Micro-mechanism study of charge transfer at heterojunction interface based on first-principles theory: MoS₂/SnO₂ as the prototype

Gas sensors made of semiconductor heterojunctions have excellent gas-sensitive properties. However, sufficient theoretical evidence is still needed to prove that heterojunction improve gas sensitivity of a single-material. A typical case is studied here: MoS₂/SnO₂ heterojunction absorption of NO₂ is investigated by first-principles calculations, to explore the enhancing-mechanism. Interestingly, it is found that electron transfer not only occurs between the material surface of the heterojunction and gas, but also involves the substrate atoms transferring electrons to the gas molecules through the surface atoms. This finding fills the response mechanism of heterojunction gas sensors and provides a theoretical basis for experiments.