Microstructural studies of diamond thin films grown by electron cyclotron resonance-assisted chemical vapor deposition

A detailed investigation of the correlation among intrinsic stress (sigma ( int)), nonuniform stress (sigma (nu)), and phonon lifetime (1/Gamma) was pe rformed in order to obtain a coherent and comprehensive picture of the micr ostructure of diamond thin films grown by the electron cyclotron resonance- assisted chemical vapor deposition (ECR-CVD) technique. It was found that t he diamond growth taking place by the ECR-CVD is different to that taking p lace by the microwave CVD and hot-filament CVD. Point and line defects, rat her than sp(2) C bonds, were found to be the dominant source of both nonuni form stress and reduced phonon lifetime. The surface relaxation mechanism i n these films yields sp(2) C at the expense of strained sp(3) C, resulting in a trade off between diamond yield and crystalline quality. The diamond p recursor that spontaneously forms on the unseeded substrates yielded higher quality diamond than planted diamond seeds. The grain boundary relaxation model proposed by Hoffman accounts well for the observed behavior of the in trinsic stress, thus indicating that microstructural restructuration takes place at the grain boundaries when sufficient time and thermal energy are p rovided. (C) 2000 American Institute of Physics. [S0021-8979(00)09222-7].