| Summary: | 碩士 === 國立成功大學 === 物理學系 === 104 === In this study, we mainly investigate the proximity effect in topological insulator and magnetic insulator bilayer system. In the experiment, Bi2Se3Sb/CoFe2O4 heterostructure was fabricated by using the molecule beam epitaxial technique and the pulsed laser deposition system, respectively. To observe the surface state of topological insulator, since we essentially need to reduce the bulk carrier concentration. In next step, a series of heterostructure magnetoresistance results are measured by PPMS. In contrast to single layer sample, Bi2Se3Sb/CFO heterostructure samples can suppress the WAL phenomenon. Then, the MR results are fitted by the modified HLN equation and successfully obtain the size of surface state gap. We can efficiently decrease the bulk carrier concentration of Bi2Se3 by doping Sb. The temperature dependent resistance of heterostructure samples at different external magnetic fields are also measured and analyzed. The results indicate the phenomenon of surface band gap opening with increasing external magnetic field.
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