US4038216A
Expired / Lapsed
US
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Material and method of making secondary-electron emitters
Assignee: Massachusetts Institute of Technology
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Filing: 1975-08-13
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Granted: 1977-07-26
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Expires: 1995-08-13
Abstract
Abstract Thick, finely-grained films of cermets are fabricated using conventional techniques of sputtering the ceramic and the metal onto a substrate. The cermet is then subjected to differential sputtering in which the metal is sputtered away faster than the ceramic to leave a ceramic-rich surface layer having excellent secondary-electron-emission properties for low-energy incident electrons. Typical of such cermets are MgO/Au, MgO/Pt and MgO/Ag. The presence of metallic particles in the bulk of the films and the small size of the ceramic particles greatly reduce surface charging while allowing the emitter film to be made thick enough to have a long operating life under adverse device conditions.
Inventors
- 👤 Victor E. Henrich
- 👤 John C. C. Fan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:13
CPC Classifications
H; H01; H01J; H01J1/00; H01J1/02; H01J1/32; H04; H04M; H04M3/00; H04M3/42; H04M3/50; H04M3/527; H01J2201/00; H01J2201/32
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
143 words
A fine-grain layer of material comprising a mixture at least 50 vol % of grains of the high-yield secondary-electron emitting material MgO and grains of an electrically conductive material selected from the group consisting of Au, Ag and Pt, the composition of said layer having a greater ratio of said emitting material to said conductive material at the surface of the layer than in the bulk of the layer, the size of the grains of the emitting material is less than 200A and the conducting material of average size of 50-100 A are small enough to allow charge to tunnel from the surface of the grains of emitting material to the surrounding grains of conductive material and the grains of emitting material are large enough so that the emitting material has secondary-electron-emission characteristics close to that of the emitting material in the bulk.
Claim 2
Dependent Claim
143 words
A fine-grain layer of material comprising a mixture at least 50 vol % of grains of the high-yield secondary-electron emitting material MgO and grains of an electrically conductive material selected from the group consisting of Au, Ag and Pt, the composition of said layer having a greater ratio of said emitting material to said conductive material at the surface of the layer than in the bulk of the layer, the size of the grains of the emitting material is less than 200A and the conducting material of average size of 50-100 A are small enough to allow charge to tunnel from the surface of the grains of emitting material to the surrounding grains of conductive material and the grains of emitting material are large enough so that the emitting material has secondary-electron-emission characteristics close to that of the emitting material in the bulk.
Claim 3
Dependent Claim
79 words
A secondary-electron-emitting cermet film consisting of a mixture of particles of MgO and of Au wherein the film consists of 50 to 90 vol % MgO and wherein the average size of the particles of MgO is 150A or less and wherein the average size of the particles of Au is 100 A or less to allow charge to tunnel from the surface of the MgO grains to the surrounding grains Au to eliminate surface charging of the MgO.
Claim 4
Dependent Claim
79 words
A secondary-electron-emitting cermet film consisting of a mixture of particles of MgO and of Au wherein the film consists of 50 to 90 vol % MgO and wherein the average size of the particles of MgO is 150A or less and wherein the average size of the particles of Au is 100 A or less to allow charge to tunnel from the surface of the MgO grains to the surrounding grains Au to eliminate surface charging of the MgO.
Claim 5
Dependent Claim
53 words
The cermet film of claim 2 wherein the surface of the cermet film has a composition of 70 to 100 vol % MgO in order to obtain secondary-electron-emission yields closer to the yield of the pure MgO than would have occurred if the surface composition were the same as that of the bulk.
Claim 6
Dependent Claim
76 words
A secondary-electron-emitting cermet film consisting of a mixture of particles of MgO and of Ag, wherein the film consists of 50 to 90 vol % MgO and wherein the average size of the particles of MgO is 150A or less the average size of the Ag particles is less than 50 A to allow charge to tunnel from the surface of the MgO grains to the surrounding grains Ag to eliminate surface charging of the MgO.
Claim 7
Dependent Claim
76 words
A secondary-electron-emitting cermet film consisting of a mixture of particles of MgO and of Ag, wherein the film consists of 50 to 90 vol % MgO and wherein the average size of the particles of MgO is 150A or less the average size of the Ag particles is less than 50 A to allow charge to tunnel from the surface of the MgO grains to the surrounding grains Ag to eliminate surface charging of the MgO.
Claim 8
Dependent Claim
53 words
The cermet film of claim 4 wherein the surface of the cermet film has a composition of 70 to 100 vol % MgO in order to obtain secondary-electron-emission yields closer to the yield of the pure MgO than would have occurred if the surface composition were the same as that of the bulk.
Claim 9
Dependent Claim
68 words
A secondary-electron emitting cermet film consisting of a mixture of particles of MgO and of Pt wherein the film consists of 50 to 90 vol % MgO and wherein the average size of the particles of MgO and Pt is 100 A or less to allow charge to tunnel from the surface of the MgO grains to the surrounding grains Pt to eliminate surface charging of the MgO.
Claim 10
Dependent Claim
68 words
A secondary-electron emitting cermet film consisting of a mixture of particles of MgO and of Pt wherein the film consists of 50 to 90 vol % MgO and wherein the average size of the particles of MgO and Pt is 100 A or less to allow charge to tunnel from the surface of the MgO grains to the surrounding grains Pt to eliminate surface charging of the MgO.
Claim 11
Dependent Claim
53 words
The cermet film of claim 6 wherein the surface of the cermet film has a composition of 70 to 100 vol % MgO in order to obtain secondary-electron-emission yields closer to the yield of the pure MgO than would have occurred if the surface composition were the same as that of the bulk.
References Cited (Backward Citations)
US3069759A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-07-25 | 1981-01-24 | 1981-07-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-25 | 1985-01-24 | 1985-07-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-25 | 1989-01-24 | 1989-07-26 | $7700.00 | Window Closed / Lapsed |