| Utilizing the hot filament chemical vapor deposition(HFCVD), diamond thin films are deposited using CH4 and H2 as the reaction gas source on the surface of single-sided polishing(110) monocrystalline silicon, micro-diamond powder and artificial single crystal diamond by method of control variables, which means only changing parameters such as the filament temperature and deposition pressure while other parameters stay unchangeable. The surface morphology and micro internal structure of the thin film are determined and analyzed by scanning electron microscope(SEM), laser Raman spectroscopy(Raman) and X-Ray diffraction(XRD).The results demonstrated that changing filament temperature could lead to a change in the temperature of the substrate under the condition that the filament and the substrate spacing keep unchanged. When the deposition temperature exceeds 2500 ℃, the thin film would be converted to graphite because of the high temperature carbonization of diamond; when the filament temperature reaches to 2300 ℃, the hydrogen adsorption capacity will increase, and the etching effect on non-diamond phase will also enhance, which caused the gradual emergence of the diamond grains edges and corners. However, the high temperature and hydrogen adsorption capacity could bunch diamond grains and result in the formation of spherical cauliflower; when the filament temperature is 2100 ℃, diamond grain could grow coherently with large grain size and significant angular, and the diamond characteristic peak at 1332cm-1 is very sharp; when the filament temperature comes to even lower, the grain size will be decreased, resulting in the changing of grain shape and unfixable crystal form. As the temperature decreases, the residual stress of the thin film transformed from the compressive stress to the tensile stress.Depositing the diamond thin film on a silicon chip by rising the deposition pressure would increase the diamond grain size gradually. When the pressure comes to 3000 Pa, a characteristic peak at 1135cm-1 appears on Raman spectrum, which is generally considered to be unordered sp3 carbon or nano-diamond peaks. Meanwhile, the diamond grain size is very small observed by SEM, thus the synthesized thin film is the nano dimond film; when the pressure increases, the characteristic peak becomes stronger around 1332cm-1. X-Ray diffraction analyses show that(111) crystal plane, that(110) crystal plane and that(311) crystal plane are included in the synthesized diamond. The diamond grain could be observed clearly by SEM, and the grain size increased while the cube structure grain remained rule and intact. The size of the synthesized deposition diamond thin film becomes maximum when the pressure goes to 7000 Pa, and it grows in close angular. Under this condition the peak of diamond thin film is the most acute, and the product is with minimum non-diamond phase sp2 carbon and minimal residual stress. X-Ray diffraction analyses depicted that the(111) crystal plane took the most significant growth advantage in this way.When analysed the diamond film deposited from the micro diamond powder by Raman spectrum, the characteristic peak of diamond is very sharp, and the nano crystal peak at 1140cm-1 also appears. SEM observation displayed that the thin film grew compactly with small diamond crystal grain. Some micro crystal diamond bunched and in the shape of cauliflower, and the size of diamond crystal grain is in nano-range. With the deposition time increased, the spherical size of bunched micro crystal would be decreased, and the amount of nano-diamond would be increased.The quality of surface morphology and internal structure of the diamond thin film deposited on the surface of artificial single crystal diamond is also excellent. |
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