Fabrication of highly c-axis Mg doped ZnO on c-cut sapphire substrate by rf sputtering for hydrogen sensing

Mg:ZnO films which are highly c-axis oriented were deposited on Al₂O₃ substrate by radio frequency sputtering for different substrate temperatures. It is observed from the crystal structure that the Mg dopants are well interspersed into ZnO wurtzite lattice. The substrate temperature shows remarkable impact on the luminescence properties, optical absorbance, bandgap and morphological properties of Mg:ZnO films. The surface topography of Mg doped ZnO film confirmed increased grain size with significant surface roughness and increased surface area, favorable for sensing. The Mg:ZnO/Al₂O₃ films fabricated at various temperature were examined for its sensing ability at 200 ppm of H₂ at room temperature. The response and recovery time of Mg:ZnO sensor at 1400 °C are about 75 and 54 s, respectively. In the limit of 100–700 ppm, the sensor remained undeviated to the concentration of H₂. It can be summarized that this significant performance of H₂ sensor has potential for use as a portable room temperature gas sensor.