REFLECTION, ABSORPTION, PHOTOCONDUCTIVITY, AND PHOTO-EMF SPECTRA OF THIN YbS FILMS.

The reflection, absorption, photoconductivity, and photo-emf (the last two for the first time) spectra of thin crystalline ytterbium monosulfide films were obtained at 300 degree K in the photon energy range 0. 3 - 3. 0 eV. The main task of this investigation was to determine the smallest energy gap between the filled 4f levels and the bottom of the conduction band (the published data refer mainly to the maximum of the absorption peak), to identify the nature of the frequency dependence of alpha at the fundamental absorption edge, i. e. , which of the 5d or 6s subbands is the lowest, and to study the photoelectric properties which can give useful information on the energy band structure.