Electrical and Optical Properties of Germanene on Single-Layer BeO Substrate

A comprehensive first-principles study has been employed to investigate the geometric structures, electrical properties, and optical properties of two-dimensional (2D) Ge/BeO heterostructure. The results show that there is weak interaction between germanene and BeO monolayer via van der Waals force without any site selectivity. Therefore, most of the outstanding properties of germanene are conserved, especially a linear band dispersion near the K point. The energy gap of similar to 49 meV can be opened for the heterostructure, which is a pretty large value for the gap opening at room temperature. Meanwhile, the band gap can be tuned by the interlayer distance, external strain, as well as external electric field, and the electric field has been found to be the most effective way (14-382 meV). All of these methods for band gap modulation can maintain the characteristics of a Dirac cone with a linear band dispersion relationship of germanene. Moreover, the enhanced optical properties are also observed after the formation of the heterobilayer system. In general, the calculated results indicate that the Ge/BeO heterostructure holds great potential in electrical and optoelectronic applications. BeO monolayer, an excellent candidate of germanene substrate, can attract more attentions in substrate materials research.