Structural, optical and NO2 gas sensing properties of ZnMgO thin films prepared by the sol gel method

In this present work, ZnO and ZnMgO thin films prepared by a sol-gel process were deposited on glass substrates via spin coating technique. The structural, morphological and optical properties of the obtained films were investigated. X-ray diffraction study revealed that all layers exhibit a hexagonal wurtzite structure without any secondary phase segregation. The atomic force microscopy (AFM) depicts that the grains size of ours samples decreases as magnesium content increases. The absorption spectra obtained on ZnMgO thin films show a band gap tuning from 3.19 to 3.36 eV, which is also consistent with blue shifting of near-band edge PL emission, measured at low temperature. The incorporated amount of magnesium was calculated and confirmed by EDX. The gas sensing performances were tested in air containing NO2 for different operating temperatures. The experimental result exhibited that ZnMgO sensors shows a faster response and recovery time than the ZnO thin films. The resistivity and the sensor response as function of Mg content were also investigated.