Quantum size and composition effects in photoacoustic spectra of FexZr1−xO2 clusters

Abstract

The quantum size and composition effects on the optical properties of FexZr1−xO2 (x=0, 7.5, 15, and 35 wt %, respectively) clusters were studied by measuring their photoacoustic spectra at room temperature. We observed a concomitant smearing of the band gap, narrowing the effective gap of the grains with increasing iron content. These phenomena are attributed partly to the formation of a separate Fe2O3 phase, likely residing at the grain boundaries. The appearance of five spectral bands may be ascribed to the electronic transition of the Fe3+ centers in the samples from the ground level to five excitation states. The exciton peaks occur and shift towards blue, which can be explained by the quantum size effect. The absorption edges exhibit a red shift with increasing Fe content due to the Burstein’s effect.