NONLINEAR STABILITY ANALYSIS OF THE GROWTH SURFACE DURING DIAMOND CHEMICAL-VAPOR-DEPOSITION

The morphological stability of the solid-gas interface under condition s of diffusive transport of reactant species towards the surface durin g the chemical vapor deposition process is analyzed using linear and n onlinear perturbation theories. The Landau coefficient, which represen ts the nonlinear growth rate, is calculated using the direct method of undetermined coefficients. A dispersive relation is derived which rel ates the effects of species diffusive transport towards the growing in terface, surface diffusion, and geometrical factors with the stability of perturbations on the interface. The resulting relation is applied to the diamond chemical vapor deposition process. Linear and nonlinear instability of the interface is obtained for diamond chemical vapor d eposition conditions. Linear instability increases but the Landau coef ficient becomes larger, indicating greater nonlinear stability as the reactor pressure increases, although both linear and nonlinear analyse s suggest more stability as the reactor temperature increases. However , during typical diamond growth conditions, it is predicted that the d iamond-gas interface is unstable to both infinitesimal and finite ampl itude disturbances. (C) 1998 American Institute of Physics. [S0021-897 9(98)07611-7].