Vapor Synthesis Of Two-dimensional ReS₂ And Electronic Modulation And Application Of Its Anisotropy

Due to the angle-dependent physical and chemical properties from asymmetric crystal structure,two-dimensional anisotropic materials exhibit excellent orientational-resovled optical,electrical and mechanical properties,making it possess great application prospect in the field of anisotropic electronics and optoelectronics.Rhenium disulfide（ReS₂）,which is one of the typical representatives,had attracted extensive attention because of its unique physical properties and remarkable anisotropy.The Peirs distortion in its crystal lattice leads to strong anisotropy and weak interlayer coupling,which shows great application potential in the fields of new logic devices,photodetectors and thermal response devices.Unique characteristics of linear dichroism makes it stand out in the field of new angle-sensitive electronics and optoelectronics.Although rhenium disulfide has many excellent properties and wide application,its controllable preparation has been the pain bottleneck,restricting the development and application of the material.It is worth noting that two-dimensional ReS₂nanoflakes and film can be controlled synthesized on mica with the size of hundred microns via chemical vapor deposition in recent years,but this growth substrate is incompatible with the traditional semiconductor technology which is another difficult problem that hinders its real application.In addition,for the emerging anisotropy application,whether the degree of anisotropy difference can meet the actual application requirements,how to expand the anisotropy difference and realize controllable anisotropy modulation will be the urgent problem to be solved in the future application field of angle-sensitive devices.Based on this,this paper focuses on the controllable synthesis,anisotropic modulation and application of ReS₂ and carries out this following works:（1）An alkali metal salt assisted CVD synthesis method for ReS₂ was proposed to solve the problem of asymmetric growth on silicon substrate with irregular dendritic structure or flower-like structure.The additional source KCl can effectively reduce the melting point of Re reactant and debase the growth barrier of the reaction atoms on the substrate surface,realizing the growth of 2D large size thin ReS₂ on the silicon substrate.The anisotropic properties of ReS₂ were studied.High anisotropic mobility ratio（～2.8）and anisotropic photoresponsivity ratio（～5.6）show excellent anisotropic electronic and photoelectronic properities.This novel growth strategy for ReS₂,which is compatible with traditional semiconductor technology,provides a reference for controllable synthesis of other two-dimensional materials.（2）Carrier doping of ReS₂ was carried out by introducing the gate and temperature field.And the evolution of its electron anisotropy was systematically studied,which proved that gate and temperature can change effectively electronic anisotropy.At low carrier doping levels,carrier scattering from defects or vacancies in different orientation of ReS₂ plays an important role in the modulation process.On the contrary,the increase of carrier doping can suppress the scattering effect and restore the electronic anisotropy to its natural value.Carrier doping induced by gate and temperature not only reveals the close relationship between the anisotropy and defect/vacancy of ReS₂,but also provids some guidance for the anisotropy research of other anisotropic materials.（3）A unified change of carrier doping was realized by temperature and gate in last work.And in this work,P（VDF-Tr FE）/ReS₂ compound was implemented for achieving selectively carrier doping of ReS₂by using AFM tips.Ferroelectronic thin film P（VDF-Tr FE）was used as polarization layer,playing a role of sustainable gate filed.The electronic anisotropy of ReS₂ can be modulated controllablely and reversiblely by this way.Compared with the intrinsic anisotropy of ReS₂,the biggest electronic anisotropy value achieved by this new strategy increases nearly an order of magnitude.（4）2D CsPbBr₃/2D ReS₂ vertical heterojunction was synthesized via two-step growth strategy.The generation of anisotropy of CsPbBr₃ grown epitaxially on anisotropic ReS₂were investigated,demonstrating that strong interlayer coupling and electron transfer exist in heterojunction interface.The angle-resolved PL spectrum of CsPbBr₃ on heterojunction showed that anisotropic ReS₂ plays a key role for anisotropy of CsPbBr₃.The change of anisotropy of CsPbBr₃may be attributed to the redistribution of electronic state of CsPbBr₃caused by interlayer coupling.This strategy to induce anisotropy for other 2D materials by constructing ReS₂ based heterojunction provides new insight in the future anisotropic application of ReS₂.