Synthesis of SnO2-x thin films by oxygen-ion-assisted deposition for hydrocarbon gas detection

Abstract

With the aim of developing efficient microsensors with low power consumption for the detection of inflammable hydrocarbon gases (CH4, C3H8), SnO2 thin films were synthesized and their gas sensing properties tested. Using an oxygen-ion-assisted deposition technique, a series of SnO2 thin films with various crystalline structures and nonstoichiometry were prepared as a function of oxygen ion energy. The material properties of the synthesized thin films were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) and the sensing properties were determined based on the measurements of electrical conductance in a test gas environment. The as-deposited tin oxide thin films were observed in an amorphous state and the annealed films showed a preferred orientation to the <110> axis, along with <101> and <211>. All the deposited films showed a deficiency in oxygen content as the state of SnO2-x but had a binding energy of Sn+4. With regard to differentiation in the sensitivities and selectivities of methane and propane, the effective factors were determined to be substrates (SiO2/Si, alumina), electrode position, amount of dopants (Pt, Pd) and ion beam energy.