Simulation Study On The Regulation Mechanism Of Electrical Properties Of Germanene Based On Structural Design

Germanene is one of the most important two-dimensional nanomaterials since the discovery of graphene and silicene.It has attracted more attention to its excellent physical and chemical properties.However,germanene with a small band gap greatly limits its application in nanoelectronic devices.Relevant studies have shown that the atomic structures and electronic properties germanene can be effectively tuned by means of organic molecular adsorption,substrate and external electric field.This paper adopted the density functional theory calculation method with van der Waals force to study the mechanism of the organic molecular adsorption and substrate on the atomic structures and electronic properties of germanene under external electric field.The main research contents and conclusions are as follows:(1)In the germanene model,organic molecules(OMs)with benzene and hexafluorobenzene were adsorbed at eight high symmetry positions to form OM/germanene systems with different configurations.By calculating the adsorption energy,the stability of OM/germanene systems was determined.This paper mainly investigated the atomic structures and electronic properties of OM/germanene systems with the most stable configurations under external electric field.The research results showed that the adsorption of organic molecules breaks the symmetry of the germanene sublattice through weak interaction,opening a sizable band gap at the Dirac point.The benzene/germanene and hexafluorobenzene/germanene systems open the band gaps of 0.036 and 0.005 e V at the K point,effectively increasing the band gap of germanene.In addition,by applying external electric field,the benzene/ germanene and hexafluorobenzene/germanene systems can widen the band gap of germanene to 0.680 and0.521 e V,respevtively.(2)On the basis of OM/germanene models,the fully hydrogenated germanene(germanane HGe H)was further used as the substrate.The research results showed that there are no covalent bonds between germanene and the HGe H substrate,and stable double-layer heterostructures through weak interaction.Since the HGe H substrate destroys the symmetry of the sublattice of germanene,it induces germanene to open the band gap in Dirac point.The band gaps of the benzene/germanene/germanane and hexafluorobenzene/germanene/ germanane systems are0.152 and 0.105 e V,respevtively.Under external electric field,the band gaps of the benzene/germanene/germane and hexafluorobenzene/germanene/germanane systems can be increased to 0.463 and 0.358 e V.Both the OM/germanene system and OM/germanene/germanane systems can achieve a wide range of approximately linearly tunable band gaps.The organic molecules,germane substrate and germane are only designed as the heterostructures by weak van der Waals forces,which does not form a chemical bond.Thus,the carrier mobility of germanene can be well maintained.This paper proposes an effective design method that can tune the band gaps of germanene,providing an important theoretical guidance for the application of germanene in field-effect transistor and other nanoelectronic devices.