Characterization of Mo-doped CuAlS 2 Single Crystals by PL and ESR

Near-infrared photoluminescence (PL) and electron spin resonance (ESR) spectra were measured at 6 K in single crystals of CuAlS 2 doped with Mo. A fine-structure PL emission was observed around 1,600 nm (0.775 eV). The emission was assigned to the ligand-field transition in 4d 3 -manifold of Mo 3+ ions. The ESR spectrum measured in the same crystal as used in the PL experiment showed a triplet structure around g ∼2, which is characteristic of S=3/2 system. The activation energy of the temperature quenching of the ESR intensity was 4 meV, which is the same as that of the emission, suggesting that the ESR and the PL spectra originate from the same center.