Probing phononic behavior of 40nm TbInO3 films using Raman Scattering Spectroscopy

TbInO₃ shows Mott insulator behavior at room temperatures and an absence of magnetic order down to 0.46K(Clark et al., 2019). Thin films of TbInO₃ allow large surfaces and possible tuning of properties with strain from a substrate. Raman spectroscopy is a popular characterization method, but measurements of thin films have been difficult due to low signals and complex film-substrate spectral overlap. In this work we demonstrate a method to detect Raman scattering of thin films, using a 40nm film of TbInO₃ on a YSZ substrate.

We obtain a reliable Raman response of the TbInO₃ film in pseudo-Brewster geometry. We further test the response dependence on excitation laser wavelength and incoming angle of excitation light. We compare the film response to that of TbInO₃ in bulk crystal form. While the phonons related to the E1g motion of the Oxygens in the base of InO6 octahedra are comparable between film and bulk, the out-of-plane motion of Oxygens and Tb shows lower intensity and higher damping. On temperature decrease down to 10K, film signal decreases and disappears, suggesting that electronic screening of the film signal increases at low temperatures.