Adsorption and gas-sensing performance of sulfur gases on SnS/GeSe heterojunction

Abstract

This article uses first principles calculations to study the electronic transport properties of two-dimensional materials germanium selenide (GeSe), tin sulfide (SnS), and their SnS/GeSe van der Waals heterostructures for adsorbing three sulfur gases. Through total energy calculations, we determined that H₂S and SO₂ tend to adsorb more readily to the vacancies on the surfaces of GeSe, SnS, and the SnS/GeSe heterojunctions, whereas SO₃ shows a stronger preference for adsorbing to the top sites. By analyzing the band structure of sulfur gases after adsorption, we found that H₂S adsorption has no regulatory effect on the electronic structure of monolayers and heterojunctions, but the adsorption of SO₂ and SO₃ can regulate the electronic structure of monolayers and heterojunctions to varying degrees. Among them, the adsorption of SO₂ most significantly modulates the band structure, not only adjusting the position of energy distribution within the band structure but also inducing new energy band. Therefore, we constructed a gas sensing device based on SnS/GeSe heterojunction and focused on studying the electronic transport properties before and after SO₂ adsorption. The device without gas adsorption consistently exhibit very small currents within the bias voltage range of −0.7 V to 0.7 V. However, the adsorption of SO₂ notably enhances the current of the device and displays a negative differential resistance effect in both positive and negative bias region, with a peak-to-valley ratio approaching 300. Therefore, we conclude that SnS/GeSe heterojunction devices can serve as gas sensitive adsorption detection devices for SO₂, which has important physical significance for further understanding the electronic transport mechanism of molecular devices.