Intrinsic stress, island coalescence, and surface roughness during the growth of polycrystalline films

During film growth by a variety of techniques, intrinsic tensile stresses c an be created by the coalescence of neighboring islands. Experimental resul ts with diamond films produced by chemical vapor deposition are compared wi th a relatively simple model to demonstrate that a realistic interpretation of these coalescence stresses must account for effects that are associated with surface roughness. First, the interpretation of curvature measurement s during the early stages of film growth must account for this surface roug hness. Also, the experiments show that tensile stresses are induced by grai n boundary formation during continuing growth after the initial island coal escence event. This understanding differs from the traditional interpretati on that continuing intrinsic stress is produced by "templated" growth onto an already strained crystalline lattice. A kinetic model of stress evolutio n during postcoalescence growth is also presented. (C) 2001 American Instit ute of Physics.