Pseudo-dielectric functions, band-to-band transitions, and dielectric-related factors in a single-crystal LiTi2O4 thin film.

This article is devoted to studying the optical properties of a novel single-crystal LiTi 2 O 4 thin film. A high-quality (011)-oriented LiTi 2 O 4 single-crystal thin film was prepared on a MgAl 2 O 4 (011) substrate by pulsed laser deposition. The weak in-plane optical anisotropy is discovered by Mueller-matrix spectroscopic ellipsometry, which can be attributed to the cooperative Jahn-Teller distortion in the Ti–O octahedrons. The pseudo-dielectric functions were determined in the photon energy of 1.24–5.06 eV using the ellipsometric spectra. The optical conductivity, plasma frequency, effective mass, scattering time and other dielectric-related factors are also discussed. The critical points obtained in the pseudo-dielectric functions are originated from the charge-transfer transitions of the Ti related pairs. The results demonstrate that the enhanced effective mass is responsible for the high optical transparency of LiTi 2 O 4 rather than the large high frequency dielectric constant ε ∞. • The weak in-plane optical anisotropy was first observed by MMSE. • The optical transitions in LTO are originated from charge transfer transitions of Ti related pairs or isolated Ti ions. • The optical transparency of LTO is dominantly originated from the enhanced effective mass rather than large ε ∞ . [ABSTRACT FROM AUTHOR]