Infra-red transparent optical components

• US 4,704,339 A
• Filed: 01/13/1986
• Issued: 11/03/1987
• Est. Priority Date: 10/12/1982
• Status: Expired due to Term

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: Lettington, Alan H., Green, Geoffrey W.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/818,496
• Time in Patent Office: 659 Days
• Field of Search: 428/688, 428/689, 428/408, 428/409, 350/1.1, 350/1.4, 350/1.7, 350/1.3, 204/192 R, 204/192 P
• US Class Current: 428/689
• CPC Class Codes: C23C 14/0036 Reactive sputtering
• CPC Class Codes: C23C 14/027 Graded interfaces
• CPC Class Codes: C23C 16/0272 Deposition of sub-layers, e.g. to promote the adhesion of the main coating
• CPC Class Codes: C23C 16/029 Graded interfaces
• CPC Class Codes: C23C 16/32 Carbides
• CPC Class Codes: C23C 16/325 Silicon carbide
• CPC Class Codes: G02B 1/12 by surface treatment, e.g. by irradiation
• CPC Class Codes: Y10T 428/31 Surface property or characteristic of web, sheet or block

Abstract

A method of coating a substrate in a glow discharge chamber uses a source of hydrocarbon and another element. Butane and germane are used to deposit a coating of Ge_x C_1-x where 0<x<1 onto a germanium substrate. The substrate temperature is maintained above 400° C., typically 530° C., during growth to prevent inclusion of H₂ in the coating. The presence of Ge in the coating allows thick, stain-free, layers to be grown. Alternatively, butane and silane may be used to deposit Si_x C_1-x. Varying the proportions of the hydrocarbon and germane or silane allows a variation in the value of x.

A method of growing a combined layer of at least a first and a second material in glow discharge chamber. A target cathode formed on the first material, e.g., Si, Ge, W is arranged in the chamber and spaced from a substrate to be coated. Argon gas and a gas of the second material, e.g., a hydrocarbon, are admitted into the chamber and a glow discharge established. Hydrocarbon ions from the glow discharge plasma strike and deposit on the cathode target. Argon ions sputter off atoms of both C and bulk target material, e.g., Si, Ge, or W, which deposit onto the substrate and gradually build up a combined layer of, e.g., Si_x C_1-x, Ge_x C_1-x, W_x C_1-x wherein 0<x<1.

Optical lens components, infra-red transparent, made from these processes are also disclosed.

Claims

1. An infra-red transparent optical component comprising a germanium, ZnS or ZnSe substrate coated on at least one surface with a layer of Ge_x C_1-x, where 0<

X<

1, said layer being substantially infra-red transparent, hydrogen-free and strain-free.

3. The infra-red transparent optical component according to claim 1, wherein the value of x varies across the thickness of the layer.

5. The infra-red transparent optical component according to claim 1 wherein said substrate is coated with a plurality of said layers, each said layer having a different value of x, the last such layer non-adjacent to said substrate having the lowest value of x.

7. The infra-red transparent optical component according to claim 1, wherein a bonding layer is provided between the substrate and the layer.

9. An infra-red transparent optical component according to claim 1, wherein a said layer is about 1 to 10 μ

m thick.

10. An infra-red transparent optical component according to claim 1, wherein said layer is at least about 1 μ

m thick.

11. The infra-red transparent optical component according to claim 9, wherein the value of x varies across the thickness of the layer.

12. The infra-red transparent optical component according to claim 9, wherein said substrate is coated with a plurality of said layers, each said layer having a different value of x, the last such layer non-adjacent to said substrate having the lowest value of x.

13. The infra-red transparent optical component according to claim 12, wherein a bonding layer is provided between the substrate and the first layer.

15. The infra-red transparent optical component according to claim 13, wherein the value of x varies across the thickness of the layer.

2. An infra-red transparent optical component comprising a ZnS, a germanium, or a ZnSe substrate coated on at least one surface with a layer of Si_x C_1-x, where 0<

x<

1, said layer being substantially infra-red transparent, hydrogen-free, and strain-free.

4. The infra-red transparent optical component according to claim 2, wherein the value of x varies across the thickness of the layer.

6. The infra-red transparent optical component according to claim 2, wherein said substrate is coated with a plurality of coating layers, each said layer having a different value of x, the last such layer non-adjacent to said substrate having the lowest x value.

8. The infra-red transparent optical component according to claim 2, wherein a bonding layer is provided between the substrate and the layer.

14. An infra-red transparent optical component according to claim 2, wherein the layer is about 1 μ

m to 10 μ

m thick.

16. The infra-red transparent optical component according to claim 2, wherein the layer is at least about 1 μ

m thick.

17. The infra-red transparent optical component according to claim 14, wherein said substrate is coated with a plurality of layers, each said layer having a different value of x, the last such layer non-adjacent to said substrate having the lowest x value.