Dimensionally driven crossover from semimetal to direct semiconductor in layered SbAs

Two-dimensional (2D) materials have attracted a great deal of attention because they exhibit intriguing physical and chemical properties with great potential applications in electronic and optoelectronic devices, and even energy conversion. Due to the high anisotropy and unique crystal structure of layered materials, the properties can be effectively tuned by simply reducing dimensions to 2D. In this work, a unique 2D semiconductor, namely, monolayered SbAs, with high stability and indirect band gap, is predicted on the basis of first-principles calculations together with cluster expansion and Monte Carlo simulations. Interestingly, although the bulk antimony arsenide compound SbAs is known to exhibit semimetallic behavior, our calculations find that it is transformed into a direct semiconductor with a band gap of 1.28 eV when thinned down to a single atomic layer. The monolayer with antisite defects is transformed from indirect into a direct band-gap semiconductor. Such dramatic changes in the electronic structure could pave the way for SbAs to play a role in electronic device applications. Moreover, we find that the interlayer interactions in SbAs lead to a higher exfoliation energy than typical transition metal dichalcogenides such as MoS2, and hence we suggest that chemical deposition methods might be better than mechanical exfoliation methods for obtaining monolayer samples.