Design And Property Modulation Of Novel Phosphorene Based Two-Dimensional Heterostructures

Following the roadmap of the Moore's Law,the process technology of integrated circuits keeps to be scaling down and approaches the 10 nanometer nowadays.It has become a consensus that the technology will move into sub 10 nanometer in the near future.However,the ordinary three dimensional materials would result in evidently short channel effect with mobility being reduced rapidly,which can severely deteriorate the device performance.Family of two dimensional materials starting with graphene possesses ultra-thin thickness,high mobility and low dielectric constant,and can suppress issues from the short channel effect and reduction of mobility,which therefore attracts much attention from the microelectronic industry.In addition,novel physical properties induced by the quantum confinement effect along out-plane direction have also attracted much interest.Recently,two-dimensional phosphorene materials represented by black phosphorus and related devices show excellent performance and wide applications,and therefore turn to the hot research field in two-dimensional materials.Nevertheless,ranging from design and optimization of device structure to fabrication process of material and device,there are still many issues existed.For example,understanding of defect and unintentional doping effect in the fabrication is still not clear.Further design of phosphorene/two dimensional material devices of high quantum efficiency is also one of the essential parts,which are need for research and further industrial application.In this dissertation,above related issues are systematically studied with density functional theory of first principle.On one hand,typical experimental issues are analyzed from microcosmic views.On the other hand,we put forward several tunable multi-function device of potentially high quantum efficiency.The specific research contents and achievements of this dissertation are as follows:?.Unintentional doping effect in black phosphorus with hBN substrate was investigated,and we developed a new method for intentional doping via indirect effect from defects in substrate.We found that vacancies in the hBN substrate can indirectly introduce n and p type doping into black phosphorus via van der Waals(vdW)effect.Unintentional n type doping only presents in the case of isolated nitrogen vacancy,and unintentional p type doping effects present in most cases including di-vacancies,which well explains the experimental results of previous studies.Besides,black phosphorus can also influence the spin-polarized property.The study not only revealed a new doping route in black phosphorus based devices,but also developed a novel and non-contact method for realizing doping effect in semicondcutors,which pave the theoretical way for high efficient doping of 'zero impurity‘in the age of More Moore.?.With anisotropy,we proposed a new method to realize high quantum efficiency in the vdW heterostructures,and meanwhile put forward a novel tunable black phosphorus-HfS2 vdW heterostructure of high quantum efficiency.We found that the heterostructure naturally forms a type II band offset with unexpected highly anisotropic band dispersions.The effective mass then reveals the origin of high quantum efficiency and its implementation.We therefore proposed a new method to realize high quantum efficiency in the vdW heterostructures.The mechanism of linear gate manipulation is revealed with effective differential charge density.Based on these properties,we put forward a novel tunable electronic\photoelectric devices of high quantum efficiency with phosphorus-HfS2 vdW heterostructure.Compared with previous black phosphorus-transition metal sulfides heterojunctions,black phosphorus-HfS2 heterojunction not only fulfills the need of essential spatial charge separation,but also possesses superior current performance of high mobility and carrier density.?.The regulating electronic property of blue-graphene heterojunction via normal strain was studied,and we proposed a normal strain tunable blue phosphorus-graphene based vdW heterojunction,which offers new route for manipulation of electronic properties in two-dimensional heterostructures.As for the strain free case,the heterojunction forms an n type schottky with barrier of 0.4 eV.Appling normal tensile strain can lower the barrier height,and normal compress strain can shift down the Dirac cone rapidly with transformation of schottky from n type to p type.?.We put forward novel blue phosphorus-arsenene lateral heterojunction and a gate tunable electronic device.The thermodynamic stability,electronic structure and other properties were studied.We found that heterojunctions of all width fulfill the condition of synthesis,and are stable in the room temperature.Heterojunctions can spontaneously form a direct band semiconductor with type ? band offset,and therefore overcome the intrinsic indirect band nature in blue phosphorus and arsenene,which paves a new way for photoelectronic devices of high quantum efficiency.Based on the band structure,a novel gate tunable electronic device of 4 terminals was proposed.As compared to the field effect transistor in the conventional microelectronic industry,device proposed shows high on state current and on-off ratio,and therefore offers new route for realization of high-density integrated circuits with high performance in the microelectronics industry.