The Gas Sensing Properties Of Two-dimensional SnSe₂ And Its Heterojunction Semiconductors

Nitrogen dioxide?NO₂?acts a critical part in the industrial,aerospace and other fields,but also a common pollutant gas.Short-term exposure in 1 ppm concentration of NO₂ can be harmful to lung health.Long-term exposure in the excessive NO₂ environment will suffer from lung disease.Therefore,when there are interfering gases,it's extremely important to develop a sensor that can accurately,reliably and quickly detect low concentrations of NO₂ in the environment to protect human health protection and detect air quality.However,the current selection of NO₂ sensor may be a tradeoff with its sensitivity,reproducibility and manufacturing cost.Currently,SnO₂ has a solid research foundation in NO₂ detection and shows a good response,but the optimum temperature is higher than 200°C.Sn S2,which is in the chalcogenide tin compound family with SnO₂,has become a research hotspot in recent years.Sn S2 has an excellent response and the optimum temperature is reduced to 120°C.In order to prepare the NO₂ sensor to work at low temperature,SnSe₂ material is selected in this paper,which is in the same group as SnO₂,Sn S2 and has a larger atomic radius.SnSe₂ is analyzed by TGA,SEM,EDS,TEM and XRD.The gas sensing properties are tested,such as sensitivity,selectivity,response/recovery time and optimal operating temperature.The results show that the SnSe₂ sensor shows a good response to NO₂ gas at room temperature,but also has a response to NH3.In order to improve the selectivity of SnSe₂ to NO₂,the SnSe₂/SnO₂ heterojunctions are prepared with thermal oxidation method by in-situ oxidation of flake SnSe₂,and then characterized and tested the gas sensing performance.The results show that the SnSe₂/SnO₂ heterojunction formed by thermal oxidation at 500°C for 1h has the best gas sensing performance.Compared with pure SnSe₂,the response of SnSe₂/SnO₂ heterojunction to NO₂ has been greatly improved,and it has an excellent selectivity to several common VOC gases including NH3.This paper also analyzes the mechanism of the results,the formed heterojunctions produce the electron depletion layer,which promotes the electron transfer to attract more chemisorbed oxygen,and the formed SnO₂ generates more vacancies to facilitate gas adsorption,thereby the gas sensing properties are effectively improved.In summary,the SnSe₂ microflakes based chemiresistive-type sensors show a good response to NO₂ at room temperature and excellent reversibility.SnSe₂/SnO₂ heterojunctions generated by thermal oxidation represent an excellent performance to NO₂.