Preparation And Electronic Transportation Performance Of Sb_2-xBi_xTe₃ Films

Topological insulation has special physical properties such as insulators in the bulk,conductive surface and boundary,and has a very wide application potential in the field of electronic devices.As the second generation of three-dimensional topology insulator materials,Sb₂Te₃,in addition to the topological properties,also has the characteristics of excellent thermoelectric properties,fast crystallization speed,good thermal stability.Therefore,preparing high-quality Sb₂Te₃ film has an important research significance for the application in the fields of thermoelectric,phase change storage.Sb₂Te₃ film will show more novel physical phenomena outside the original nature by doping other elements.In this work,we study the effects of molecular beam epitaxial process and content of Bi doping on the structure,morphology and electronic transport performance of the Sb₂Te₃ thin film.The main results are generalized as follow:（1）At different source furnace temperatures,beam ratios,and deposition temperatures,a series of Sb₂Te₃ thin films are grown on the Sr Ti O₃（111）substrate,When the source furnace temperature is Sb380 ^oC/Te300 ^oC,the beam ratio is Sb:Te=1:5 and the deposition temperature is 150 ^oC,the film achieves good epitaxial growth.The electrical transport performance of the films growing under the different deposition temperature indicates that the films are p-type conductive,and the carrier is hole.The deposition temperature affects the quality of the films crystallization,thereby affecting the carrier concentration and mobility of the films.Due to the existence of quantum coherent effects,the magnetoresistance of the Sb₂Te₃ thin film has a weak localization effect at low temperature.The resistance of the film with the temperature changing,shows metal-insulator transition and low temperature resistance upturn phenomenon,which may be caused by the correction of the conductivity of weak localization effect.（2）Under suitable deposition conditions,the Sb₂Te₃ thin films having different thicknesses（3.3-20 nm）were grown,and the increasing of the thickness can effectively increase the crystallinity of the film.The Sb₂Te₃ thin film with 3.3 nm thickness arises metal-insulator transition around 240 K,and the films with 3.3 and 6.7 nm thickness appear resistance upturn at low temperatures and weak anti-localization at low temperature and zero magnetic field because of spin-orbit coupling effect.（3）The Sb_2-xBi_xTe₃（0≤x≤1.4）thin films with different content of Bi doping were grown,and the appropriate amount of Bi doping can increase the crystallization quality of the film and decrease its surface roughness.Doping Bi elements can change the type of carriers and carrier concentrations of the films and make the properties of the electronic transportation of the film from the surface,body,and impurities which cause the Hall curve nonlinear.In addition,doping Bi elements will make the low temperature resistance upturn phenomenon more obvious and cause the conductivity of films distributing unevenly which results the linear magnetoresistance of the films.