Study On Structure And Transport Properties Of Bismuth Thin Films

With decreasing dimension, materials exhibit properties which bulk materi-als do not have. These properties and their related phenomena have attracted more and more attention nowadays. From the60s, bismuth (Bi) has drawn great interest for its low carrier concentration, small effective carrier mass m*and large Fermi wavelength. It is an idea material for the study of quantum transport and finite size effect. With the development of experiment technique and sensitiv-ity, deeper understanding of its electron structure and transport properties were gained generally. With all these progress, there are lots of puzzles and debates around Bi’s novel behaviors, and their origin are still obscured. In my Ph. D thesis, I will focus on the growth and transport properties of single crystalline bismuth films. In addition, the design of an in-situ transport measurement sys-tem.The main contents are listed below:1. Epitaxially growth of bismuth single crystalline films on BaF2by MBE. With in-situ RHEED, we observed a phase transition. By Grazing an-gle XRD, we determined the structures of both phases (pseudocubic and hexagonal) and also the stages of the growing process. In addition, the conductance measurement showed consistent results with the RHEED and XRD experiments.2. By study the dependence of Bi films’transport properties on thickness and temperature. We proved the existence of semiconductor phase in thin bis-muth films. This gives a strong argument to the long studied and debated problem. And also, we determined the semimetal-to-semiconductor transi-tion point.3. Base on our understanding that bismuth films’s transport properties are the joint effect of metallic surface state and semiconductor interior, we make up models to study the unclarified novel behaviors in the conductance and Hall effect of bismuth films. We proved quantitatively that these behaviors are the results of competition between the two component in the Bi films. 4. By studying the Shubnikov-de Haas oscillation in the bismuth films under low temperature and strong magnetic field, we found no indication of the theoritical predicted period. So the features beyond the Quantum limit of bismuth can not be deciphered as the Shubnikov-de Haas oscillation of its surface state.5. The design of a UHV compatible in-situ transport measurement system. In addition, ex-UHV anisotropic magnetoresistance experiment was taken to test the system’s working performance.