Temperature Dependence of Surface Band Bending in Layered BiTeI Semiconductor

The band bending effect at the surfaces of layered semiconducting materials is crucial for the overall performance of thermoelectric devices. However, a study dedicated to investigating the temperature dependence of the band bending effect in layered semiconductors has yet to be reported. The BiTeI semiconductor is a representative layered thermoelectric material, and this study directly investigated its electronic band structure as a function of temperature by utilizing photon-energy-dependent angle-resolved photoemission spectroscopy. The surface terminations of the crystal that we used were found to consist mainly of tellurium atoms. Additionally, the binding energies of the surface band increased by approximately 40 meV as the temperature rose from 10 to 100 K, which can be ascribed to the suppression of the electron transport process from the BiTeI surface to its bulk by phonon and defect. Our findings clearly provide direct evidence of temperature-dependent band bending in BiTeI.