Modulation Of The Electronic Properties Of Black Phosphorus/molybdenum Disulfide Heterojunction By Uniaxial Strain

Ultrathin two-dimensional nanomaterials are a kind of nanomaterials with a single layer or a few atomic layers.The atoms in each layer are bonded by covalent bonds and the surface has no dangling bonds,and the interlayers are weakly bonded by van der Waals interactions.Due to the unique quantum confinement effect and interlayer coupling,two-dimensional materials exhibit exotic properties different from the bulk materials,such as high mechanical strength,suitable band gap and so on.Furthermore,the vertical stacked van der Waals heterojunctions composed of different two-dimensional materials have become one of the frontier scientific issues in recent years.The heterojunctions assembled by the two-dimensional system not only maintain the originally excellent properties of individual materials,but also bring novel physical properties due to the interface coupling interactions.Currently,various heterojunctions,such as graphene?Gr?/transition metal chalcogenides?TMDs?,TMDs/TMDs have been constructed,and these heterojunctions possess fast photodetection responsiveness,high carrier mobility and tunable band alignment,suggesting the potential applications in the field of new electronic/optoelectronic devices.Importantly,the effective tunability of electronic and optical properties is crucial for their applications,a lot of considerations such as strain,doping,applied electric fields and functional modification have been employed to modulate the electronic and related properties.Especially,strain engineering is recognized as a reliable and efficient method to tune the material properties,and the strain can be easily applied by growing materials on the flexible substrates without destroy the membranes.Although several achievements have been obtained to investigate the strain engineering of monolayer materials,a systematic study on the electronic and mechanical properties of heterojunctions?such as black phosphorus/molybdenum disulfide,BP/MoS₂?under uniaxial strain is still lacking,and its theoretical relationship at the atomic level needs to be further clarified.Therefore,in our work,we investigated the band engineering of BP/MoS₂ heterojunction under uniaxial strain.Based on the first-principles calculation method,the evolutions of BP/MoS₂heterojunction band structure with strain is analyzed,and the mechanical properties such as critical strain are predicted.In addition,we analyzed the relationship between band offset and bond parameters of BP/MoS₂heterojunction in terms of atomic-bond-relaxation approach,and clarified the physical mechanism of strain modulation from the atomic-level.The achievements are shown as follows:?1?Under uniaxial tensile strain,the band gap of BP/MoS₂monotonically decreases with strain,and the Mo-S bonds break down at10%strain.?2?Under uniaxial compressive strain,the band gap shows a slightly increases and then monotonically decreases,and the BP/MoS₂heterojunction has a semiconductor-to-metal transition at-11%uniaxial compressive strain in the y direction?armchair direction?and at-12%uniaxial compressive strain in the x direction?zigzag direction?.?3?The BP/MoS₂ heterojunction maintains the type-? band alignment under the uniaxial strain in the y direction.In addition,the BP/MoS₂ heterojunction possesses a type-? to type-? transition at-5%compressive strain in the x direction.