Energetic-electron emitters

• US 5,729,094 A
• Filed: 04/15/1996
• Issued: 03/17/1998
• Est. Priority Date: 04/15/1996
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Lyszczarz, Theodore M., Geis, Michael W., Twichell, Jonathan C.
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Bettendorf, Justin P.
• Application Number:
  US08/632,026
• Time in Patent Office: 701 Days
• Field of Search: 315/169.1, 315/169.2, 315/169.3, 313/309, 313/310, 313/311, 313/495, 313/496, 313/497, 257/77
• US Class Current: 315/169.1
• CPC Class Codes: H01J 1/304 Field-emissive cathodes

Abstract

An energetic-electron emitter providing electrons having kinetic energies on the order of one thousand electron volts without acceleration through vacuum. An average electric field of 10⁵ V/m to 10¹⁰ V/m applied across a layer of emissive cathode material accelerates electrons inside the layer. The cathode material is a high-dielectric strength, rigid-structure, wide-bandgap semiconductors, especially type Ib diamond. A light-emitting device incorporates the energetic-electron emitter as a source of excitation to luminescence.

Claims

1. An electron-emissive device comprising:

a. a cathode body of diamond, the body having a surface with first and second locations separated by a thickness;

b. first and second conductive materials disposed respectively on the first and second locations; and

c. a voltage source, electrically connected to the cathode body by means of the first and second conductive materials so as to impose a body electric field having a body average amplitude greater than 10⁵ V/m across the thickness, the imposition of the body electric field causing the cathode body to emit electrons having kinetic energies.

2. The device of claim 1 wherein the voltage source imposes a dc electric field.

3. The device of claim 1 wherein the thickness is at least 10 μ

m.

4. The device of claim 1 wherein the thickness is at least 100 μ

m.

5. The device of claim 1 wherein the thickness is on the order of 1 mm.

6. The device of claim 1 wherein the diamond contains substitutional nitrogen.

7. The device of claim 6 wherein the substitutional nitrogen is present at a concentration equal to at least 10¹⁸ cm^-3.

8. The device of claim 1 wherein the diamond is type Ib diamond.

9. The device of claim 1 wherein the diamond is in the form of a film.

10. The device of claim 1 wherein the diamond is a single crystal.

11. The device of claim 1 wherein the first conductive material is disposed on the first location with an interface having a roughness characterized by a radius of curvature less than 15 nm between the cathode body surface and the first conductive material.

12. The device of claim 1 wherein the body average amplitude of the body electric field is greater than 10⁶ V/m.

13. The device of claim 1 wherein the body average amplitude of the body electric field is greater than 10⁷ V/m.

14. The device of claim 1 wherein the body average amplitude of the body electric field is greater than 10⁸ V/m.

15. The device of claim 1 wherein upon emission from the cathode body, electrons have kinetic energies of at least 50 eV.

16. The device of claim 1 wherein upon emission from the cathode body, electrons have kinetic energies of at least 200 eV.

17. The device of claim 1 wherein upon emission from the cathode body, electrons have kinetic energies of at least 500 eV.

18. The device of claim 1 wherein upon emission from the cathode body, electrons have kinetic energies equal to at least 10% of the energy corresponding to completely loss-free acceleration of an electron through the imposed body electric field across the thickness.

19. The device of claim 1 wherein upon emission from the cathode body, electrons have kinetic energies equal to at least 40% of the energy corresponding to completely loss-free acceleration of an electron through the imposed body electric field across the thickness.

20. The device of claim 1 further comprising phosphor material arranged to receive emitted electrons, thereby being excited to emit light.

21. The device of claim 1 further comprising an anode opposing the cathode body across an expanse of vacuum and a second voltage source coupled to the anode so as to impose a vacuum electric field having a vacuum average amplitude across the expanse of vacuum.

22. The device of claim 21 wherein the vacuum average amplitude is smaller than the body average amplitude of the body electric field imposed across the thickness of the cathode body.

23. The device of claim 22 wherein the vacuum electric field accelerates emitted electrons toward the anode, thereby increasing their kinetic energies by an increment, the increment being less than four times the kinetic energies of electrons upon emission from the cathode body.

24. The device of claim 1 wherein the body average amplitude of the body electric field is greater than 10⁹ V/m.

25. The device of claim 1 wherein the average field strength of the electric field is greater than 10¹⁰ V/m.

26. The device of claim 1 wherein the second conductive material is carbonaceous.

27. The device of claim 1 wherein the emitted electrons leave the cathode body at one of the first and the second locations.

28. The device of claim 1 further comprising an emission-enhancing material disposed on the surface, the emitted electrons leaving the cathode body through the emission-enhancing material.

29. The device of claim 1 the second conductive material is graphite.

30. An electron-emissive device comprising:

a. a cathode body of diamond, the body having a surface with first and second locations separated by a thickness;

b. first and second conductive materials disposed respectively on the first and second locations;

c. a phosphor material in intimate contact with the cathode body; and

d. a voltage source, electrically connected to the cathode body by means of the first and second conductive materials so as to impose a body electric field having a body average amplitude greater than 10⁵ V/m across the thickness, the imposition of the body electric field causing electrons having kinetic energies to leave the cathode body and enter the phosphor material.

31. The device of claim 30 wherein the phosphor material is disposed on the second conductive material so that electrons enter the phosphor material directly from the first conductive material, without passing through vacuum.

32. An electron-emissive device comprising:

a. a cathode body of diamond, the body having a thickness;

b. an anode opposing the cathode body across an expanse of vacuum; and

c. a voltage source, coupled to the cathode body and to the anode so as to impose a body electric field, having a body average amplitude greater than 10⁵ V/m, across the thickness and a vacuum electric field, having a vacuum average amplitude smaller than the body average amplitude, across the expanse of vacuum, the imposition of the body electric field causing the cathode body to emit into the vacuum electrons having kinetic energies.

33. The device of claim 32 wherein the voltage source imposes a dc electric field.

34. The device of claim 32 wherein the thickness is at least 10 μ

m.

35. The device of claim 32 wherein the thickness is at least 100 μ

m.

36. The device of claim 32 wherein the thickness is on the order of 1 mm.

37. The device of claim 32 wherein the diamond contains substitutional nitrogen.

38. The device of claim 37 wherein the substitutional nitrogen is present at a concentration equal to at least 10¹⁸ cm^-3.

39. The device of claim 32 wherein the diamond is type Ib diamond.

40. The device of claim 32 wherein the diamond is in the form of a film.

41. The device of claim 32 wherein the diamond is a single crystal.

42. The device of claim 32 wherein the cathode body has a surface and further comprising a conductive material disposed on the surface with an interface having a roughness characterized by a radius of curvature less than 15 nm between the surface and the conductive material, the voltage source electrically contacting the cathode body by means of the conductive material.

43. The device of claim 32 wherein the body average amplitude of the body electric field is greater than 10⁶ V/m.

44. The device of claim 32 wherein the body average amplitude of the body electric field is greater than 10⁷ V/m.

45. The device of claim 32 wherein the body average amplitude of the body electric field is greater than 10⁸ V/m.

46. The device of claim 32 wherein upon emission from the cathode body, electrons have kinetic energies of at least 50 eV.

47. The device of claim 32 wherein upon emission from the cathode body, electrons have kinetic energies of at least 200 eV.

48. The device of claim 32 wherein upon emission from the cathode body, electrons have kinetic energies of at least 500 eV.

49. The device of claim 32 wherein upon emission from the cathode body, electrons have kinetic energies equal to at least 10% of the energy corresponding to completely loss-free acceleration of an electron through the imposed body electric field across the thickness.

50. The device of claim 32 wherein upon emission from the cathode body, electrons have kinetic energies equal to at least 40% of the energy corresponding to completely loss-free acceleration of an electron through the imposed body electric field across the thickness.

51. The device of claim 32 further comprising phosphor material arranged to receive emitted electrons, thereby being excited to emit light.

52. The device of claim 51 wherein the phosphor material is disposed on the anode.

53. The device of claim 32 wherein the vacuum electric field accelerates emitted electrons toward the anode, thereby increasing their kinetic energies by an increment, the increment being less than four times the kinetic energies of electrons upon emission from the cathode body.

54. The device of claim 32 wherein the body average amplitude of the body electric field is greater than 10⁹ V/m.

55. The device of claim 32 wherein the body average amplitude of the body electric field is greater than 10¹⁰ V/m.

56. The device of claim 32 wherein the cathode body has a surface and further comprising an emission-enhancing material disposed on the surface, the emitted electrons leaving the cathode body through the emission-enhancing material.

57. An electron-emissive device comprising:

a. a cathode body having a thickness equal to at least 100 μ

m;

b. a voltage source; and

c. means for coupling the voltage source to the cathode body so as to impose a body electric field having a body average amplitude across the thickness, imposition of the body electric field causing the cathode body to emit electrons having kinetic energies equal to at least 10% of the energy corresponding to completely loss-free acceleration of an electron through the imposed body electric field across the thickness.

58. The device of claim 57 wherein imposition of the electric field causes the cathode body to emit electrons having kinetic energies equal to at least 40% of the energy corresponding to completely loss-free acceleration of an electron through the imposed body electric field across the thickness.

59. The device of claim 58 wherein the thickness is on the order of 1 mm.

60. The device of claim 58 wherein the body average amplitude over the thickness is between 10⁵ V/m and 10¹⁰ V/m.

61. The device of claim 58 wherein the body average amplitude over the thickness is between 10⁵ V/m and 10⁹ V/m.

62. The device of claim 57 wherein the voltage source is configured to impose an accelerating electric field on the electrons upon their emission from the cathode body.

63. The device of claim 62 wherein the accelerating electric field accelerates emitted electrons, thereby increasing their kinetic energies by an increment, the increment being less than four times the kinetic energies of electrons upon emission from the cathode body.

64. The device of claim 57 wherein the cathode body is of a wide-bandgap semiconductor.

65. The device of claim 57 wherein the cathode body is of a group III nitride.

66. The device of claim 57 wherein the cathode body is of silicon carbide.

67. The device of claim 57 wherein the thickness is on the order of 1 mm.

68. The device of claim 57 wherein the voltage source imposes a dc electric field.

69. The device of claim 57 wherein the cathode body has a surface and further comprising a conductive material disposed on the surface with an interface having a roughness characterized by a radius of curvature less than 15 nm between the cathode body surface and the conductive material, the voltage source electrically contacting the cathode body by means of the conductive material.

70. The device of claim 57 wherein the cathode body has a surface and further comprising an emission-enhancing material disposed on the surface, the emitted electrons leaving the cathode body through the emission-enhancing material.

71. The device of claim 57 further comprising phosphor material arranged to receive emitted electrons, thereby being excited to emit light.

72. The device of claim 71 wherein the phosphor material is in intimate contact with the cathode body so that the emitted electrons enter the phosphor material directly from the cathode body.

73. The device of claim 57 wherein the cathode body is of diamond.

74. The device of claim 73 wherein the cathode body is type Ib diamond.

75. The device of claim 57 wherein the body average amplitude over the thickness is less than 10⁹ V/m.

76. The device of claim 75 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

77. The device of claim 57 wherein the body average amplitude over the thickness is less than 10⁷ V/m.

78. The device of claim 77 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

79. The device of claim 57 wherein imposition of the body electric field causes the cathode body to emit electrons having kinetic energies of at least 50 eV.

80. The device of claim 79 wherein the thickness is on the order of 1 mm.

81. The device of claim 57 wherein the body average amplitude over the thickness is less than 10¹⁰ V/m.

82. The device of claim 81 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

83. The device of claim 57 wherein the body average amplitude over the thickness is less than 10⁸ V/m.

84. The device of claim 83 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

85. The device of claim 57 wherein the body average amplitude over the thickness is less than 10⁶ V/m.

86. The device of claim 85 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

87. An electron-emissive device comprising:

a. a cathode body having a thickness equal to at least 100 μ

m;

b. a voltage source; and

c. means for coupling the voltage source to the cathode body so as to impose a body electric field having a body average amplitude across the thickness, imposition of the body electric field causing the cathode body to emit electrons having kinetic energies of at least 50 eV.

88. The device of claim 87 wherein imposition of the electric field causes the cathode body to emit electrons having kinetic energies equal to at least 40% of the energy corresponding to completely loss-free acceleration of an electron through the imposed body electric field across the thickness.

89. The device of claim 87 wherein the thickness is on the order of 1 mm.

90. The device of claim 87 wherein the cathode body is of diamond.

91. The device of claim 90 wherein the cathode body is type Ib diamond.

92. The device of claim 87 wherein the cathode body is of a wide-bandgap semiconductor.

93. The device of claim 87 wherein the cathode body is of a group III nitride.

94. The device of claim 87 wherein the cathode body is of silicon carbide.

95. The device of claim 87 wherein the voltage source is configured to impose an accelerating electric field on the electrons upon their emission from the cathode body.

96. The device of claim 95 wherein the accelerating electric field accelerates emitted electrons, thereby increasing their kinetic energies by an increment, the increment being less than four times the kinetic energies of electrons upon emission from the cathode body.

97. The device of claim 87 wherein the voltage source imposes a dc electric field.

98. The device of claim 87 wherein the cathode body has a surface and further comprising a conductive material disposed on the surface with an interface having a roughness characterized by a radius of curvature less than 15 nm between the cathode body surface and the conductive material, the voltage source electrically contacting the cathode body by means of the conductive material.

99. The device of claim 87 wherein the cathode body has a surface and further comprising an emission-enhancing material disposed on the surface, the emitted electrons leaving the cathode body through the emission-enhancing material.

100. The device of claim 87 further comprising phosphor material arranged to receive emitted electrons, thereby being excited to emit light.

101. The device of claim 100 wherein the phosphor material is in intimate contact with the cathode body so that the emitted electrons enter the phosphor material directly from the cathode body.

102. The device of claim 87 wherein the body average amplitude over the thickness is less than 10¹⁰ V/m.

103. The device of claim 102 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

104. The device of claim 87 wherein the body average amplitude over the thickness is less than 10⁹ V/m.

105. The device of claim 104 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

106. The device of claim 87 wherein the body average amplitude over the thickness is less than 10⁸ V/m.

107. The device of claim 106 wherein the body average amplitude over the thickness greater than 10⁵ V/m.

108. The device of claim 87 wherein the body average amplitude over the thickness is less than 10⁷ V/m.

109. The device of claim 108 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.

110. The device of claim 87 wherein the body average amplitude over the thickness is less than 10⁶ V/m.

111. The device of claim 110 wherein the body average amplitude over the thickness is greater than 10⁵ V/m.