Space-Resolved Spectra Due to Highly Mobile Excition at the Stacking Fault in BiI3Crystals

Abstract

The study of exciton transfer along the stacking fault interface in BiI 3 crystals is presented by using a newly designed space-resolved spectroseopy method. The resonant luminescence lines of the excitons with exact zero Stokes shift were observed in the space-resolved spectra at a point of more than 300 µm away from the exciting laser spot. Analyzing the spatial distribution of the resonant luminescence intensities on the assumption of exciton diffusion, we obtained unusually large diffusion coefficients of more than 10 5 cm 2 /sec at 4.2 K. This result indicates the existence of highly mobile excitons. The spatial distribution of the resonant luminescence intensities becomes smaller with decreasing temperature. The temperature dependence is discussed based on the weakly bound exciton model.