Controlled Preparation And Characterization Of Tungsten Distelluride Nanostructures

After the successful discovery of single-layer graphene by researchers since 2004,people in the field of basic research have paid much attention to graphene due to its unique crystal structure as well as excellent electrical,optical and thermal properties.Because of the large number of excellent properties of graphene,it has promoted the rise of the research of other low-dimensional materials in the academic circle.The successful synthesis of new two-dimensional materials,such as black phosphorus,molybdenum disulfide,molybdenum selenide and tungsten telluride,has enriched the family of two-dimensional materials to a large extent,which has also promoted the wide application of two-dimensional materials in the fields of electronics,information,energy and so on.In addition to having the properties of most two-dimensional materials,WTe₂ as a member of the two-dimensional material family also has many novel physical properties.The bulk material WTe₂ that was found by people for the first time has the features of unsaturated giant magnetoresistance.The magnetoresistance is still not saturated when the magnetic field reaches 60 T.Based on this research result,it makes WTe₂ receive extensive attention.According to the theoretical and experimental results,it indicates that WTe₂ is not only a two-dimensional topological insulator,but also a superconductor.The switching between two different electronic states can be realized through the external field.As for the above-mentioned WTe₂,it has a variety of unique physical properties,which makes WTe₂ become a research hotspot over the years.In this thesis,we have achieved the controllable preparation of tungsten telluride nanostructures based on the strategy of space confinement and precursor design.The following is the main research results of the thesis:1.By employing the atmospheric pressure chemical vapor deposition(CVD)method,the tungsten telluride nanostructures with different sizes and morphologies have been fabricated by the control of the oxidation time of tungsten foil at high temperature,the flow rate of gas and the confined space between substrate and tungsten foil.Moreover,we also realize the growth of tungsten telluride nanostructures on different substrates(Si O₂/Si,sapphire,glass,mica,and so on).2.The role of water in the growth process is discussed.Through the introduction of water in the growth process,it is able to promote the growth of tungsten telluride nanostructures.According to the analysis,it is found out that water can react with the precursor,which can better promote the growth of tungsten telluride.However,the introduction of excess water will inhibit the growth process and lead to the phenomenon of precursor poisoning according to the research.3.The changes of atomic thickness and surface potential of tungsten telluride nanostructures in atmospheric environment is systematically studied by using Atomic force microscopy and Kelvin force microscopy,which proved the instability of tungsten telluride in air.In addition,it also carries out the systematical research on PMMA protection strategy to prevent the oxidation of tungsten telluride nanostructures.