Effects of residual stress distribution on the cracking of thick freestanding diamond films produced by DC arc jet plasma chemical vapor deposition operated at gas recycling mode

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.