# US 5,704,976 A · High temperature, high rate, epitaxial synthesis of diamond in a laminar plasma > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,704,976 A - Document ID: US5704976A - Status: Granted - Kind: A - Application number: 07/697,060 - Filed: 1991-05-08 - Granted: 1998-01-06 - Earliest claimed: 1990-07-06 - Assignees: The United States of America as represented by the Secretary of the Navy - Inventors: Keith A. Snail - Web page: https://patentgrep.com/patent/US5704976A ## CPC - C30B 25/105: {by irradiation or electric discharge} - C30B 29/04: Diamond - C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR ## Abstract A method for synthesizing large, single crystal diamond comprising mixing carbon source and a hydrogen source to form a mixture. The mixture is excited and reacted to form a reactive species in a laminar plasma plume. A substrate having a diamond seed crystal is disposed in the laminar plasma plume while maintaining the diamond seed crystal at a growth temperature between 1100.degree. and 1700.degree. C. for the deposition of diamond, thereby inducing deposition of single crystal diamond on the diamond seed crystal. An apparatus for synthesizing diamond (10;15) comprising a plasma torch (30;31) for producing a laminar plasma plume (44;54). A carbon source (CH.sub.4) and a hydrogen source (H.sub.2,CH.sub.4) are excited and reacted in the laminar plasma plume (44;54) so as to form a reactive species in the laminar plasma plume (44;54). A positioning device is used to dispose a substrate (11) having a diamond seed crystal in the laminar plasma plume (44;54), while a temperature maintaining device (12) is used to maintain the diamond seed crystal at a temperature between 1100.degree. and 1700.degree. C., thereby inducing deposition of single crystal diamond on the diamond seed crystal mounted on substrate (11). ## Claims ### Claim 1 A method for homoepitaxial synthesis of single crystal diamond on a diamond seed crystal, comprising the steps of: (a) mixing a carbon source and a hydrogen source to form a mixture; (b) exciting and reacting said mixture to form a reactive species in a laminar plasma plume; (c) placing the diamond seed crystal in said laminar plasma plume; and (d) maintaining the diamond seed crystal at a temperature above about 1100.degree. C. and at no more than about one atmosphere of pressure. ### Claim 2 (depends on 1) A method as recited in claim 1, wherein: said laminar plasma plume has a laminar flow mode in a region where the diamond seed crystal is placed in step (c). ### Claim 3 (depends on 1) A method as recited in claim 1, wherein step (a) further comprises the substep of: adding a diluent to said mixture. ### Claim 4 (depends on 3) A method as recited in claim 3, wherein: said diluent is argon. ### Claim 5 (depends on 1) A method as recited in claim 1, wherein step (a) further includes the substep of: adding at least one of oxygen and an oxygen containing compound to said mixture. ### Claim 6 (depends on 1) A method as recited in claim 1, wherein step (b) includes the substep of: exciting said mixture with a DC plasma torch. ### Claim 7 (depends on 1) A method as recited in claim 1, wherein step (b) includes the substep of: exciting said mixture with a RF plasma torch. ### Claim 8 (depends on 1) A method as recited in claim 1, wherein step (d) further includes the substep of: maintaining the diamond seed crystal at a temperature under about 1700.degree. C. ### Claim 9 (depends on 1) A method as recited in claim 1, wherein step (d) further includes the substep of: maintaining the diamond seed crystal at a temperature between about 1200.degree.-1500.degree. C. ### Claim 10 (depends on 1) A method as recited in claim 1, wherein: said carbon source is isotopically enriched with .sup.12 C. ### Claim 11 (depends on 1) A method as recited in claim 1, wherein: said carbon source includes finely powdered solid carbon. ### Claim 12 A method for epitaxial synthesis of a single crystal diamond on a substrate including a plurality of diamond seed crystals, comprising the step of: (a) mixing a carbon source and a hydrogen source to form a mixture; (b) exciting and reacting said mixture to form a reactive species in a laminar plasma plume; (c) placing the substrate in said laminar plasma plume; and (d) maintaining the substrate at a temperature between about 1100.degree.-1700.degree. C. and no more than about one atmosphere pressure. ### Claim 13 (depends on 12) A method as recited in claim 12, wherein: the substrate includes a diamond seed crystal. ### Claim 14 (depends on 12) A method as recited in claim 12, wherein step (d) includes the substep of: maintaining the substrate at a temperature between about 1200.degree.-1500.degree. C. ### Claim 15 (depends on 12) A method as recited in claim 12, wherein step (b) includes the substep of: exciting said mixture with a DC plasma torch. ### Claim 16 (depends on 12) A method as recited in claim 12, wherein step (b) includes the substep of: exciting said mixture with a RF plasma torch. ### Claim 17 A method for homoepitaxial synthesis of single crystal diamond on a diamond seed crystal, comprising: (a) mixing methane, hydrogen and argon to form a mixture; (b) exciting and reacting said mixture with a plasma torch to form a reactive species in a laminar plasma plume; (c) placing the diamond seed crystal in said laminar plasma plume; and (d) maintaining the diamond seed crystal at a temperature between about 1200.degree.-1500.degree. C. and no more than about one atmosphere pressure.