The interfacial formation energy per unit area of heterojunction (e) and heterojunction (f) for type II matching is 0.365 eV/Å 2 and 0.368 eV/Å 2, respectively. Among the three models of type I, the formation energy of heterojunctions (b) and (c) is lower than that of heterojunction (a). The interfacial formation energy per unit area of heterojunction (a), heterojunction (b), and heterojunction (c) for type I matching are 0.330 eV/Å 2, 0.327 eV/Å 2, and 0.328 eV/Å 2, respectively. The convergence criterion of the interaction force between atoms was no bigger than 0.03 eV/Å, and the maximum stress between atoms was up to 0.05 GPa. In the optimization, the convergence accuracy of energy was 1 × 10 −5 eV/atom. In the process of geometric optimization, the convergence test was carried out by keeping the two parameters, K point and cut-off energy, as single variables. 34 The K vector path was set by manually inputting coordinates. Considering the interactions in the van der Waals heterojunction, the graphene/MoS 2 heterojunction was accounted for by including the Grimme’s semiempirical dispersion correction (D2). The DFT-D2 method was employed to study the graphene/MoS 2 heterojunction. Due to the fact that van der Waals heterostructures need to be described in VDW functional, it was used during the calculation. CALCULATION METHODīy the first-principles, the graphene/MoS 2 heterojunction was theoretically calculated based on density functional theory (DFT). In this way, graphene can be applied in the semiconductor field. The graphene/MoS 2 heterojunction, which can open the Dirac point of graphene, is the combination between monolayer graphene and MoS 2 in the form of van der Waals heterostructure. 31 This trait makes up the shortcoming of graphene in application to the semiconductor. 29 Monolayer MoS 2 possesses 1.80 eV direct bandgap 30 and 1 × 10 8 on/off ratio. 19,24–28 MoS 2 is an important material of transition metal dichalcogenides. 20–23 Transition metal dichalcogenides (TMDs) with graphene-like inversion symmetry layered structure is another hot topic following graphene. 18,19 Bandgap opening of graphene has always been a research hotspot in the semiconductor field. 16,17 It is difficult to be applied in more sophisticated logic circuits. 6,7 Zero bandgap 8–11 and the Dirac point 12–15 of monolayer graphene lead to a poor on/off ratio. 2,5 Its excellent electrical properties have shown wide potential for applications in the field of conductors and semiconductors. 3,4 The carrier mobility of its single-layer structure is ten times more than that of silicon material. 2 Graphene has the properties of small thickness and high strength. 1 The two-dimensional material has been developed based on the appearance of graphene. They are combined or stacked in the z-axis direction through bonding or interatomic force. In the z-axis direction, its thickness is similar to that of a few atoms. The two-dimensional material is a kind of planar material that extends only in two dimensions, the x-axis direction and the y-axis direction in space. It indicated that the absorption of infrared light by the heterojunction was stronger than that by the MoS 2. The dielectric function of the heterojunction was not zero in the infrared range. Compared with MoS 2, its absorption intensity in the visible range improved. The maximum bandgap opening of heterojunctions was 14 meV. The band structures of nine heterojunctions were very similar. The graphene/MoS 2 heterojunction in a lattice matching way has the lowest relative energy. In addition, lattice matching mechanisms, stacking modes, electronic structures, and optical properties of the designed heterojunction structures were calculated. The accuracy of their models was verified. Based on the first-principles, the most stable monolayer graphene and MoS 2 were obtained through the convergence test. The graphene/MoS 2 heterojunction, which opens the Dirac point of graphene, can solve this problem. Graphene’s Dirac point in the band structure and no current switching ratio make it hard to be used in sophisticated logic circuits.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |