Raman Scattering Study of PbSe Grown on (111) BaF 2 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 135 cm-1 and transverse optical phonon at 47.6 cm-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 at about 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 calculations using point ion model.