Tunable electronic structures of germanane/antimonene van der Waals heterostructures using an external electric field and normal strain

oscale devices.In the present work,we investigate the electronic structures of germanane/antimonene vdW heterostructure in response to normal strain and an external electric field by using the first-principles calculations based on density functional theory(DFT).The results demonstrate that the germanane/antimonene vdW heterostructure behaves as a metal in a[1,,0.6]V/A range,while it is a direct semiconductor in a[0.5,0.2]V/A range,and it is an indirect semiconduc-tor in a[0.3,1.0]V/A range.Interestingly,the band alignment of germanane/antimonene vdW heterostructure appears astype-II feature both in a[0.5,0.1]range and in a[0.3,1]V/A range,while it shows the type-I character at 0.2 V/A.In ad-dition,we find that the germanane/antimonene vdW heterostructure is an indirect semiconductor both in an in-plane biaxial strain range of[[5%,,3%]and in an in-plane biaxial strain range of[3%,5%],while it exhibits a direct semiconductor character in an in-plane biaxial strain range of[2%,2%].Furthermore,the band alignment of the germanane/antimonene vdW heterostructure changes from type-II to type-I at an in-plane biaxial strain of 3%.The adjustable electronic structure of this germanane/antimonene vdW heterostructure will pave the way for developing the nanoscale devices.

First-Principle Studies on the Ga and As Doping of Germanane Monolayer

The study of energetics, structural, the electronic and optical properties of Ga and As atoms substituted for doped germanane monolayers were studied by first-principles calculations based on density functional theory. Both of the two doping are thermodynamically stable. According to the band structure and partial density of the states, gallium is p-type doping. Impurity bands below the conduction band lead the absorption spectrum moves in the infrared direction. Arsenic doping has impurity level passing through the Fermi level and is n-type doping. The analysis of optical properties confirms the value of bandgap and doping properties.

Formation,Stability,Geometry and Band Structure of Organically Surface-Modified Germanane

Surface modification may be an effective means for controlling the properties of germanane, i.e., hydrogenated germanene. In this work, we investigate the formation, stability, structure and electronic properties of surface-modified germanane that results from the hydrogermylation, alkoxylation, aminization or phenylation of germanane. By assuming the typical organic surface coverage of -33%, we have com- pared organically surface-modified germanane with germanene and germanane in the framework of density functional theory. It is found that organically surface-modified germanane may all stably exist despite the endothermic nature of organic surface modification. Organic surface modification leads to the de- crease of the Ge--Ge bond length and the Ge--Ge-Ge bond angle ofgermanane, while causing the buckling distance of germanane to increase. Hydrogenation makes germanene change from a semimetal to a direct- bandgap semiconductor. Organic surface modification further impacts the band structure of the resulting germanane. Hydrogermylated/alkoxylated germanane is a direct-bandgap semiconductor, while aminated/ phenylated germanane is an indirect-bandgap semiconductor. All the organic surface modification gives rise to the increase of the bandgap of germanane.