Barrier heights at the SnO2/Pt interface: In situ photoemission and electrical properties

The SnO2/Pt contact has been investigated using in situ photoelectron spectroscopy and electrical 2-point and 4-point conductivity measurements. A remarkable increase of barrier height from 0.4 eV to 0.9 eV is observed after annealing the as-deposited contact in 0.5 Pa oxygen atmosphere. Subsequent annealing in vacuum reduces the barrier height again. Despite the expected large barrier height, the current-voltage characteristics displays ohmic behavior. The discrepancy between photoemission and electrical behavior is attributed to the polycrystalline nature of the SnO2 film used in this study, leading to an inhomogeneous Schottky barrier height along the surface of polycrystalline specimens.