Optical and Photoelectric Properties of the Lead Chalcogenides

The reflection spectra of PbS, PbSe, and PbTe have been measured in the 14 to 26 eV region using as a source the DESY‐synchrotron. Three peaks are observed for PbSe and PbTe and two for PbS, corresponding to transitions from the outermost d‐levels of the Pb core to the conduction bands. In order to find out the relationship between these peaks and the spin–orbit splitting of the d‐core levels, X‐rays photoemission measurements (ESCA) have been performed. It is concluded that this spin‐orbit splitting of the d‐core levels does not appear directly in the optical spectra. A simple model is given to interpret these spectra. The valence band, and other core levels of binding energies in the range of the Kα line (1486.6 eV) aluminium‐X‐ray source have also been studied. The binding energies, splittings, and chemical shifts obtained are discussed and compared with theoretical calculations. The most intense ESCA lines exhibit satellites which can be associated with lines produced by the excitation of valence plasmons. The effects of adsorbed oxygen on the ESCA spectra are also discussed.