Microcrystalline silicon thin film is deposited under different conditions by plasma enhanced chemical vapor deposition. The light stability with different crystallinity and grain size is studied, and the growth mechanism is analyzed using the scaling behavior of roughening surface evolution. Degradation of photoconductivity mainly depends on crystallinity and grain size, but fundamentally, on the growth mechanism. Materials with high crystallinity and large grain size are more stable under light soaking. With the increasing of deposition pressure and input power, growth process transfers to zero diffusion limit growth mechanism, and films deposited present less grain size and poor light stability. (C) 2010 Elsevier Ltd. All rights reserved.