The electronic structures of graphene-MoS 2 heterojunction under tension and external electric field were examined on the basis of density-functional theory. The tension of MoS 2 changes the hybrid structure from semiconductor to metal. The transition is from the sensitive dependence of the bandgap of MoS 2 on the lattice constant. The vertical electric field has little influence on the bandgap of MoS 2 , while it can also adjust the charge transfer between monolayer MoS 2 and graphene. In addition, the Schottky barrier is linearly dependent on the electric field intensity with an effective vacuum spacing of 1.3 Å. It is also discussed in detail that the bandgap of MoS 2 dependence on the lattice constant and the S−S spacing. S ince the successful invention of isolated graphene in experiments, 1 a new materials fieldtwo-dimensional (2D) materialhas received much attention. It is a popular material for manufacturing the miniaturization and integration of electronic devices, such as layered electrodes 2,3 and thin film electronic devices. 4 Although the most famous 2D material, graphene, has many excellent properties and has been integrated into many different applications, its gapless-semiconductor band structure may be an obvious disadvantage in some cases. 5 Band gap is necessary in many application fields, such as light-emitting diode (LED), 6 solar battery 7 and transistor technology. 8 This disadvantage restricts the application of graphene in many areas. The molybdenum disulfide 9 is another kind of 2D material. The atomic structure of monolayer MoS 2 is two S-layers sandwiching a Mo-layer, and the atoms in layers are hexagonally packed. 10 It has good chemical and thermal stability, large specific surface area, and high surface activity. 11−14 With unique physical and chemical properties, it has potential application in catalysis, lubrication, and electrochemical lithium storage. 15−17 Single-layer MoS 2 is a direct bandgap semiconductor, which has very strong luminous intensity. 18,19 Moreover, it can be used as a channel material to manufacture an ultralow standby power field effect transistor with high current switch ratio and high electron mobility. 17 The layers of different 2D semiconductors can be stacked to form semiconductor heterojunction, and the novel physical phenomena in such heterojunctions have also become a focus of international nanoscience. Currently, the hot research of nanodevices is based on the heterojunction formed by graphene and MoS 2 , which is a new type of 2D layered heterojunction; the device has a light weight, low power consumption, and flexibility. 20−26 Experimentally, 27 the growth of MoS 2 on graphene will increase the electron transfer rate and improve the electrochemical performance. It has shown very good performance for lithium ion batteries and aerogels. 28−31 It can also result in a tunable photoresponsivity. 32 Theoretically, the electron mobility of the heterojunction is comparable to graphene. 33 Moreover, the bandgap can be changed by adjusting the interfacial...
