Coherent optical phonon spectroscopy studies of femtosecond-laser modified Sb2Te3 films

We performed time-resolved reflectivity measurements to monitor changes in optical phonon modes in Sb2Te3 thin films under femtosecond laser irradiation. We found that a phonon mode at 3.64 THz appears after high-fluence laser irradiation, in addition to the phonon modes of Sb2Te3. We determined that the additional mode is due to Te segregation as a result of laser-induced decomposition of the Sb2Te3 film. This experiment clearly illustrates the irreversible effects of femtosecond laser irradiation during the measurement of coherent optical phonon dynamics in Sb2Te3. (C) 2010 American Institute of Physics. [doi:10.1063/1.3499742]