Investigation Of Temperature-Dependent Hard X-Ray Photoemission Spectra On Au/Nb:Srtio3 Schottky Junctions

With the temperature and electric field dependence of the dielectric permittivity of Schottky junctions, conventional methods cannot fully capture the properties of the junctions. Hard X-ray photoemission spectroscopy (HAXPES) has been used in characterizing device stack structures. In this study, HAXPES was employed to investigate the temperature dependence of the electronic band structures at Schottky junctions composed of Au and niobium-doped n-type strontium titanate (Nb:SrTiO3). The Au/Nb:SrTiO3 Schottky junctions were formed by magnetron sputtering. HAXPES revealed the band-bending profiles at the junctions. The core-level spectra of the buried Nb:SrTiO3 showed peak broadening and a shift, indicating the formation of a potential barrier at the interfaces. The temperature dependence of these spectral features, along with the hysteresis loops observed in the current-voltage characteristics, changed significantly as temperature decreased, indicating the reduction of the Schottky barrier width with decreasing temperature. The simulated HAXPES profiles deduced from the calculated potential distribution were consistent with the observed HAXPES profiles. However, comparison of both temperature-dependent HAXPES profiles indicates the conventional phenomenological model is not completely appropriate and the importance to reassess it for the dielectric permittivity of Nb:SrTiO3 at low temperatures under a high electric field.