Study On The Electronic Properties Of Semiconductor, Metal Alloy, Topological Insulator And Semimetal Surfaces And Interfaces

Studying the electronic properties of semiconductor, metal alloy, topological insulator and semimetal surfaces and interfaces is interesting and useful not only for device applications, such as organic devices and spintronics, but also for the fundamental interest in solid state physics. In this thesis angle-resolved photoemission spectroscopy (ARPES) measurements together with density functional theory (DFT) calculations were performed at a series of surfaces and interfaces:organic semiconductor/inorganic substrate interface, metal alloy, topological insulator and semimetal. The main focus is on the electronic structures of these interesting surfaces and interfaces.First, adsorption of the tetracene molecule on the clean Si(111)-(7×7) substrate was studied by ARPES measurements together with DFT calculations. The changes in binding energy and work function as a function of the coverage indicate that there is an interfacial dipole at the interface. The DFT calculation shows that the molecule most possibly adsorbs near the top of a center adatom with the longer molecular axis along the [110] azimuth. Second, the strong Rashba splitting system Bi/Ag(111) surface alloy were investigated by temperature-dependent ARPES measurements, and we introduced a two dimensional fitting model to analyze the data in the entire measured energy range. A series of the imaginary part of self-energy was obtained, from which the electron-phonon coupling strength,λ, was extracted. It reveals a strong couplingλ≈0.55, and it is hardly energy independent. Furthermore, the surface states on the class topological insulator Bi2Se3 were studied, particularly the thermal and structural stability of the topological state. It reveals obvious time-dependent band bending near the surface, which induces the creation of 2DEG. The latter co-exists with the topological state. Moreover, the electron-phonon coupling strength only from the intraband contribution of the topological state is much higher than for the noble metals. In addition, the topological state appears to be strongly perturbed by a small concentration of surface defects. Finally, the electronic structure of Sb(110) was studied by ARPES, and it was compared with topological prediction. We find that the experimental results are partly consistent with the topological prediction, but it is hard to speculate in the directions with projected bulk states at the Fermi level.