supplied to the orthogonal deflection bars are controllably offset from a reference potential to focus the electron beam.

22. The field emission device of claim 15 wherein the emitting surface is multiplicity of insulative particles within a 60°

solid angle point and said multiplicity of insulative particles simultaneously emit electrons.

23. The field emission device of claim 15 formed of trichromium silicide particles in ohmic contact with silica or beryllia particles.