Low-temperature NIR-VUV optical constants of (001) LaAlO3 crystal

The optical constants and dielectric function of (001) LaAlO3 crystalwere investigated at low temperatures down to 10K in the NIR-VUV spectral range (photon energies 0.8-8.8 eV). Reflection variable angle spectroscopic ellipsometry and transmission spectroscopy were applied. Interband transitions were examined using the Tauc plots and the critical-point analysis. At room temperature, the indirect bandgap of 5.6 +/- 0.01 eV and the lowest-energy direct transition at 7.2 +/- 0.03 eV were detected. On cooling to 10 K, a blueshift of similar to 0.2 eV and similar to 0.1 eV was observed for the indirect and direct transitions, respectively. In the transparency spectral range, the index of refraction was found to be nearly temperature-independent and vary with photon energy from 2.0 (1 eV) to 2.5 (5.5 eV). It was suggested that the excellent thermal stability of the index of refraction may be related to the revealed thermally stable interband transitions. The results are of importance for modeling and design of modern optical devices. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

The optical constants and dielectric function of (001) LaAlO3 crystal were investigated at low temperatures, revealing the bandgap and transition properties at different temperatures. The study also found that the refractive index exhibits excellent thermal stability.