Date of Graduation

2015

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

David Lederman

Committee Co-Chair

Pavel Borisov

Committee Member

Xian-An Cao

Committee Member

Yuri D Glinka

Committee Member

Tudor Stanescu

Abstract

This dissertation summarizes the growth, structural and electrical transport properties of topological insulators based on Bi2Se3 compound grown by molecular beam epitaxy. In the first three chapters, I review the theoretical background and experimental procedures necessary to understand the properties of topological insulators. The next three chapters cover the results of the structural characterization and electrical transport measurements. The final chapter summarizes the overall results and suggests future directions for research on Bi2Se3 compounds. Topological insulators (TIs) are a new class of quantum matter with a bulk band gap and gapless metallic surface states. The spin and momentum degrees of freedom are locked and are robust against non-magnetic perturbations. Here, I study the growth, structural and electronic properties of Bi2Se3 and Mn doped Bi 2Se3 thin films. Bi2Se3/Bi2-x MnxSe3 thin films were grown on single crystal Al2O3 (0001) substrate by molecular beam epitaxy (MBE). Epitaxy was confirmed by reflection high energy electron diffraction (RHEED). Crystal orientation and lattice parameters were extracted from x-ray diffraction (XRD) measurements. The thin film thickness and roughness values were determined by fitting the x-ray reflectivity data (XRR) to a model based on optical scattering theory. To determine the Mn impurity site in Bi2-xMnxSe 3, extended x-ray absorption fine structure (EXAFS) measurements were performed at the Mn k-edge Finally, resistivity and Hall effect measurements were performed as functions of magnetic field and temperature. I focus on the weak antilocalization (WAL) and 2D magnetoconductance in the electrical transport measurements.

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