Field-emission cathode capable of forming an electron beam having a high current density and a low ripple

• US 5,929,557 A
• Filed: 11/03/1997
• Issued: 07/27/1999
• Est. Priority Date: 11/01/1996
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Takahashi, Masaaki, Makishima, Hideo
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): Smith, Michael J.
• Application Number:
  US08/962,874
• Time in Patent Office: 631 Days
• Field of Search: 313/309, 313/351, 313/336, 313/495, 313/494
• US Class Current: 313/309
• CPC Class Codes: H01J 2223/04 Cathodes
• CPC Class Codes: H01J 23/06 Electron or ion guns
• CPC Class Codes: H01J 3/022 with microengineered cathode, e.g. Spindt-type

Abstract

A field-emission cold cathode has a conductive cold-cathode substrate on which a plurality of conical emitters and a base insulator layer are formed. A ring-shaped gate electrode, a plate-shaped inner electrode, and a ring-shaped outer electrode are formed on the base insulator layer with the ring-shaped gate electrode disposed between the plate-shaped inner electrode and the ring-shaped outer electrode. A voltage supplying unit supplies the ring-shaped gate electrode, the plate-shaped inner electrode, and the ring-shaped outer electrode with a gate voltage, an inner electrode voltage, and an outer electrode voltage, each referenced to a substrate potential of the conductive cold-cathode substrate, wherein the gate voltage is higher than each of the inner electrode voltage and the outer electrode voltage.

Claims

1. A field-emission cold cathode for use in an electron gun to radiate an electron beam therefrom along a central axis in a forward direction, said field-emission cold cathode comprising:

a conductive cold-cathode substrate having a substrate center concentric with said central axis and having a principal surface perpendicular to said central axis, said conductive cold-cathode substrate being supplied with a substrate potential;

a plurality of conical emitters formed on said principal surface in a ring-shaped emitter region around said substrate center, each conical emitter having a tip from which electrons emit in the forward direction;

a base insulator layer formed on said principal surface of said cold-cathode substrate, said base insulator layer having a plurality of base-insulator holes surrounding said respective conical emitters with spaces left therebetween;

a ring-shaped gate electrode formed on said base insulator layer in a ring-shaped gate region facingly opposed to said ring-shaped emitter region through said base insulator layer, said ring-shaped gate electrode having a gate center concentric with said central axis and having a plurality of gate holes which are aligned with said respective base insulator holes so as to surround said conical emitters, said ring-shaped gate electrode for extracting electrons emitted from said conical emitters to make the electrons radiate as an electron beam;

a plate-shaped inner electrode formed on said base insulator layer in an inner region enclosed by said ring-shaped gate electrode with a ring-shaped inner space left therebetween;

a ring-shaped outer electrode formed on said base insulator layer in an outer region surrounding said ring-shaped gate electrode with a ring-shaped outer space left therebetween; and

voltage supplying means for supplying said ring-shaped gate electrode, said plate-shaped inner electrode, and said ring-shaped outer electrode with a gate voltage, an inner-electrode voltage, and an outer-electrode voltage, respectively, referenced to the substrate potential of said conductive cold-cathode substrate, said gate voltage being higher than said inner-electrode voltage and said gate voltage being higher than said outer-electrode voltage.

2. A field-emission cold cathode as claimed in claim 1, further comprising a plate-shaped upper inner insulator layer formed on said base insulator layer in said inner region, said plate-shaped inner electrode being formed on said plate-shaped upper inner insulator layer.

3. A field-emission cold cathode as claimed in claim 1, further comprising a ring-shaped upper outer insulator layer formed on said base insulator layer in said outer region, said ring-shaped outer electrode being formed on said ring-shaped upper outer insulator layer.

4. A field-emission cold cathode as claimed in claim 1, further comprising a plate-shaped upper inner insulator layer formed on said base insulator layer in said inner region and a ring-shaped upper outer insulator layer formed on said base insulator layer in said outer region, said plate-shaped inner electrode being formed on said plate-shaped upper inner insulator layer, said ring-shaped outer electrode being formed on said ring-shaped upper outer insulator layer.

5. A field-emission cold cathode for use in an electron gun for radiating an electron beam therefrom along a central axis in a forward direction, said field-emission cold cathode comprising:

a conductive cold-cathode substrate having a substrate center concentric with said central axis and a principal surface perpendicular to said central axis, said conductive cold-cathode substrate supplied with a substrate potential;

a plurality of conical emitters formed on said principal surface in a ring-shaped emitter region around said substrate center, each conical emitter having a tip from which electrons emit in the forward direction;

a base insulator layer formed on said principal surface, said base insulator layer having a plurality of base-insulator holes surrounding respective said conical emitters with spaces left therebetween;

a gate electrode formed on said base insulator layer, said gate electrode having a gate center concentric with said central axis and having a plurality of gate holes which are aligned with respective said base-insulator holes so as to surround said conical emitters, said gate electrode for extracting electrons emitted from said conical emitters to make the electrons radiate as an electron beam;

an upper insulator layer formed on said gate electrode, said upper insulator layer having a plurality of upper-insulator holes which are aligned with the base-insulator holes via the gate holes;

a ring-shaped focusing electrode formed on said upper insulator layer in a ring-shaped focusing region facingly opposed to the ring-shaped emitter region through said upper insulator layer and said gate electrode, said ring-shaped focusing electrode having a focusing center concentric with said central axis and having a plurality of focusing holes which are aligned with the respective said gate holes via the upper-insulator holes;

a plate-shaped inner electrode formed on said upper insulator layer in an inner region enclosed by said ring-shaped focusing electrode with a ring-shaped inner space left therebetween;

a ring-shaped outer electrode formed on said upper insulator layer in an outer region surrounding said ring-shaped focusing electrode with a ring-shaped outer space left therebetween; and

voltage supplying means for supplying said ring-shaped focusing electrode, said plate-shaped inner electrode, and said ring-shaped outer electrode with a focusing voltage, an inner-electrode voltage, and an outer-electrode voltage, respectively, referenced to the substrate potential of said conductive cold-cathode substrate, said focusing voltage being higher than said inner-electrode voltage and said focusing voltage being higher than said outer-electrode voltage.

6. A cold-cathode electron gun for radiating an electron beam therefrom along a central axis in a forward direction, comprising:

a ring-shaped cold cathode having a cathode opening coaxial with said central axis, said ring-shaped cold cathode for emitting electrons along the central axis to make said electrons radiate as said electron beam, said ring-shaped cold cathode including a conductive cathode substrate supplied with a substrate potential, said ring-shaped cold cathode having a ring-shaped gate electrode that includes a ring-shaped electron emission region, wherein said ring-shaped gate electrode is disposed opposed to said conductive cathode substrate, and wherein said ring-shaped electron emission region defines a ring-shaped area concentric to said central axis;

a cylindrical outer Wehnelt electrode surrounding said ring-shaped cold cathode with a ring-shaped outer space left thererbetween, said cylindrical outer Wehnelt electrode extending in the forward direction from said ring-shaped cold cathode;

a rod-shaped inner Wehnelt electrode surrounded by said ring-shaped cold cathode with a ring-shaped inner space left therebetween, said rod-shaper inner Wehnelt electrode extending in the forward direction from said ring-shaped cold cathode; and

voltage supplying means for supplying said ring-shaped gate electrode, said cylindrical outer Wehnelt electrode, and said rod-shaped inner Wehnelt electrode with a gate voltage, an outer Wehnelt voltage, and an inner Wehnelt voltage, respectively, referenced to said substrate potential, wherein said gate voltage is higher than said outer Wehnelt voltage and said gate voltage is higher than said inner Wehnelt voltage.

7. A cold-cathode electron gun as claimed in claim 6, wherein said ring-shaped electron emission region is defined by an inside diameter D_I and an outside diameter D_O, and wherein said inside diameter D_I and said outside diameter D_O are satisfied by the following relationship:

D_I /D_O ≧

0.8.

8. A cold-cathode electrode gun as claimed in claim 6, wherein said cylindrical outer Wehnelt electrode has a height which is higher than that of said rod-shaped inner Wehnelt electrode, wherein said height is a distance along said center axis from said conductive cathode substrate.

9. A cold-cathode electrode gun as claimed in claim 6, wherein said cylindrical outer Wehnelt electrode has an internal wall which is apart from said electron emission region by an outer distance, and wherein said rod-shaped inner Wehnelt electrode has an external wall which is apart from said electron emission region by an inner distance, wherein said inner distance is longer than said outer distance.