Transient nucleation following pulsed-laser melting of thin silicon films

Thin Si films on thermally grown ${\mathrm{SiO}}_2$ layers were completely melted by pulsed-laser irradiation. The molten films cool very rapidly (>${10}^9$ K/s) until bulk nucleation initiates solidification. The quench rate was varied by changing the thickness of the Si or the ${\mathrm{SiO}}_2$ layers. For quenches below ∼${10}^{10}$ K/s the supercooling prior to nucleation was constant and ∼500 K; however, for more rapid quenches, the supercooling increases significantly. This increase is attributed to embryo distributions that fall out of steady state during rapid quenches.