Growth-front roughening in amorphous silicon films by sputtering

The growth-front roughness of amorphous silicon films grown by dc magnetron sputtering at low pressure has been investigated using atomic force microscopy. The interface width w increases as a power law of deposition time t, w∼t^β, with β=0.41±0.01, and the lateral correlation length ξ grows as ξ∼t^1/z, with 1/z=0.42±0.02. The roughness exponent extracted from height-height correlation analysis is α=0.83±0.03. None of the known growth models can be used to explain the scaling exponents we obtained. Monte Carlo simulations were carried out based on a re-emission model where incident flux distribution, sticking coefficient, and surface diffusion were accounted for in the growth process. The morphology and the scaling exponents obtained from simulations are consistent with the experimental results. When the surface diffusion is switched off in the simulation, columnar structures begin to appear and this is also consistent with the experimental observations of other authors