Solidification temperature of silicon surface layer melted by pulsed laser irradiation

Pyrometric measurements of the epitaxial crystallization temperature of Si have been carried out for the 100., 110.and 111.crystallographic orientations of the laser irradiated surfaces of the samples. A ruby laser pulse duration was 10y7 s. Thermal radiation of melted Si was detected in green range of spectrum at the effective wavelength of 0.53 mm. The experimental data obtained have been analyzed on the basis of a nonequilibrium model of laser-induced liquid–crystal phase transitions. According to the experiment, the undercooling of the melt during the epitaxial growth on the 111.plane is about 35 K. The undercooling values corresponding to the 100.and 110.planes are equal and 13"2 K lower than that for the 111.orientation. Two kinetics regimes are considered. They differ in morphology of the liquid–solid interface which is atomically smooth if the interface moves in 111:direction or is atomically rough for the movement in the 110:and 100: directions. The orientation dependence of the epitaxial crystallization seems to be similar to that for the laser amorphization of Si. q1999 Elsevier Science B.V. All rights reserved.