Raman spectroscopic determination of residual stresses in diamond films

摘要

Diamond films are attractive for many potential applications due to their superior properties, such as a large band gap, wide range of optical transparency, the highest hardness and Young's modulus as well as thermal conductivity of any known material. Most of the film applications require that the films adhere adequately to the substrate. It has been generally recognized that the presence of residual stress is an important factor affecting the film/substrate adhesion. So, a quantitative evaluation and understanding of the film stresses are necessary for optimizing process conditions and designing reliable diamond films. The residual stresses in chemical-vapor-deposited (CVD) diamond films arise from two sources, namely, intrinsic stress due to film lattice mismatch with the substrate, and thermal stress originated from a thermal-expansion mismatch between the film and the substrate on cooling. In this paper, we report on the determination of residual stresses in CVD diamond films by micro-Raman spectroscopy and by a bi-metal theory and a plate bending theory. It is shown that the residual stresses vary with the film growth. The diamond Raman peak broadening is observed in adherent film, which is actually an effect of biaxial stress on the frequencies of singlet and doublet pho-nons.