Robust Material Properties in Epitaxial In ₂ Te ₃ Thin Films across Varying Thicknesses

Sesqui-chalcogenides serve as a critical bridge between traditional semiconductors and quantum materials, offering significant potential in applications such as thermoelectrics, phase change memory, and topological insulators. While considerable attention has been focused on antimony- and bismuth-based compounds, characterized by substantial property changes upon reduction in film thickness, indium-containing sesqui-chalcogenides like In₂Te₃ are emerging as promising candidates for photovoltaics and electronic devices. However, the effects of film thickness on the properties of In₂Te₃ remain largely unexplored. In this study, we investigate high-quality In₂Te₃ thin films grown by molecular beam epitaxy on Si(111) substrates across a thickness range from 2.7 to 24 nm. X-ray diffraction, reflective high-energy electron diffraction, and atomic force microscopy are employed to analyze both the crystal structure and film morphology. Additionally, broadband optical spectroscopy alongside femtosecond pump-probe measurements and Raman spectroscopy are utilized to assess optical and vibrational properties, respectively. This analysis reveals that material properties exhibit minimal dependence on film thickness - contrasting sharply with behavior observed in other chalcogenides such as Sb₂Te₃, Bi₂Se₃, or GeTe. This phenomenon can be attributed to the covalent bonding present in In₂Te₃, which differs from that in its antimony- and bismuth-containing counterparts.