Sensing Properties of Lateral Graphene/h-BN Heterostructure towards NH3: A First Principles Study

Adsorption of NH3 molecule on graphene/hexagonal boron nitride heterostructure (G/h-BN) was investigated by applying density functional theory. Structural, electronic and adsorption properties of this heterostructure towards NH3 are reported. The N site at G/h-BN interface has been shown to have the highest adsorption energy and the amount of adsorption energy indicates a physical adsorption. Despite the weak interaction between the molecules and the surface, a measurable signal for sensing applications can be expected due to the sensitivity of tunneling current to the changes in electronic structure. Our results show that the proposed device could have a higher sensitivity comparing to the pristine graphene and pure h-BN.

I. Introduction

Toxic gasses which derived from industries and automobiles are harmful for human health, ozone layer and global climates. Therefore, gas sensors are crucial for the detection of toxic gasses. Semiconductor based gas sensors attract enormous attention due to their excellent stability and surface reactivity in ambient conditions. One of the challenges of semiconductor-based gas sensors is to meet the demands for higher sensitivity and selectivity. Among different semiconductors, metal oxides based sensors show a quite well performance; nevertheless, some of them are harmful to the environment [1]. The 2D semiconductor materials with their large surface to volume ratio and unique optical and electrical properties are promising candidates for gas sensing applications [1], [2]. Graphene nanoribbons (GNRs) with honeycomb lattice structure show few advantages in sensing applications comparing to carbon-nanotubes (CNT) and silicon-nanowires (SiNW). GNR has excellent performance owing to high surface to volume ratio which increases the adsorption sites for gas molecules. Moreover, GNRs have very high electron and hole mobility even at room temperature based on their unique structure [3].