Schottky Nature of Au/SnO 2 Ultrathin Film Diode Fabricated Using Sol–Gel Process

In this letter, sol–gel-processed SnO 2 films were deposited, with thicknesses varying from 3.5 to 5.0 nm, by controlling the concentration of the precursor solutions. Through electrical and spectroscopic investigations, it was found that the optical energy bandgap and the electron affinity were affected by the quantum confinement effect and Burstein–Moss effect. Moreover, the increased barrier height between Au and SnO 2 semiconductors was enhanced when thinner SnO 2 layers were used, resulting in strong Schottky diode characteristics. This letter allows one to examine the size scaling effects of ultrathin electrical devices with SnO 2 channel layers. In addition, a generalized energy band diagram derived from the bandgap broadening in ultrathin SnO 2 semiconductors is presented, which will allow the elucidation of the carrier transport mechanism and optical properties of quantum confined SnO 2 semiconductor-based optical and electrical devices.