THE ELECTRONIC PROPERTIES OF THE QUASI-ONE-DIMENSIONAL TRANSITION METAL TRICHALCOGENIDES: TiS₃ AND ZrS₃

Authors

Simeon Gilbert, University of Nebraska-LincolnFollow

First Advisor

Peter A. Dowben

Date of this Version

9-2020

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfilment of Requirements For the Degree of Doctor of Philosophy, Major: Physics and Astronomy, Under the Supervision of Peter A. Dowben. Lincoln, Nebraska: September, 2020

Copyright © 2020 Simeon James Gilbert

Abstract

The transition metal trichalcogenides are a class of materials formed by 1D chains of covalently bound MX₃ (M=Ti, Zr, Hf, Ta, Nb; X=S, Se, Te) trigonal prisms which are held together by weak van der Waals forces to form 2D sheets. Because of their superior edge termination, these materials suppress edge scattering effects that plague other two-dimensional materials thus enabling devices scaling to widths below 10 nm. Furthermore, this quasi-one-dimensional structure results in highly anisotropic electronic and optical properties which were examined through angle resolved photoemission spectroscopy and scanning photocurrent microscopy. These measurements show that the hole carrier masses are drastically altered along different in-plane crystallographic directions and that the photocurrent production in these materials is strongly dependent on the polarization of the exciting light. Angle resolved photoemission spectroscopy and X-ray absorption spectroscopy indicate that TiS₃ and ZrS₃ exhibit strong metal-sulfur hybridization within both the conduction and valence bands. A combination of X-ray photoemission spectroscopy and device measurements were utilized to show that strong bonding with the surface sulfur atoms in TiS₃ prevents Schottky barrier formation with Au and Pt metal contacts. Furthermore, there are indications from both scanning photocurrent microscopy and X-ray magnetic circular dichroism measurements that these materials can support symmetry protected spin-polarized currents which could be utilized to create spintronic devices. When these findings are combined with the transition metal trichalcogenides’ superior edge termination, it becomes clear that these materials are promising for various applications in the fields of nanoelectronics, optoelectronics, and spintronics.

Advisor: Peter A. Dowben