Two-dimensional Janus X2STe (X = B, Al) monolayers: the effect of surface selectivity and adsorption of small gas molecules on electronic and optical properties

Abstract

This investigation delves into the adsorption characteristics of CO, NO, NO₂, NH₃, and O₂ on two-dimensional (2D) Janus group-III materials, specifically Al₂XY and B₂XY. The examination covers adsorption energies and heights, diverse adsorption sites, and molecular orientations. Employing first-principles analysis, a comprehensive assessment of structural, electronic, and optical properties is conducted. The findings highlight NO₂ as a prominent adsorbate, emphasizing the Te surface of 2D Al₂STe and B₂STe materials as particularly adept for NO₂ detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the B₂STe material. The adsorption properties of all gas molecules, except for NO₂, on both materials were determined to be physical. Upon adsorption of the NO₂ gas molecule onto the B₂STe Janus material, it was observed that the material exhibited weak chemical adsorption behavior, which was confirmed by the adsorption energy, larger band gap change, electron localization function, work function changes and charge transfer from the material. This research provides valuable insights into the gas-sensing potential of 2D Janus materials.