| Since the advent of graphene,two-dimensional materials have attracted the attention of many researchers because of their superior properties which are different from bulk materials.The direct band gap and valley degree of freedom characteristics of monolayer Mo S2 inspire the application of transition metal chalcogenide in optoelectronic devices.1T-Ta S2,due to the complexity of its charge density wave(CDWs)phase,also set off a wave of research interest.More interestingly,when two monolayer materials are overlapped to form heterojunction,the photoelectric performance is better than that of single monolayer materials,such as Mo S2/WS2heterostructure.In contrast to the large family of transition metal sulfides,the research on transition metal oxides is rare.We stripped a single layer of oxidized platinum from bulk oxidized platinum,constructed Pt O2/Mo S2 heterostructure,and calculated and analyzed their electrical and optical properties.Ta S2/MX2(M=S,Se;X=S,Se)heterojunction,to control the electronic properties of sulfonate.The main research contents of this thesis are as follows:(1)Based on the first principle,it is calculated that single-layer platinum oxide is an indirect band-gap semiconductor with good dynamic stability.By comparing the energy of Pt O2/Mo S2 heterostructure in different ways,the Pt O2/Mo S2 heterostructure with the smallest energy was selected.On this basis,the energy band,density of states and optical properties of the most stable structure heterojunction are calculated.It was found that the electrons and holes of the Pt O2/Mo S2 heterostructure were located in the layers of oxidized platinum and molybdenum sulfide respectively,indicating that the model was a type II van der Waals heterojunction structure.Pt O2/Mo S2heterostructure has a higher absorption coefficient than monolayer Mo S2,which is beneficial to the absorption of light,and will have a broad application prospect in the field of future photoelectric devices.(2)The band and state density of 1T-Ta S2 in the undistorted phase at high temperature and the charge density wave phase at low temperature are studied by using the first principle.Under the condition that only spin polarization is considered and no spin orbit coupling is added,band spin polarization will not occur in high temperature structures.However,as a structure at low temperature,the energy band will be polarized by spin,resulting in band splitting.From this,we studied the influence of the substrate on the energy band of tantalum sulfide under high and low temperature by using the transition metal chalcogenide as the substrate.After considering the self-selective polarization,the high temperature structural band remains intact after the substrate is added.Interestingly,the band splitting of the low temperature tantalum sulfide structure under the substrate was inhibited.Our calculations show that the addition of transition metal chalcogenide can inhibit the spontaneous splitting of the transition metal chalcogenide.This conclusion is of great significance to study the electronic properties of tantalum sulfide in charge density wave phase. |
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