Comparative III-As-Bi Surface Morphologies and Microstructure and Disciplinary Literacy in MSE

Abstract

The first section of the dissertation concerns the growth and characterization of III-V-Bi films. The class of III-V semiconductors contains materials that are well-suited for applications in computation, detection, and energy conversion. Most common among these are the III-As materials, such as GaAs and InAs. When alloyed with Bi in small amounts, the bandgap of these materials decreases, allowing their use in applications in the infrared range, particularly sensing and lasing. The challenge lies in the controlled growth of III-As-Bi materials, as Bi tends to segregate in films and is immiscible with Ga, leading to inhomogeneous growths and rough surface morphologies. Addressing this challenge, we carried out a series of molecular beam epitaxy growths of GaAsBi and InAsBi films at different growth conditions, paying special attention to the resulting surface morphologies, microstructures, and Bi-compositions, as well as the kinetics and thermodynamics of the systems. We found that GaAsBi and InAsBi both exhibit four surface morphologies, those being different combinations or absences of droplets. In GaAsBi, the presence of Bi droplets particularly is associated with highly inhomogeneous films. The effect is still present in InAsBi films but is less prevalent. Our GaAsBi films reached Bi-compositions of 18.3% with droplets and 13.6% without droplets. The InAsBi films had Bi-compositions of up to 3.9% with droplets and 1.6% without droplets. The GaAsBi films generally match previous growth modeling, allowing us to estimate its kinetic parameters for growth. The InAsBi films match the modeling in some ways, allowing us to estimate parameters, but show features indicating that there are other kinetic processes to account for. The second section of the dissertation studies materials science and engineering (MSE) education. The process of disciplinary education involves introducing students to and enculturating students in the disciplinary culture, making students literate in the practices and values of the discipline. The theoretical framework of Disciplinary Literacy prompts researchers and instructors to ask, "What are the discipline-specific practices and values that are necessary to become a disciplinary practitioner, and how do we support students in becoming literate in those practices and values?" Though there are concepts and tactics that have been suggested for use in disciplinary-literacy-guided education, there remain the questions of how the concepts and tactics have been applied to education, and how they could be applied. To study the prevalence of disciplinary literacy concepts and tactics in contemporary MSE education, we conducted a literature review on published crystal structures and crystallography learning activities. Our findings suggest that certain concepts and tactics, such as the disciplinary cycle and the use of multiple types of representations, are implicitly understood and addressed in activities, while the tactic of learner role is not implicitly understood and certain aspects of it are neglected. To study the application of the disciplinary literacy concept of representational fluency in MSE education, we conducted studies comparing how students use paper-based and virtual-reality-based (VR) representations to complete activities about crystal structures, as well as how effective those different representations are. We found that students tend to use the two types of representations in different ways, and that while the VR-based representations helped students to complete difficult parts of the activity more correctly, they were less likely to remember what they learned. Implications of our findings for both sections are further discussed.