Growth And Characterization Of New Heterojunction Nanostructures In The Zn-Sn-O System

ZnO,SnO₂,Zn₂SnO₄ in Zn-Sn-O system are all outstanding oxide semiconductors which have high visible light transparency and high carrier mobility.They are the best candidate materials for the next-generation flexible wearable devices.However,single-component materials have limitations of their own,currently,there are three effective ways to improve the performance of semiconductors:nano-crystallization,doping,and heterostructure construction.The research of Sn-doped ZnO nanowires has been carried out for many years,but until recently,a novel SnO₂?ZnO?_m superlattice structure nanowires have been discovered,and it is expected to have better thermoelectric and catalytic properties.However,the related formation mechanism is still in doubt.In addition,the research works of constructing heterojunction materials by using ZnO,SnO₂ and Zn₂SnO₄ are popular,but some questions such as whether there is an epitaxial relationship between Zn₂SnO₄ and SnO₂ remain unresolved.In this thesis,the growth mechanism of oxide nanowires,the structural evolution of SnO₂?ZnO?_m superlattice and the structural relationship of SnO₂-Zn₂SnO₄ heterostructure are studied.Firstly,a number of parameters in the chemical vapor deposition process were adjusted to control the growth of ZnO and SnO₂?ZnO?_m superlattice nanowires,and SnO₂?ZnO?_m-Zn₂SnO₄ heterojunction nanowires were synthesized successfully.Through structural characterization and crystallographic simulation,it is determined that ZnO,SnO₂?ZnO?_m and Zn₂SnO₄ have structural inheritance,and the bond between them is Sn-O octahedral layer.At the same time,it is determined that SnO₂?ZnO?_m and Zn₂SnO₄ have the following epitaxial relationship:SnO₂?ZnO?_m[11???0]//Zn₂SnO₄[???01],SnO₂?ZnO?_m?0002?//Zn₂SnO₄?111?.Secondly,the SnO₂-Zn₂SnO₄ core-shell nanowires and heterostructure nanobelts were prepared by two-step chemical vapor deposition successfully.With side and cross-sectional structural characterization,it is determined that SnO₂ and Zn₂SnO₄ have the following three types of epitaxial relationship:SnO₂[101]//Zn₂SnO₄[101],SnO₂?10????//Zn₂SnO₄?13????;SnO₂[101]//Zn₂SnO₄[101],SnO₂?020?//Zn₂SnO₄?1???????;SnO₂[010]//Zn₂SnO₄[112],SnO₂????00?//Zn₂SnO₄?11????;...