Doctor of Philosophy (PhD), Ohio University, 2022, Physics and Astronomy (Arts and Sciences)

Amorphous materials have myriad applications. There are persistent challenges in understanding their structure due to the absence of long range order. Ab initio methods are useful tools to model these materials and determine their microscopic properties. To utilize materials for technological applications, understanding of electronic transport is of central importance. More specifically, for a heterogeneous system, determining conduction-active sites in the network may provide an insight to engineer the material for a desired application. In this dissertation, we describe and develop a novel method to project electronic conductivity onto real-space grids and visualize conduction-active sites in selected materials. To implement the method, we utilize the Kohn-Sham eigenvalues and eigenfunctions obtained from hybrid functional calculations. We then apply the method to study conduction mechanisms in insulating, semi-conducting, metallic and mixed systems. In this dissertation, we also describe atomistic modeling of two promising resistive memory materials: amorphous aluminum oxide (a-Al2O3) and silicon suboxide (a-SiOx). For the former case, we study the impact of transition metal Cu in a highly ionic host a-Al2O3 and discuss its effect to electronic structure and transport in the material. We reveal that the Cu atoms segregate and form a cluster or chain-like structure in the oxide host. We find that such Cu-cluster/chain like network forms the major conduction-active sites in the material. For the latter case, we present a-SiOx models with x = 1.7, 1.5 and 1.3 and study their structure and electronic transport. In our study, we find that the decrease in x results in the complexity of the network with different tetrahedral structures of the form SiSiyO4−y where y = 0 to 4. This results in different types of oxygen (O)-vacancy sites in the material. We propose that a-SiOx also has a potential as a computer security device: physical unclonable functions (PUFs) (open full item for complete abstract)

Committee: David Drabold (Advisor); Sumit Sharma (Committee Member); Eric Stinaff (Committee Member); Martin Kordesch (Committee Member); Gang Chen (Committee Member) Subjects: Physics