ODMR and optical investigations of vacancies in metal phosphorus sulfide lattices.

Abstract

Photoluminescence from lamellar chalcogenide lattices of CdPS$\sb3$ and ZnPS$\sb3$ has been examined using the techniques of photoexcitation, photoluminescence and optically detected magnetic resonance (ODMR) spectroscopy. Sharp absorption edges are observed at 3.295 and 3.50 eV in the ZnPS$\sb3$ and CdPS$\sb3$ lattices respectively. The band edge of ZnPS$\sb3$ is about 1 eV higher in energy than previously reported and in agreement with recent band structure calculations. Peaks below the band edge due to stacking disorder were noted. A nearly isotropic ODMR signal without resolved nuclear hyperfine splittings is observed from CdPS$\sb3$ after intercalation with pyridine. The signal is analyzed in terms of weakly exchange coupled donor and acceptor centers with g = 2. ZnPS$\sb3$ crystals exhibit a complex, angle dependent ODMR spectrum prior to intercalation. The ODMR spectrum arises from a strongly coupled, two electron triplet center. Signals were associated with luminescence that is due to octahedral zinc vacancy centers in ZnPS$\sb3.$ The system was modeled as two strongly coupled electron spins with hyperfine interaction due to a nearby I = 1/2 $\sp{31}$P nucleus. Photoluminescence spectra of fullerenes C$\sb{60}$ and C$\sb{70}$ are reported, for both microcrystalline solids and glassy solutions. Tentative analyses for the solution spectra are presented.