Layered SnSe2 microflakes and SnSe2/SnO2 heterojunctions for low-temperature chemiresistive-type gas sensing

Abstract

Layered SnSe₂ flakes and SnSe₂/SnO₂ heterojunction-based chemiresistive-type sensors demonstrate good gas sensing properties at low temperatures. The pure SnSe₂-based chemiresistive-type sensor exhibited good response and recovery to both NO₂ and NH₃ while also showing a moderate response to hydrogen, CO, C₃H₆ and several typical volatile organic vapors, such as methanol, ethanol, acetone and formaldehyde, near room temperature, indicating that it possesses poor selectivity. However, compared to pristine SnSe₂, a SnSe₂/SnO₂ heterojunction-based chemiresistive-type sensor prepared by the thermal oxidation method showed greatly improved sensitivity and superior selectivity toward NO₂ at 120 °C. Such impressive improvements in the sensing performance can be attributed to the formation of SnSe₂/SnO₂ heterojunctions. The density functional theory (DFT) calculations revealed that there was a lower adsorption energy and greater Bader charge value between the adsorbed NO₂ and SnSe₂/SnO₂ heterojunction materials.