CRYSTALLINE QUALITY AND RESIDUAL-STRESSES IN DIAMOND LAYERS BY RAMAN AND X-RAY-DIFFRACTION ANALYSES

A major problem for diamond coating applications is that diamond films tend to exhibit poor adherence on many substrates and typically disbond at thicknesses of the order of a few micrometers principally because of residual stresses. Residual stresses are composed of thermal mismatch stresses and intrinsic tensile film stresses induced during him growth, Diamond films were deposited in a classical tubular microwave plasma reactor from hydrocarbon-hydrogen-oxygen gas mixtures. The stress level was investigated as a function of the gaseous composition (especially oxygen concentration) and deposition temperature (700-900 degrees C). Thermal stress was directly calculated from Hooke's law using a biaxial Young's modulus value of 1230 GPa for polycrystalline diamond. Total diamond film stress was directly determined by the radius of curvature method and by x-ray diffraction using the sin(2) psi method. The microdistorsions and the size of the coherently diffracting domains have been determined from the broadening of the diffraction peak. When coupled also with a Raman study, these investigations allow discussion of the origin of intrinsic stress. (C) 1995 American Institute of Physics.