Femtosecond laser induced surface nanostructuring and simultaneous crystallization of amorphous thin silicon film

Ultrafast pulsed laser irradiation is demonstrated to be able to produce surface nano-structuring and simultaneous crystallization of amorphous silicon thin film in one step laser processing. After fs laser irradiation on 80 nm-thick a-Si deposited on Corning 1737 glass substrate, the color change from light yellow to dark brown was observed on the sample surface. AFM images show that the surface nano-spike pattern was produced on amorphous-Si:H film by fs laser irradiation. Furthermore, micro-Raman results indicate that the a-Si has been crystallized into nanocrystalline Si. Also, the absorptance of the fs laser treated Si thin film was found to increase in the spectrum range of below bandgap compared to original untreated a-Si. The developed process has a potential application in fabrication of high efficiency Si thin film solar cells.