Study On Fabrication And Properties Of New Photoelectric Thin Film Sulfide Semiconductor Materials

Sulfide semiconductor is a kind of important semiconductor,generally with excellent photoelectric properties,abundant raw materials,the industrialization advantage of low cost,and with extensive applicability and wide application prospect in the field of modern photoelectric,such as photoelectric detector,electroluminescent device,photoluminescence device,solar cell and field effect transistor.The rapid development of the era and technology requires the development of new semiconductor materials which surpass traditional materials with more excellent and special properties.The development direction of new sulfide semiconductor include broad bandgap semiconductor with high temperature resistance,big breakdown voltage and wide spectrum,multiple compound semiconductor with diversity,low dimensional semiconductor with novel and flexible properties,etc.The research on the preparation and characteristics of these new sulfide semiconductors can better promote related applications,emerging industries and even technological revolution.In this dissertation,the study on several new sulfide semiconductor thin film materials including broad bandgap semiconductor zinc sulfide ZnS,quaternary sulfide Cu₂ZnSnS₄?CZTS?,two-dimensional layer semiconductor molybdenum disulfide MoS₂ is as follows:1.ZnS thin films with good crystallinity are obtained with magnetron sputtering method which has good controllability and repeatability and is good to large-scale production.Besides the wide band gap property,the ZnS films have a uniform density,good light penetration,high refractive index,small extinction coefficient and good lattice-matching with absorber materials.It suggests that magnetron sputtering method is very suitable for the preparation of ZnS thin film.The best sputtering parameters are obtained through optimizing.The properties of ZnS thin films are studied through various advanced measurements including ellipsometry.2.To solve the p-type doping problem of n-type semiconductor ZnS,the atomic ratio is studied through heat treatments affecting lattice defects.It is proved that sulfur atmosphere annealing can effectively increase the ratio of S atoms by comparative study with vacuum annealing and sulfur atmosphere annealing.Obviously excessive S atomic ratio is realized with three factors including ZnS ceramic target,suitable preparation method of magnetron sputtering which is good to get the films with similar atomic ratio as target and is easy to form Zn vacancies,and S atmosphere annealing.The experimental results show that the properties of wide band gap,optical constants and microstructure of ZnS films non-stoichiometric are not affected obviously,so the optoelectronic applications will not be affected.On the basis of experiment,a practical p-type intrinsic doping idea is proposed that through the above three factors,and further increasing the target S,Zn composition differences,strengthening the intensity of annealing sulfur atmosphere.It can be expected that n type ZnS semicoductor is changed to the p type.Then that could broaden the photoelectric applications of ZnS semicoductor films.3.The electronic properties and optical properties of the two basic structures including kesterite?KS?and stannite?ST?of CZTS photovoltaic absorber materials are studied.The systematic calculations are completed with density functional theory.The electronic band structure and density of states,and optical properties including dielectric constant absorption coefficient and reflectivity,optical conductivity and energy loss function were calculated.It is found that the electronic structure and optical properties are in no obvious relevance with different arrangements of Cu and zinc atoms.The two CZTS are both suitable for film solar cells absorbers.The ground state structure of CZTS is found.The CZTS electron transition mechanism related to the absorption of solar cells was studied.The optical properties in the visible range of the two CZTS structures are compared.To deal with the problem of fabrication and impurities due to the complex elements of CZTS,the fabrication of CZTS film is studied by layered metal precursor evaporation and sulfurization method and single target magnetron sputtering method.Finally CZTS films without obvious impurities are obtained by the two methods after optimizing the parameters.4.The MoS₂ films with a few atomic layers are obtained with single target magnetron sputtering and annealing method which is rare in preparation of MoS₂ with such thickness.This broadens the preparation methods of few-layer MoS₂ films.The controlled growth of few-layer MoS₂ films is realized through optimizing the preparation parameters.Organic small molecule semiconductor Rubrene film is deposited onto the atomic level two-dimension MoS₂ film.The combination properties of organic and inorganic films are studied by various spectrum analysis.The experiment results show that the two films have good affinity,and the good adsorption ability and the unique two-dimension layered crystal structure could improve the stability and quality of rubrene.