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 good crystalline quality of PbSe films. Both longitudinal optical phonon at 135cm^-1 and transverse optical phonon at 47.6cm^-1 were observed by Raman scattering measurements. The Raman tensor calculation demonstrates that both transverse-optical and longitudinal-optical (LO) phonons in PbSe crystal are Raman active on (111)-oriented surface. Furthermore, 2LO phonon a t about 270cm^-1 and polaron at about 800cm^-1 in PbSe, were also observed. The observed Raman frequencies are in good agreement with theoretical calculations using point ion model.