A novel hetero-structure sensor based on Au/Mg-doped TiO^sub 2^/SnO^sub 2^ nanosheets directly grown on Al^sub 2^O^sub 3^ ceramic tubes

Chemiresistive gas sensors with novel nanostructures, high response and reliable fabrication process have been fabricated successfully by designing Au/Mg-doped TiO2/SnO2 nanosheets hetero-structures. Mg doping was used to decrease the work function of TiO2, which can lead to the electrons in TiO2 greatly depleted due to the formation of Schottky contact and n-n heterojunction. SnO2 nanosheets were directly grown on Al2O3 tube with a cost-effective hydrothermal process. By employing pulsed laser deposition (PLD) and direct current sputtering methods, the construction of gold (Au) nanoparticles-loaded Mg-doped TiO2/SnO2 heterostructure is highly controllable and reproducible. In comparison with pristine SnO2 and TiO2/SnO2, Mg-doped TiO2/SnO2 sensors exhibit high response (30.4) and short response time (9 s) to 50 ppm TEA gas, which is about 6 times higher than pure SnO2 sensor and 2 times higher than TiO2/SnO2 sensor at a working temperature of 260 °C. The mechanism for sensing property enhancing of the Au/Mg-doped TiO2/SnO2 sensor was also discussed in detail with the semiconductor depletion layer model introduced by Au-TiO2 Schottky contact and TiO2/SnO2n-n heterojunction.