Search

Abstract: Microwave plasma chemical vapor deposition (MPCVD) has gained considerable importance due to the capability of producing high quality diamond film, microwave cavity is one key factor for improving the techniques. Reentrant cavities with special structure were proposed, the effective chamber dimension can be changed. Ring shape quartz dielectric window was employed on the bottom side of the substrate holder and so fully shielded from the plasma, which make the cavity has excellent power handing capability. Distribution of electric fields in cavities were simulated. The modeling results show that, after optimization, electric field in chamber exhibits one maximum and homogeneous distribution on substrate, but very weak near the dielectric window, which meet the requirement for design. Proposed reentrant cavities have potential application in MPCVD diamond film with more microwave input power. This study will provide reference for further improvement of MPCVD techniques. [Copyright &y& Elsevier]

Abstract: Chemical vapor deposited diamond thick films for electronic and optical applications must be released without cracks from substrates as freestanding wafers. In the present investigation, the residual stress distribution of diamond thin films deposited by DC arc jet plasma chemical vapor deposition (CVD) at gas recycling mode was analyzed based on wave number shifts in their Raman spectra. The results show that residual compressive stress concentrates at the film''s edge, and this residual stress increases with the increase in deposition temperature. Experimental observation also showed that cracks initiated at the edge of the diamond thick wafer and then propagated towards the center. Effects of the residual stress distribution on diamond thick films detachment were discussed. To release the residual stress, sandwich structure was designed and the metal interlayer was inserted between the diamond films and the substrate. Thick freestanding diamond films (more than 1 mm thick, 60 mm in diameter) were produced by DC arc jet plasma CVD process using Mo substrate with Ti interlayer. [Copyright &y& Elsevier]

A new method of two-step surface pretreatment utilizing two kinds of solutions (KOH:K3[Fe(CN)6]:H2O and H2SO4:H2O2) to etch, respectively, the surface WC and Co in cemented carbide substrates was investigated. Diamond films were deposited by means of the High Current Extended DC Arc Plasma CVD Equipment. The results showed that the two-step method can effectively remove the Co in cemented carbide substrates and obviously roughen the surface of the cemented carbide. As the result, enhancements both on the quality and adhesion of the diamond coatings were observed. [Copyright &y& Elsevier]