X-ray photoelectron spectroscopy study and humidity sensing properties of Zn doped SnO2 thin films

Abstract

Undoped and Zn-doped SnO2 thin films are deposited onto glass substrates by sol–gel spin coating method. All the films are characterized by X-ray photon spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR). XPS shows that Sn presence as valence of Sn4+ in the prepared SnO2 thin films instead of Sn2+. In addition, it also exhibits the amount of Zn in SnO2 thin films, which increases with increasing Zn doping percentage. The Zn (2P3/2) peak is symmetric and centred at around 1,021.73 eV which shifts to the lower binding energy of 1,020.83 eV for 15 at.% Zn doped SnO2 thin film. FTIR study is used to describe the local environment of undoped and Zn-doped SnO2 thin films which also confirms the synthesis of undoped and Zn-doped SnO2 thin films. It is found that the resistance of SnO2 thin films increases as Zn doping concentration increases at room humidity. The resistance of all the samples increases as relative humidity (RH) increases. The sensitivity of SnO2 thin films increases as RH increases while it decreases as Zn doping percentage increases. Response time of SnO2 thin film decreases as Zn doping percentage increases and recovery time slightly increases with doping percentage.