Raman measurements of lattice temperature in silicon under intense pulsed laser excitation

The lattice temperature rise in crystalline and ion implanted silicon was measured under pulsed laser annealing conditions. A heat probe technique was used. The probe pulse (FWHM 7 nsec, lambda = 405 nm) with variable delay was provided by either a N2 laser-pumped dye laser while the heat pulse was provided by a N2 laser-pumped dye laser (lambda = 485 nm) or by a doubled Nd:YAG laser (FWHM 10 nsec, lambda = 532 nm). Lattice temperatures were inferred directly from the Stokes to anti Stokes count ratio of the one phonon Raman line. Suitable correction factors were applied to the Raman ratio to compensate for the spectral dependence of the Raman cross section and the absorption constant. A new experimental technique which is based on time reversal invariance was developed to find the correction factors. The anomalously low lattice temperatures show unequivocally that the high reflectively phase is not associated with normal molten silicon unless an unreasonably large cooling rate is assumed.