Concentration Effects on Characteristics of Gas Sensors Based on SnO<sub>2</sub>:Sb<sub>2</sub>O<sub>3</sub> Thin Films

Abstract

In this research, SnO2 nanostructure thin films were fabricated by spray pyrolysis method, using concentration of tin (Sn) salt solution deposited on a glass substrate at temperature of 450 °C. The tin solution was prepared by solves 2.2563gm of SnCl2.2H2O (molecular weight 219.4954 g/mole) in 100 ml of ethanol, then add 60 drops of pure hydrochloric acid ( HCl) using drop by drop technique. Different concentrations of antimony oxide (1%, 2%, 3%, 4%) hve been used to depose the thin films. The structure has been examined by X-ray diffraction technique, which shown that all films are polycrystalline with tetragonal rutile crystalline structure with preferential orientation in the (200) direction and, grain size decreases with increasing doping concentration. Optical measurements shown that the films are transparently in the visible region, with an average transmittance more then 80% and, sharp absorption edge nearly at 350 nm, the nature of the optical transition were direct allowed with band gap varies between (2.97 - 3.75 eV) which is directly proportional to doping concentration. The results also show that the doping has led to improved the response time of the sensing. Two kinds of gases NO2 and NH3 have been used to test the sensing performance, at different operating temperatures (R.T, 100, 200, 250, 300 and 350) oC , and bias voltage (3 Volt). For NO2 gas the highest sensitivity was 77%, the shortest response time 2.9 s and the recovery time 19 s, while for NH3 gas sensitivity was 11.5%, the response time 4.1 s and the shortest recovery time 20s,