Ti-Doped Graphene/Hexagonal Boron Nitride Heterostructures for Advanced Gas Detection: A DFT Study

Two-dimensional (2-D) materials have emerged as promising candidates for detecting harmful gases due to their high surface-to-volume ratio and fantastic physical characteristics. However, their stability and low reactivity in pure form necessitate surface modifications to enhance interactions with toxic gases. This study introduces a novel Ti-doped G/h-BN/G heterostructure for gas sensing. The h-BN layer, positioned between graphene layers, anchors the Ti atom and enhances sensitivity by inducing quantum tunneling current within the channel. The stability of Ti dopant at different vacancies in the h-BN region, its influence on the electronic structure, as well as the interaction with five distinct toxic gases (NO2, CO, NH3, HCN, H2O), are investigated by employing Density Functional Theory (DFT) and non-equilibrium Green’s function (NEGF) formalisms. Ti doping at B-vacancy (Ti/VB) and Stone-wales defect (Ti/VB+N) sites are found to be highly stable, demonstrating favorable electrical and physical properties for gas detection. The Ti-doped devices show stronger gas adsorption compared to pure devices, leading to enhanced interactions and a greater impact on current flow. Specifically, Ti/VB exhibits higher sensitivity to NO2 and HCN gases, while Ti/VB+N is more suitable for distinguishing CO and NH3 gas molecules. Additionally, interaction with H2O indicates that these structures are capable of operating in humid environments. Therefore, the proposed Ti-doped G/h-BN/G heterostructure is a promising compound for developing accurate and reliable toxic gas detectors.