Near-infrared femtosecond laser-induced crystallization of amorphous silicon

Abstract

Amorphous silicon (a-Si) was crystallized by femtosecond laser annealing (FLA) using a near-infrared (lambdaapproximate to800 nm) ultrafast Ti:sapphire laser system. The intense ultrashort laser pulses lead to efficient nonlinear photoenergy absorption and the generation of very dense photoexcited plasma in irradiated materials, enabling nonlinear melting on transparent silicon materials. We studied the structural characteristics of recrystallized films and found that FLA assisted by spatial scanning of laser strip spot constitutes superlateral epitaxy that can crystallize a-Si films with largest grains of similar to800 nm, requiring laser fluence as low as similar to45 mJ/cm(2), and low laser shots. Moreover, the optimal annealing conditions are observed with a significant laser-fluence window (similar to30%). (C) 2004 American Institute of Physics.