Effect of resonant tunneling modulation on ZnO/In2O3 heterojunction nanocomposite in efficient detection of NO2 gas at room temperature

The unique multiple barrier characteristics of heterojunctions significantly change the electrical and optical properties of semiconductor composites, and also affect the temperature and response rate of gas-sensitive detection. In this paper, the as-obtained ZnO/In2O3 nanocomposites achieve rapid detection of ppb-level NO2 gas at room temperature through resonance tunneling modulation. The ZnO nanosheets loaded with In2O3 nanoparticles are successfully prepared using ultrasonic chemical reaction and high temperature annealing method. The crystal structure analysis shows the unique heterostructure of In-O-Zn is formed between the (104) plane of In2O3 nanoparticles and the (002) plane of ZnO nanosheets. The gas-sensitivity study shows that the ZnO/In2O3 heterojunctions have good selectivity and low detection limit to NO2 gas at room temperature when exposed to a laser. When the NO2 gas concentration is 10 ppm, the response and recovery times are 61 s and 39 s, respectively. The mechanism analysis shows that the laser irradiation causes the carrier resonance tunneling transport, achieving the highly sensitive detection of NO2 gas at room temperature. The resonance tunneling modulation process of composite heterojunctions has the characteristics of fast response and recovery speed. Thus the as-obtained ZnO/In2O3 heterojunctions is an ideal material for gas detection at room temperature.