Date of Graduation

7-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Degree Level

Graduate

Department

Physics

Advisor/Mentor

Salvador Barraza-Lopez

Committee Member

Hugh Churchill

Second Committee Member

Julio Gea-Banacloche

Third Committee Member

Huaxiang Fu

Keywords

computational, ferroelectric, monochalcogenides, tight-binding, two-dimensional materials

Abstract

This work discusses a new class of materials with novel properties that have only recently begun being studied. These materials are two-dimensional group IV-VI monochalcogenides, so named because they are formed from group IV (carbon group) and group VI (chalcogens) elements. These materials display several interesting physical properties such as ferroelasticity and ferroelectricity, and the contents within Chapters Two, Three, and Four concern a collaborative effort between theory and experiment between our group at the University of Arkansas and Dr. Kai Chang at the Max Planck Institute of Microstructure Physics in Halle, Germany in studying these properties. This thesis is arranged in five chapters, organized as follows: Chapter One introduces the basic ideas of two-dimensional monochalcogenides and their crystal structure and symmetry properties; Chapter Two discusses the observed standing wave patterns in electronic surfaces states in the ferroelectric domains of monolayer SnTe despite the absence of a potential barrier; Chapter Three discusses the evolution of the physical and electronic structure of SnTe from few atomic layers to near-bulk structures; Chapter Four discusses the ferroelectricity of SnSe, and how interactions with the graphene substrate lead to several differences in domain structure compared to SnTe; Chapter Five concerns tight-binding models, beginning with an overview of the general tight-binding method and the semiempirical Slater-Koster method, and details the construction of the models for SnSe, SnS, GeSe, and GeS using data from the SIESTA code, and presents the results. (All codes employed are in capitalized italic fonts, and all structural data are writte in A).

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