First-Principles Studies Of Structural, Mechanical And Electronic Properties Of Metal/Semiconductor Phase Interface Of Monolayer MoS₂

Molybdenum disulfide belongs to a kind of transition metal sulfides, and is attracted because of excellent lubrication performance. Like graphene, molybdenum disulfide is easy to form a a two-dimensional structure material. Compared with graphene of lacking of band gap, molybdenum disulfide has a band gap about1.7e V. Therefore, molybdenum disulfide has great potential as photoelectronic material.In this study, a series of phase hybrid molybdenum disulfide systems with rectangle unit cell and different lengths in the direction perpendicular to the MoS₂ sheet have been Studied.Atomic structures, thermodynamic stabilities, mechanical,electronic and transport properties of the phase interface of MoS₂ were investigated by using the first-principles. Depending on the arrangement of its S atoms, monolayer MoS₂ appears in many distinct phases, two of them exhibit substantially different electronic structures: 2H?trigonal prismatic, D3h? MoS₂ is a semiconductor and 1T?octahedral geometry, Oh? phase is metallic.The study result of structure of the zigzag?ZZ? and armchair?AC?type interface demonstrate the relationship between of formationenergy and the cell length. The results showed that with the increase of the cell length, the formation energies of both AC and ZZ type of the hybrid system can also increase. The ZZ type metal/semiconductor?1T/2H? interface are more energy favorable than AC type interface.The mechanical properties of 1T/2H MoS₂ phase interface were explored using density functional theory. We systematically investigate the mechanical strength of the 1T/2H MoS₂ phase interface. The ideal strength of monolayer MoS₂?2H? is obtained as22.24?26.01? GPa along the ZZ?AC? directions, which is good agreement with that from the experimental AFM measurement.Apparently, compared with that of 2H phase, 1T MoS₂ has weaker mechanic properties. Compared with that of 1T phase counterpart,the 1T/2H hybrid system take similar ideal strengths and even higher Young's modules. At the same time, phase interface do not decrease the mechanic properties as the grain boundaries does. It is obvious that the mechanics properties of the hybrid system are determined by the weaker domains, which are quite different with grain boundaries effects in polycrystalline graphene.Electronic density of states analysis shows that the electronic properties gradually transmitted from the metallic 1T phase to the semiconducting 2H phase for the structural abrupt interface.Non-equilibrium green's function method and density functional theory was used to study the transmission characteristics of the MoS₂ from AC and Zigzag ZZ directions with different kinds of leads.The conductance of 2H phase MoS₂ depended on the transport directions and lead types?2H phase or 1T phase?. System with 1Tphase MoS₂ phase as lead can impressively improve the transport properties compared with the 2H phase lead. Moreover, for the system with metal lead, enhanced conductance can be observed.Further investigate indicated that the conductance is sensitively rely on the distance between metal lead and 2D material.