Rui Huang’s MS Thesis Defense

“Sputter Deposition and Characterization of Highly Textured BixTe1-x Thin Films”

Committee Members:
Prof. Nian-Xiang Sun (Advisor)
Prof. Marvin Onabajo
Prof. Yongmin Liu

Abstract:
The discovery of topological insulators (TIs) provides a direction for scientists to understand the Quantum Spin Hall Effect (QSHE) and Spin-Orbit Coupling (SOP)  in condensed matter physics. After a decade, people found that after the introduction of magnetism into TI, the Time Reversal Symmetry (TSR) is broken, producing Magnetic Topological Insulators (MTI). Meanwhile, with the deposition of TI on the Magnetic Insulator (MI), the Spin-Orbit Torque was found in TI/MI structures. Introducing dopants into TI is another method to produce MTI. Mn-doped,  Cr-doped, and Ni-doped TI thin films have been explored recently. Thus, the 3D TI, Bi2Te3, and MTI, Ni: Bi2Te3, thin film-based materials have been applied to some energy-efficient spintronic devices. However, according to the Bi-Te phase diagram, Bi2Te3 is one of the Bi-Te family. The narrow range of the Bi2Te3 phase is a challenge for people to deposit the correct phase on the InP (111) wafer due to the potential effect of defects.  In this Master thesis, the textured BixTe1-x and Ni-doped BixTe1-x thin films are deposited on the InP (111) substrate through the RF Magnon Sputtering Tool with a Te capping layer under different deposition powers, temperatures, and post-annealing time. After the X-ray diffraction measurement on three samples with various conditions, the textured Bi8Te7, Bi8Te9, and Ni: Bi8Te7 thin films are concluded based on the comparison between the theoretical XRD results with the experimental ones.