Micro power switch using a cold cathode and a driving method thereof

• US 6,057,636 A
• Filed: 09/16/1997
• Issued: 05/02/2000
• Est. Priority Date: 09/17/1996
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Nakayama, Kazuya, Ohashi, Hiromichi, Sakuma, Naoshi, Sakai, Tadashi, Ono, Tomio
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): HAYNES, MACK NELSON
• Application Number:
  US08/931,417
• Time in Patent Office: 959 Days
• Field of Search: 313/309-11, 313/351, 313/336, 313/346 R, 313/495-97, 313/306, 313/307, 313/308, 345/55, 345/74-75, 345/80
• US Class Current: 313/306
• CPC Class Codes: H01J 21/105 with microengineered cathode and control electrodes, e.g. Spindt-type
• CPC Class Codes: H03K 17/545 using microengineered devices, e.g. field emission devices

Abstract

The present invention provides a micro power switch comprising a cold cathode for emitting electrons, an anode for capturing the electrons emitted from the cold cathode, and a control electrode for controlling an amount of the electrons emitted from the cold cathode, wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode, the anode is applied with a positive potential in relation to the cold cathode, and the control electrode is applied with a potential equal to or lower than a potential of the cold cathode.

Claims

1. A micro power switch comprising:

a cold cathode for emitting electrons;

an anode for capturing the electrons emitted from the cold cathode, the anode being opposed to the cold cathode; and

a control electrode, provided near the cold cathode, for controlling an amount of the electrons emitted from the cold cathode,

wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode, the anode is applied with a positive potential with respect to the cold cathode, and the control electrode is applied with a varying potential equal to or lower than a potential of the cold cathode; and

wherein in the case where the electron emission from the cold cathode is stopped, the varying potential is lower than the potential of the cold cathode.

2. The micro power switch according to claim 1, wherein the control electrode is made of Si, and the cold cathode is made of one of carbon-based material having an SP³ bond, amorphous carbon, carbon-nano tube, GaN, BN, and material containing any of carbon-based material having an SP³ bond, amorphous carbon, carbon-nano tube, GaN, and BN.

3. The micro power switch according to claim 1, wherein at least a part of a surface of the control electrode is covered with one of platinum, chrome, tungsten, niobium, and tungsten-carbide.

4. The micro power switch according to claim 1, wherein at least a part of a surface of the control electrode is covered with an insulating layer as a barrier for preventing electrons from being emitted.

5. The micro power switch according to claim 1, further comprising an insulating layer provided between the anode and the control electrode,

wherein a distance between a top of the cold cathode and the anode is shorter than a length of the insulating layer.

6. The micro power switch according to claim 4, wherein the insulating layer is one of Al₂ O₃, MgF₂, SiO₂, and TiO₂.

7. The micro power switch according to claim 1, further comprising an inducing electrode provided between the control electrode and the anode and applied with a positive potential in relation to the cold cathode.

8. The micro power switch according to claim 7, wherein the inducing electrode is formed like a grid.

9. The micro power switch according to claim 5, further comprising an inducing electrode provided between the control electrode and the anode and applied with a positive potential in relation to the cold cathode.

10. The micro power switch according to claim 9, wherein the inducing electrode is formed like a grid.

11. The micro power switch according to claim 7, further comprising an intermediate electrode provided between the inducing electrode and the anode and applied with a positive potential in relation to the anode.

12. The micro power switch according to claim 9, further comprising an intermediate electrode provided between the inducing electrode and the anode and applied with a positive potential in relation to the anode.

13. The micro power switch according to claim 1, wherein the anode is made of Mo.

14. The micro power switch according to claim 1, wherein the cold cathode is formed by a transfer mold method.

15. The micro power switch according to claim 1, wherein a potential between the anode and the cold cathode when the micro power switch is rendered electrically conductive is 1/2 or less of a potential between the anode and the cold cathode when the micro power switch is shut off.

16. A driving method for a micro power switch comprising as cold cathode for emitting electrons, an anode for capturing the electrons emitted from the cold cathode, the anode being opposed to the cold cathode;

a control electrode, provided near the cold cathode, for controlling an amount of the electrons emitted from the cold cathode, wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode, the anode is applied with a positive potential with respect to the cold cathode, comprising steps of;

applying, to the anode, a potential necessary for drawing the electrons from the cold cathode; and

applying, to the control electrode, a varying potential equal to or lower than a potential of the cold cathode;

wherein in order to prevent the electrons from being emitted from the cold cathode, the varying potential is lower than the potential of the cold cathode.

17. A driving method for a micro power switch comprising as cold cathode for emitting electrons, an anode for capturing the electrons emitted from the cold cathode, the anode being opposed to the cold cathode;

a control electrode, provided near the cold cathode, for controlling an amount of the electrons emitted from the cold cathode, and an insulating layer provided between the anode and the control electrode, wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode, and a distance between a top of the cold cathode and the anode is shorter than a length of the insulating layer, comprising steps of;

applying, to the anode, a potential necessary for drawing the electrons from the cold cathode; and

applying, to the control electrode, a varying potential equal to or lower than a potential of the cold cathode;

wherein in order to prevent the electrons from being emitted from the cold cathode, the varying potential is lower than the potential of the cold cathode.

18. A driving method for a micro power switch comprising as cold cathode for emitting electrons, an anode for capturing the electrons emitted from the cold cathode, the anode being opposed to the cold cathode;

a control electrode, provided near the cold cathode, for controlling an amount of the electrons emitted from the cold cathode, an inducing electrode provided between the control electrode and the anode and applied with a positive potential in relation to the cold cathode, and an intermediate electrode provided between the inducing electrode and the anode and applied with a positive potential in relation to the anode, wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode, comprising steps of;

applying, to the anode, a potential necessary for drawing the electrons from the cold cathode; and

applying, to the control electrode, a varying potential equal to or lower than a potential of the cold cathode;

wherein in order to prevent the electrons from being emitted from the cold cathode, the varying potential is lower than the potential of the cold cathode.

19. A micro power switch comprising:

a cold cathode for emitting electrons;

an anode for capturing the electrons emitted from the cold cathode, the anode being opposed to the cold cathode; and

a control electrode, provided near the cold cathode, for controlling an amount of the electrons emitted from the cold cathode,

wherein the control electrode is applied with a varying potential equal to or lower than a potential of the cold cathode; and

wherein in the case where the micro power switch is in an off state the varying potential is lower than the potential of the cold cathode.

20. The micro power switch according to claim 19, wherein the control electrode is applied with a potential lower than a zero potential in case where the micro power switch is in the off state.

21. The micro power switch according to claim 19, wherein the control electrode is non-biased in case where the micro power switch is in an on state.

22. The micro power switch according to claim 19, wherein the cold cathode is made of one of carbon-based material having an SP³ bond, amorphous carbon, carbon-nano tube, GaN, BN, and material containing any of carbon-based material having an SP³ bond, amorphous carbon, carbon-nano tube, GaN, and BN.

23. The micro power switch according to claim 19, wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode.

24. The micro power switch according to claim 19, wherein a potential between the anode and the cold cathode when the micro power switch is on state is 1/2 or less of a potential between the anode and the cold cathode when the micro power switch is in the off state.

25. A micro power switch comprising:

a cold cathode for emitting electrons;

an anode for capturing the electrons emitted from the cold cathode, the anode being opposed to the cold cathode; and

a control electrode, provided near the cold cathode, for controlling an amount of the electrons emitted from the cold cathode,

wherein the control electrode is applied with a varying potential equal to or lower than a potential of the cold cathode;

in the case where the micro power switch is in an off state, the varying potential is lower than the potential of the cold cathode; and

the cold cathode is made of one of carbon-based material having an SP³ bond, amorphous carbon, carbon-nano tube, GaN, BN, and material containing any of a carbon-based material having an SP³ bond, amorphous carbon, carbon-nano tube, GaN, BN.

26. The micro power switch according to claim 25, wherein the control electrode is non-biased in case where the micro power switch is in an on state.

27. The micro power switch according to claim 25, wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode.

28. The micro power switch according to claim 25, wherein a potential between the anode and the cold cathode when the micro power switch is on state is 1/2 or less of a potential between the anode and the cold cathode when the micro power switch is in the off state.

29. The micro power switch according to claim 26, wherein the cold cathode is made of material having a smaller electron emission barrier than the control electrode.

30. The micro power switch according to claim 26, wherein a potential between the anode and the cold cathode when the micro power switch is on state is 1/2 or less of a potential between the anode and the cold cathode when the micro power switch is in the off state.