Temperature-dependent phonon mode and interband electronic transition evolutions of ϵ -InSe films derived by pulsed laser deposition

We report the temperature-dependent phonon modes and interband electronic transitions of InSe films on SiO2/Si substrates prepared by pulsed laser deposition. The microstructure results proved the ϵ phase structure and monochalcogenide phase composition with well-defined hexagonal InSe sheets. The temperature effects on lattice vibrations were discovered by Raman spectra from 123 K to 423 K. The frequency and full width at half maximum of the A 2 g 1(LO) mode show a strong nonlinearity with the temperature. The energy band structure and electron-phonon interaction were studied by temperature-dependent spectroscopic ellipsometry with the aid of the Tauc-Lorentz model. It was found that five electronic transitions around 1.33, 1.61, 2.53, 3.73, and 4.64 eV generally show a redshift trend with the temperature. The present results can provide a valuable reference for future optoelectronic applications of InSe films.