Absorption edge of tin disulfide single crystals

Absorption edge measurements in tin disulfide single crystals have been made. It is found that there is a shoulder in the absorption, just before the onset of band to band transitions, which is caused by transitions from valence band to donor levels (due to a doubly ionizable sulfur vacancy) situated 0.17 eV below the conduction band. It is also found that there are three valence bands which originate by spin-orbit interaction and crystal field splitting. At room temperaure (295 K) the fundamental absorption starts at 2.070±0.001 eV and the transition leading to this is an indirect forbidden one. The photoconductivity maxima, observed at 2.3 eV by earlier workers is here shown to be due to transitions from third valence band to conduction band.