Role of grains in protocrystalline silicon layers grown at very low substrate temperatures and studied by atomic force microscopy

Abstract

We have investigated the role of the sample thickness and silane dilution on the structure and electronic properties of protocrystalline silicon thin films deposited at very low substrate temperatures (∼80 ° C) . Coincidence of the maxima in surface roughness and ambipolar diffusion length ( ≳100 nm) with formation of the network of interconnected crystalline grain aggregates was observed. While the presence of the isolated grain aggregates improves the photoconductive properties before the percolation threshold is reached, further increase in crystallinity may have opposite effect due to detrimental role of increasing concentration of the defective grain boundaries.