Research On The Preparation Of Bi₂Te₃ Nanometer Thin Films By Electrochemical Atomic Layer Epitaxy

Thermoelectric material is new functional material that can be used to convert thermal energy into electrical energy directly with carriers. It has been used in many fields, such as temperature control, thermoelectric power, cooling electronic devices, medical equipment, high temperature superconductor, aerospace equipment, air-conditioning of submarine and so on. The study shows that nano-crystallization or low dimensionization is one of the most effective methods to improve thermoelectric.Electrochemical atomic layer epitaxy(ECALE) exhibites outstanding properties, such as low cost, easily controllable and scalable process, deposition at ambient temperature and environmental benign and so on. ECALE is proved to be an advanced method for deposition of semiconductor compound nanofilms.The preparation of Bi2Te3 thin film by ECALE and kinetics of Te on Au and Bi-Au were discussed in this paper. Firstly, we introduced the research background of this work and made a detailed review to the basic principles, characteristic and influence factors and application of ECALE method, and the perspective and application of ECALE in new material is estimated.The process of Bi2Te3 thin film growth on Au substrate by using electrochemical atomic layer epitaxy (ECALE) was reported in this thesis. Cyclic voltammetic method was used to investigate the electrochemical aspects of Bi and Te on the Au substrate. On the basis of analysis, we found the peak of 0.1~0.3V is the UPD peak of Te on Au, and the peak between 0~-0.3V is the UPD peak of Te on Bi covered Au. The ECALE program was optimized and a 200-cycle film was deposited. X-ray diffraction, EDX quantitative analysis and FESEM observation were performed to characterize the substrates and deposits, and the results shows that the deposits are single phase Bi2Te3 compound with a 2:3 stoichiometric ratio of Bi to Te; and the deposits are dense and homogeneous with a (015) preferred orientation.Electrochemical kinetic behavior of Te on Au and on Bi-Au has been studied using voltammetry and chronoamperometry techniques, effects of PH value, concentration and scan rate were reported. Scan rate dependent cyclic voltammetry experiments reveals that the UPD process of the Bi layer from an Au electrode fulfilled three criteria. That means 2-D growth mechanism is the dominant process in the UPD process of Te.