Raman scattering study of PbSe grown on (111) BaF2 substrate

PbSe films were grown on (111)-oriented BaF2 substrates by using molecular beam epitaxy. High resolution x-ray diffraction characterization showed goo d crystalline quality of PbSe films. Both longitudinal optical phonon at 13 5 cm(-1) and transverse optical phonon at 47.6 cm(-1) were observed by Rama n scattering measurements, The Raman tensor calculation demonstrates that b oth transverse-optical and longitudinal-optical (LO) phonons in PbSe crysta l are Raman active on (111)-oriented surface. Furthermore, 2LO phonon at ab out 270 cm(-1) and polaron at about 800 cm(-1) in PbSe, were also observed. The observed Raman frequencies are in good agreement with theoretical calc ulations using point ion model.