Photoreflectance spectroscopy of BiOCl epitaxial thin films

• Published in: Japanese Journal of Applied Physics Vol. 63; no. 2; pp. 2 - 6
• Main Authors: Nishiwaki, T., Sun, Z., Oka, D., Fukumura, T., Makino, T.
• Format: Journal Article
• Language: English
• Published: Tokyo IOP Publishing 29-02-2024; Japanese Journal of Applied Physics
• Subjects: Critical point; dielectric functions; electronic structures; excitons; Line shape; Line spectra; Optical transition; spectroscopy; Substrates; Thin films
• ISSN: 0021-4922; 1347-4065
• DOI: 10.35848/1347-4065/ad0306

Abstract
We have observed a new optical transition in the photoreflectance spectra of indirect-gap BiOCl thin films, which were grown on SrTiO
3
substrates. The position of this transition is close in energy to its bulk critical point (CP) energy. Moreover, these are significantly lower than a higher-lying direct-type CP from an energetic point of view. The spectral line shape analysis for our observed signal suggests the presence of an excitonic effect of this compound. We determined its dependence of the optical anomaly on temperature ranging from 80 K to RT. We adopted the Varshni model for this analysis. At last, we compared photonic properties of BiOCl with those of an element and binary semiconductors.