Asymmetric functionalization as a promising route to open the band gap of silicene: A theoretical prediction

Abstract

Recent studies have suggested that chemical functionalization is a promising avenue to tailor the band gap of silicene, which plays an important role on widening its application. Here, we propose a new route to functionalize silicene, that is asymmetrically modification of silicene (Janus silicene or X–silicene–Y), which is produced by co-grafting of two different groups (X and Y) on both sides of silicene. By performing density functional theory (DFT) calculations, we demonstrate the stability and electronic properties of X–silicene–Y sheets. The results indicate that chemical functionalization on one side can greatly enhance the chemical reactivity of the opposite side, suggesting the communication between the two adsorbed groups and enhancing the stability of the hybrids. Compared to the pristine silicene with a zero band gap, X–silicene–Y sheets exhibit semiconducting nature with a non-zero band gap, which is dependent on the coverage of X/Y. Our results provide a novel and effective method to engineer the band gap of silicene, which would be useful to design novel silicene-based devices with multiple functions.