Synthesis Of Bi₂Te₃ Nanowires Using Gold-catalyzed Chemical Vapor Deposition

Bi2Te3, as a V-VI group element compound semiconductor, arouse enormous interest because of its unique thermoelectric effect, and trigger a new round of research upsurge more due to its three-dimensional topological insulators structure. There is electron spin-orbit coupling in the material’s surface state, which makes it could become an excellent material for the preparation of spintronic devices with low energy consumption at room temperature. As the larger surface-to-volume ratio, the surface state is dominant in the nanoscale topological insulators, resulting in the better surface and interface effect. At present, it is hard to synthesis high quality samples of the Bi2Te3 nanowires in the laboratory, which constrains the progress of research on the surface state of Bi2Te3. Therefore, in this thesis, we synthesized Bi2Te3 nanowires by gold-catalyzed chemical vapor deposition, and then we explored the influence of gold nanoparticles and macroscopic experimental conditions on the growth of Bi2Te3 nanowires.The main research results are as follows:1. At first, gold film(3 nm) were deposited on the <100> silicon wafer by thermal evaporation. The nanowires were synthesized on the silicon wafer by using the high purity bismuth telluride powder as evaporation source. Bismuth telluride nanowires with high purity, good crystallinity and stoichiometric ratio of 2:3 were synthesized at 420℃, 60 SCCM argon gas were introduced to the tube for 4.5h. After the reaction, the furnace was cooled to room temperature under vacuum.2. The effect factors, such as gold nanoparticles and macroscopic experimental conditions(carrier gas flow rate, reaction temperature and reaction time), for the growth of the Bi2Te3 nanowires were also studied. Main conclusions are as follows:(1) It shows that the nanostructure is Te crystal without gold as catalyst nanoparticles, while it became bismuth telluride with gold catalyst nanoparticles;(2) the carrier gas flow mainly decides the best deposition area of bismuth telluride nanowires;(3) the reaction temperature mainly affects the growth speed of nanowires which determines the nanowire growth orientation;(4) the reaction time mainly influences the nanowires longitudinal dimension.On the basis of the controllable preparation of Bi2Te3 nanowires, we plan to build the nano-device based on bismuth telluride nanowires, then study the electrical characteristics and surface state of bismuth telluride one-dimensional nanostructures at low temperature.