| 主权项 |
1. A process for depositing diamond on a substrate, by chemical vapor deposition, this process comprising at least:
a) an initiation step; b) a nucleation step; c) a growth step, the growth step comprising two or more sequences of two successive phases, the first phase being a coalescence phase without application of an electric field and the second phase being an etching and a nucleation phase with application of a negative electric field that creates a plasma, carried out under the following conditions:
duration of each phase between 20 and 40 minutes;application of a gas chosen from:a H2/CH4/X mixture in which X represents a noble or inert gas, with a volume percentage of noble or inert gas relative to the total volume of the mixture of between 0 and 10% and with a volume percentage of CH4 relative to the total volume of the mixture of between 0.5 and 1.5%; a H2/CH4/CO2 mixture, volume of the CH4/CO2 mixture relative to the total volume of the gases of between 0.5 and 5% for a ratio of the volumes of CH4/CO2 of between 0.2 and 0.8;
a CH4/CO2 mixture with a ratio of the volumes of CH4/CO2 of between 0.4 and 0.6; the total flow rate of the gases being greater than 10 cm3/min, and the pressure being between 1 and 60 hPa, and wherein gas flow rates and gas mixtures applied in the etching and nucleation phase are the same as gas flow rates and gas mixtures applied in the coalescence phase, and wherein the diamond layer obtained is in the form of micron size pyramidal aggregates having flat bases essentially constituted of diamond nanograins, that is to say of diamond grains, the size of which, defined by the diameter of the grains, ranges from 1 to 100 nm. |
