N-type and P-type SnO_x thin films based MOX gas sensor testing

In this article, n-type and p-type SnO_x thin films are deposited using the same precursor with a simple chemical method of spray pyrolysis on the top of the fabricated MOX gas sensor at T = 350 ℃ and 500 ℃ respectively, without any post-deposition annealing step. The deposited films were investigated using the following characterization methods. X-ray diffraction revealed that the deposited n-type SnO₂ thin films have a tetragonal rutile structure and in p-type SnO we identified two phases, a tetragonal SnO and orthorhombic SnO. Atomic force microscopy (AFM) indicates that films are homogenous and uniform within a scanned area of 334 nm with a small grain size of 10–15 nm. The performance of the fabricated sensors was performed by electrical characterization and sensing behavior under different concentrations of ethanol C = 7000 ppm, 3500 ppm, 1200 ppm, 600 ppm, and 300 ppm, at an operating temperature T_op = 250 ℃ and RH 50%. The evolution under gases showed a higher response for p-type SnO as compared to n-type SnO₂.