Phosphorene as a Superior Gas Sensor: Selective Adsorption and Distinct <i>I</i>–<i>V</i> Response

TLDR

Phosphorene, a mono‑ or few‑layer black phosphorus, is a promising 2D material with excellent properties for nanodevice applications. The study uses first‑principles calculations to investigate adsorption of CO, CO₂, NH₃, NO, and NO₂ on monolayer phosphorene. We determine optimal adsorption sites, identify charge transfer as the key mechanism for strong adsorption, and compute I‑V characteristics via NEGF. Phosphorene shows superior gas‑sensing performance, with highly anisotropic I‑V responses that vary distinctly for different gases, indicating strong selectivity and sensitivity.

Abstract

Recent reports on the fabrication of phosphorene, that is, mono- or few-layer black phosphorus, have raised exciting prospects of an outstanding two-dimensional (2D) material that exhibits excellent properties for nanodevice applications. Here, we study by first-principles calculations the adsorption of CO, CO2, NH3, NO, and NO2 gas molecules on a monolayer phosphorene. Our results predict superior sensing performance of phosphorene that rivals or even surpasses that of other 2D materials such as graphene and MoS2. We determine the optimal adsorption positions of these molecules on the phosphorene and identify molecular doping, that is, charge transfer between the molecules and phosphorene, as the driving mechanism for the high adsorption strength. We further calculated the current-voltage (I-V) relation using the nonequilibrium Green's function (NEGF) formalism. The transport features show large (1-2 orders of magnitude) anisotropy along different (armchair or zigzag) directions, which is consistent with the anisotropic electronic band structure of phosphorene. Remarkably, the I-V relation exhibits distinct responses with a marked change of the I-V relation along either the armchair or the zigzag directions depending on the type of molecules. Such selectivity and sensitivity to adsorption makes phosphorene a superior gas sensor that promises wide-ranging applications.