Preparation, structure and optical properties of ZnTe and PbTe nanocrystals grown in fluorophosphate glass

ZnTe and PbTe nanocrystals with average radii of 2.42 and 4.25 nm, respectively, were grown in a fluorophosphate glass host. A strong quantum confinement effect was induced as a result of the blue shifted optical absorption due to the ZnTe and PbTe nanocrystals. Optical constants, like the refractive index (n), complex dielectric constant, dissipation factor (tan delta) and optical conductivity (sigma(opt)), were extracted from the experimental transmittance T(lambda) and reflectance R(lambda) data. Moreover, the presence of both the ZnTe and PbTe nanocrystals were confirmed by X-ray diffraction analysis, revealing cubic and hexagonal wurtzite structures, respectively. The results of the optical absorption spectra were confirmed by the similar nanocrystal radii identified using transmission electron microscopy and X-ray diffraction analyses. Raman analysis of the heat-treated glass sample confirmed that bands at 65 and 103 cm(-1) are due to the longitudinal optical (LO) modes of PbTe NCs. Also, the band at 214 cm(-1) is attributed to first harmonic or fundamental LO mode of ZnTe NCs.