Influence of local heating on micro-Raman spectroscopy of silicon

In micro-Raman spectroscopy strong local heating by the tightly focused laser beam results in an unexpectedly small temperature shift of the Raman peak. The experimental results of shift, broadening, and asymmetry are discussed in view of restricted thermal expansion and a temperature dependent Raman cross section. The Raman signal originates mostly in the wings of the beam profile, where the temperature is substantially lower than at the center. Consequently, the Raman peak shift cannot be used to estimate the maximal surface temperature: despite local melting in the center of the probed spot, the maximal detected shift is only about 2 cm(-1), 10 times less than expected from the center temperature. (C) 2003 American Institute of Physics.