Electronic and Optoelectronic Properties of Heavy Metal-Adsorbed h-BAs Monolayer: A DFT-Based Sensor Study

Detection of heavy metals in water and air is imperative for a clean environment and assuring human health. In this study, we explore the potential of a twodimensional (2D) hexagonal boron arsenide (h-BAs) monolayer as a highly effective sensing material for key heavy metals, like lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), nickel $(\text{Ni})$, antimony (Sb), and selenium (Se). Through state-of-theart density functional theory, the study evaluates key sensing properties of these metals: formation and adsorption energies, bandgap, electrical conductivity, and absorption coefficient on the $h$-BAs monolayer and its two terminal I-V characteristics. Notably, this study examines, negative differential resistance (NDR) which is observed in the $I-V$ characteristics of heavy metal-adsorbed h-BAs at higher voltages ($1.75 \mathrm{V}-2 \mathrm{V}$), marking a significant advancement for sensing applications. For a more realistic simulation, the study also considers the adsorption of heavy metals in the presence of water molecules, which lowers the threshold voltage. The study shows the high potential of $h$ BAs 2D material for key heavy metal detection.