Parameterization of a-Si crystallization by continuous-wave green laser irradiation: from single spot to large area

An advantage of laser crystallization over conventional heating methods is its ability to limit rapid heating and cooling to thin surface layers. In the present work, thin-film amorphous-silicon samples were irradiated with a continuous-wave green laser source. Laser irradiated spots were produced by using different laser powers and irradiation times. Micro-Raman spectroscopy was used to study the crystallization induced on the irradiated surface. Both laser peak power density and irradiation time are identified as key variables in the crystallization process, but within the parametric window considered, the enhancement of the crystalline factor, is more sensitive to the power density than to the irradiation time. The optimum parameters are then used for crystallizing a large sample area by means of overlapped laser scanned lines. Ellipsometric data experimentally show that the whole volume of a micron-thick sample is crystallized.