Optical absorption in PbSe spherical quantum dots embedded in glass matrix

A phosphate glass embedded with PbSe semiconductor quantum dots (QDs) has been synthesized and investigated. Optical absorption spectra of PbSe spherical QDs have been studied both theoretically and experimentally. Theoretical analysis of the energy spectra and optical transitions has been carried out in the framework of four-band k.p model taking full account of anisotropy effects. It is demonstrated that the strong anisotropy of the energy bands of bulk PbSe gives rise to additional optical transitions in the quantum dots. These anisotropy-induced optical transitions have been clearly observed in the measured absorption spectra of the PbSe quantum dots. The calculated energy positions of the optical transitions are in good agreement with experiment. Five optical transitions were distinguished and interpreted in the absorption spectra measured at T = 12 K. For the set of samples with a narrow size distribution of PbSe QDs (diameters in range of 40-110 Angstrom), the energies of three or four optical transitions have been determined from the measured absorption spectra at T = 300 K. The calculated dependencies of the energies of the first five optical transitions with QD size are in good agreement with those obtained from the experimental data. (C) 2000 American Institute of Physics. [S0021-8979(00)07814-2].