The Study Of Epitaxial Bi₂Se₃ Films And Bi₂Se₃-based Superlattice

Topological insulator is a new quantum state material with some novel quantum properties,it has attracted much attention in recent years,and become one of the most intensively studied subjects in condensed matter physics today.Especially the compound Bi₂Se₃,which has been identified as superb three-dimensional topological insulator,have an insulating gap in the bulk and gapless on the surface at the protected of the time-reversal-symmetry and spin-orbit coupling.In addition,it also has the ideal material platform for the study of Majorana fermion,topological superconductor and the topological magnetoelectric effect.At the same time,Bi₂Se₃-based topological insulator can be used to artificially synthesize low-dimensional quantum materials like superlattices and quantum wells with other materials,which will exhibit more novel quantum physical properties and excellent thermoelectric properties.In this paper,we will study the three-dimensional topological insulator Bi₂Se₃,focused on the preparation of Bi₂Se₃ thin films on the silicon and sapphire substrates,and also the growth of Bi₂Se₃-based superlattice on sapphire substrate.The main work as the follow:1.Growth the high-index Bi₂Se₃ single crystal films on the high-index Si（211）substrate and 8°cut off Si（111）substrate via molecular beam epitaxy（MBE）method.At the period of experiments,we studied the effect of H and Bi passivation on the growth of Bi₂Se₃ thin films,for the Si（211）surface,H-passivation treatment does not produce high quality Bi₂Se₃ films,but for the Bi-passivation treatment,the surface of Si（211）is replace by the ordered Bi chain structure,which modified the Si（211）surface and facilitates nucleation and growth of the Bi₂Se₃ films.2.The RHEED,STM and HRXRD have been used to study the surface morphology and crystal structure of Bi₂Se₃ films epitaxial growth on the Si（211）and tilt Si（111）substrates,conclude that the Bi₂Se₃（00n）parallel to the Si（111）stepped surface via the van der Waals epitaxial growth mode.Since the Si（111）step surface has a certain angle with the substrate surface,and the Bi₂Se₃ film is parallel to the Si（111）surface,that means from this method we can growth the high-index of Bi₂Se₃ film.Foe the heterostructure of Bi₂Se₃/Si（211）and Bi₂Se₃/Si（111）（8°cut off）,we studied the electrical property by variable temperature I-V test,and calculator the Schottky barrier height were 0.14eV and 0.11eV,respectively.3.We studied the growth of Bi₂Se₃ thin films with controllable thickness on the sapphire substrate,on this basis,studied the growth of Bi₂Se₃/In₂Se₃ superlattice on sapphire substrate,and characterize its structure.The RHEED has been used to analysis the relationship between residual strain and the thickness of the superlattice in the growth process.At the same time,when studying the superlattice strain,we find that the thickness of In₂Se₃ layer has a great influence on the strain release and quality of the superlattice.At one cycle of the superlattice,appropriately reduced the thickness of In₂Se₃ layer and increased the thickness of the Bi₂Se₃ layer,will helpful to improving the quality of the superlattice.