Preparation method of high-quality self-support diamond thick film

Abstract

The invention discloses a preparation method of a high-quality self-support diamond thick film. The preparation method comprises the following steps: preparing a high-quality self-support diamond film which is 0.5 to 0.7 mm thick according to a chemical vapor deposition method; conducing grinding and polishing on a nucleation surface of the high-quality self-support diamond film, removing residual carbonide, and preparing a high-quality diamond film which is 1 to 3 mm thick on the treated nucleation surface by taking the treated nucleation surface as a base body, wherein during the two preparation processes, once the thickness of the diamond film is increased by 50 to 100 [mu]m, the methane flow rate is reduced by 0.5 to 1 percent of an initial methane flow rate. The high-quality self-support diamond thick film prepared according to the preparation method is high in quality uniformity, has no crack, and is high in mechanical strength.

Description

technical field [0001] The invention relates to a method for preparing a high-quality self-supporting diamond thick film, belonging to the technical field of superhard material preparation. Background technique [0002] The self-supporting diamond film prepared by chemical vapor deposition (CVD) can be divided into tool grade, heat sink grade, optical grade and electronic grade (or detector grade) according to the quality, among which the tool grade diamond film requires relatively high mechanical strength. Performance, its interior contains a large number of various defects, so it appears gray and black in appearance. The heat sink grade diamond film needs to have relatively high thermal conductivity, and the density of various defects contained in it is lower than that of the tool grade diamond film. Optical-grade diamond film needs to have relatively high optical transmittance, which requires fewer defects in it to ensure its excellent optical transparency in appearance ...

AI Technical Summary

Problems solved by technology

However, due to the difference in expansion coefficient between the diamond film and the base material, when the diamond film is larger than a certain thickness (generally > 1mm), this difference will cause a large thermal stress inside the film, which will cause the film to be completely in contact with the substrate. or partial peeling, while localized cracks or penetrating cracks are prone to occur in the film

In addition, studies have shown that during the CVD process, as the deposition time increases and the film thickness increases, the grain and grain boundary sizes of the diamond film will gradually increase, and the deposition rate will continue to increase. At the same time, the SP in the film 2 The phase content will increase, which will cause the mechanical properties and quality of the diamond film to decrease with the increase of thickness

The reason for this phenomenon is that during the deposition of the diamond film, as the thickness increases, the position of the film surface in the plasma changes, which leads to a change in the concentration ratio of hydrogen atoms and active groups on the film surface. , that is, the concentration of carbon groups on the surface of the film gradually increases, causing the film deposition rate to increase and the quality to decrease

Therefore, it is difficult to prepare a complete diamond thick film with high mechanical strength and uniform quality by MPCVD, which limits the application of this material to a certain extent.

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