| Summary: | 碩士 === 國立成功大學 === 物理學系碩博士班 === 100 === In the research, the topological insulator Bi2Te3 thin film grown on sapphire(0001) by molecular beam epitaxy (MBE) in different growth conditions have been studied by RHEED, AFM, XRD and R-T measurement. The structure of Bi2Te3 thin films have the crystal orientation and flat surface morphology when the growth condition is 330℃ substrate temperature and flux ratio of Te/Bi is about 10 to 15. In electrical measurement, the R-T behavior of Bi2Te3 thin films is various in different temperature range. According to references, the results present that the electronic properties of Bi2Te3 thin films is metallic between room temperature to 100 K, which is attributed to carrier transport from the impurity band contributed the Te vacancies in Bi2Te3 thin films. In the temperature range from 100K to 50K, the carrier movement gradually is reduced due to low temperature, which result in increasing resistance. The electronic properties of Bi2Te3 thin films is semiconductor. Finally, the characteristics of Bi2Te3 thin films convert to the nature of insulator in the lower temperature range(〈50 K). According to above results, the amount of Te vacancies modulate the carrier concentration in the Bi2Te3 thin film, it also change other physical characteristics of Bi2Te3 thin film. Therefore, the control of Te defect is an important research in Bi2Te3 topological insulator.
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