HIGH COLOUR DIAMOND LAYER

• US 20100015438A1
• Filed: 06/22/2006
• Published: 01/21/2010
• Est. Priority Date: 06/22/2005
• Status: Active Grant

• Current Assignee: Element Six Technologies US Corporation (Anglo American PLC)
• Original Assignee: Element Six (Holdings) Ltd. (Anglo American PLC)
• Inventors: Friel, Ian, Martineau, Philip Maurice, Scarsbrook, Geoffrey Alan, Twitchen, Daniel James, Williams, Stephen David
• Granted Patent: US 7,964,280 B2
• Time in Patent Office: Days
• US Class Current: 428/332
• CPC Class Codes: C23C 16/006 characterized by the colour of the layer
• CPC Class Codes: C23C 16/27 Diamond only
• CPC Class Codes: C23C 16/278 doping or introduction of a secondary phase in the diamond
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/105 by irradiation or electric discharge
• CPC Class Codes: C30B 29/04 Diamond
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

A method of producing CVD diamond having a high colour, which is suitable for optical applications, for example. The method includes adding a gaseous source comprising a second impurity atom type to counter the detrimental effect on colour caused by the presence in the CVD synthesis atmosphere of a first impurity atom type. The described method applies to the production of both single crystal diamond and polycrystalline diamond.

Claims

1. A method of producing a CVD diamond layer having high colour comprising:

(i) providing a substrate;

(ii) providing a CVD synthesis atmosphere in which there exists a first gas comprising a first impurity atom type which has a detrimental effect on the colour of the produced diamond layer; and

(iii) adding into the synthesis atmosphere a second gas comprising a second impurity atom type,

wherein the first and second impurity atom types are different;

the type and quantity of the second impurity atom type is selected to reduce the detrimental effect on the colour caused by the first impurity atom type so as to produce a diamond layer having high colour;

and the first and second impurity atom types are independently nitrogen or atoms which are solid in the elemental state.

2. The method of claim 1 wherein the CVD diamond layer is a single crystal.

3. The method of claim 1 wherein the CVD diamond layer is polycrystalline.

4. The method of claim 1 wherein the first impurity atom type is nitrogen and the second impurity atom type is selected from silicon, boron, phosphorus or sulphur.

5. The method of claim 4 wherein the second impurity atom type is silicon.

6. The method of claim 4 wherein the second impurity atom type is boron.

7. The method of claim 1 wherein the first impurity atom type is silicon, boron, phosphorus or sulphur and the second impurity atom type is nitrogen.

8. The method of claim 7 wherein the first impurity atom type is silicon.

10. The method of claim 5 wherein the concentration of nitrogen in the majority volume of the diamond layer is less than or equal to 2×

10¹⁷ atoms/cm³ and the concentration of silicon in the majority volume of the diamond layer is less than or equal to 2×

10¹⁸ atoms/cm³.

11. The method of claim 5 wherein the ratio of the concentration of nitrogen to the concentration of silicon in the majority volume of the diamond layer is from 1:

20 to 20;

1.

12. The method of claim 5 wherein the gas comprising nitrogen is present in the synthesis atmosphere at a concentration of greater than 100 ppb and the gas comprising silicon is present in the synthesis atmosphere at a concentration of greater than 10 ppb.

13. The method of claim 6 wherein the ratio of the concentration of nitrogen to the concentration of boron in the majority volume of the diamond layer is from 1:

2 to 2;

1.

14. The method of claim 6 wherein the gas comprising nitrogen is present in the synthesis atmosphere at a concentration of greater than 100 ppb and the gas comprising boron is present in the synthesis atmosphere at a concentration of greater than 0.5 ppb.

15. The method of claim 1 wherein the produced CVD diamond layer has an increased normalized free exciton intensity compared to a method where the second gas comprising a second impurity type atom is not added.

16. The method of claim 1 any of the preceding claims wherein the produced CVD diamond layer has an increase in carrier mobility, carrier lifetime and/or charge collection distance compared to a method where the second gas comprising a second impurity type atom is not added.

17. The method of claim 1 any of the preceding claims wherein the synthesis atmosphere comprises a concentration of the gas comprising nitrogen which has not been added deliberately of greater than 300 ppb.

18. The method of claim 1 any of the preceding claims wherein the first gas is not added in a controlled manner.

19. The method of claim 1 wherein the diamond layer is greater than 0.1 mm in thickness.

31. The method of claim 1 wherein the CVD diamond layer is a single crystal, and wherein the majority volume of the diamond layer has at least one of the following features:

a) an absorption spectrum measured at room temperature such that the colour of a standard 0.5 ct round brilliant would be better than K;

b) an absorption coefficient at 270 nm measured at room temperature which is less than 1.9 cm<sup>−

1</sup>;

c) an absorption coefficient at 350 nm measured at room temperature which is less than 0.90 cm<sup>−

1</sup>;

d) an absorption at 520 nm of less than 0.30 cm<sup>−

1</sup>;

or

e) an absorption at 700 nm of less than 0.12 cm<sup>−

1</sup>.

32. The method of claim 1 wherein the CVD diamond layer is polycrystalline, and wherein the majority volume of the diamond layer has at least one of the following features:

a) an absorption coefficient at 270 nm measured at room temperature which is less than 1.9 cm<sup>−

1</sup>;

b) an absorption coefficient at 350 nm measured at room temperature which is less than 0.90 cm<sup>−

1</sup>;

c) an absorption at 520 nm of less than 0.30 cm<sup>−

1</sup>; and

d) an absorption at 700 nm of less than 0.12 cm<sup>−

1</sup>.

33. The method of claim 1 wherein the CVD diamond layer is a single crystal and wherein the diamond layer is formed into a gemstone having three orthogonal dimensions greater than 2 mm, where at least one axis lies either along the <

100>

crystal direction or along the principle symmetry axis of the gemstone.

34. A CVD diamond layer produced by the method of claim 1.

43. An optical element comprising the CVD diamond layer produced according to the method of claim 1.

44. An electrical or electronic element comprising the CVD diamond layer produced according to the method of claim 1.

45. A CVD diamond layer produced according to the method of claim 1 having a thickness greater than 0.1 mm.

46. A CVD single crystal diamond layer produced according to the method of claim 1 in the form of a gemstone.

47. A CVD single crystal diamond layer according to claim 46 having three orthogonal dimensions greater than 2 mm, wherein at least one axis lies along the <

100>

crystal direction or along the principle symmetry axis of the gemstone.

48. A CVD single crystal diamond layer according to claim 46 having a clarity of at least SH on the GIA gem grading scale.

51. The method of claim 8 wherein the concentration of nitrogen in the majority volume of the diamond layer is less than or equal to 2×

10¹⁷ atoms/cm³ and the concentration of silicon in the majority volume of the diamond layer is less than or equal to 2×

10¹⁸ atoms/cm³.

52. The method of claim 8 wherein the ratio of the concentration of nitrogen to the concentration of silicon in the majority volume of the diamond layer is from 1:

20 to 20;

1.

53. The method of claim 8 wherein the gas comprising nitrogen is present in the synthesis atmosphere at a concentration of greater than 100 ppb and the gas comprising silicon is present in the synthesis atmosphere at a concentration of greater than 10 ppb.

9. The method of 7 wherein the first impurity atom type is boron.

54. The method of claim 9 wherein the ratio of the concentration of nitrogen to the concentration of boron in the majority volume of the diamond layer is from 1:

2 to 2;

1.

55. The method of claim 9 wherein the gas comprising nitrogen is present in the synthesis atmosphere at a concentration of greater than 100 ppb and the gas comprising boron is present in the synthesis atmosphere at a concentration of greater than 0.5 ppb.

20. A method of producing a CVD diamond layer, comprising:

(i) providing a substrate;

(ii) providing a CVD synthesis atmosphere in which there exists a concentration of nitrogen which is not deliberately added of greater than 300 ppb; and

(iii) adding into the synthesis atmosphere a second gas comprising a second impurity atom type other than nitrogen,

wherein the second impurity atom type is added in a controlled manner in an amount that reduces the detrimental effect on the colour caused by the nitrogen so as to produce a diamond layer having high colour; and

the second impurity atom type is solid in the elemental state.

21. A method of producing a CVD diamond layer comprising:

(i) providing a substrate; and

(ii) adding into a CVD synthesis atmosphere a gaseous source comprising silicon.

22. The method of claim 21 wherein the CVD diamond layer is a single crystal.

23. The method of claim 21 wherein the CVD diamond layer is polycrystalline.

24. The method of claim 21 wherein the method comprises one or more of the following features:

(1) the layer is grown to greater than 0.1 mm thickness;

(2) the substrate is a diamond substrate having a surface which is substantially free of crystal defects such that a revealing plasma etch would reveal a density of surface etch features related to defects below 5×

10³/mm²;

(3) the duration of the synthesis of the single crystal diamond layer is at least 50 hours; and

(4) the substrate comprises multiple separated single crystal diamond substrates.

25. The method of claim 21 wherein the concentration of silicon in the majority volume of the diamond layer is less than or equal to 2×

10¹⁸ atoms/cm³.

26. The method of claim 21 wherein the addition of silicon reduces an adverse effect on a property of the produced diamond layer caused by the presence of an impurity atom type.

27. The method of claim 26 wherein the impurity atom type is nitrogen.

28. The method of claim 26 wherein the property is colour and adding silicon produces a CVD diamond layer having high colour.

29. The method of claim 26 wherein the property is free exciton emission of the diamond layer and adding silicon produces a CVD diamond layer with an increased normalized free exciton intensity compared to a method where silicon is not added.

30. The method of claim 26 wherein the property is at least one of:

carrier mobility;

carrier lifetime; and

charge collection distance and adding silicon produces a CVD diamond layer with an increase in carrier mobility, carrier lifetime and/or charge collection distance compared to a method where silicon is not added.

35. A CVD diamond layer comprising an impurity atom type selected from silicon, sulphur or phosphorus, wherein the diamond layer has high colour.

36. The CVD diamond layer of claim 35 wherein the majority volume of the diamond layer comprises from 1015 to 2×

10¹⁸ atoms/cm³ of an impurity atom type selected from silicon, sulphur or phosphorus.

37. The CVD diamond layer of claim 35 wherein the impurity atom type is silicon.

38. The CVD diamond layer of claim 35 wherein the diamond layer has high colour.

39. The CVD diamond layer of claim 35 wherein the layer has a thickness of greater than 1 mm.

40. The CVD diamond layer of claim 35 wherein the layer has a birefringence of less than 1×

10<sup>−

3</sup> over a volume greater than 0.1 mm³.

41. The CVD diamond layer of claim 35 wherein the diamond layer is a single crystal.

42. The CVD diamond layer of claim 35 wherein the diamond layer is polycrystalline.

49. (canceled)

50. (canceled)