Local photoconductivity correlation with granular structure of microcrystalline silicon thin films

Optical beam induced current (OBIC) and atomic force microscopy (AFM) experiments are applied to determine the opto-electronic properties of microcrystalline silicon films prepared by pulsed interference laser crystallization. OBIC reveals built-in fields at grain boundaries, where photocurrents are generated even without external bias. Shifting the laser spot of ∼0.8 μm diameter over grain boundaries produces 180° phase shifts of the photoresponse detected by lock-in technique. This change allows the identification of grain boundaries with a spatial resolution of ∼100 nm. The results are in reasonable agreement with AFM experiments.