Exploring the non-ambient behavior of ferroelectric HfO2-based materials in pursuit of brain-inspired computers

Exploring the non-ambient behavior of ferroelectric HfO2-based materials in pursuit of brain-inspired computers

Presenter: Joshua Adkins, UIC

Abstract: Any presumed merit of artificial intelligence (AI) is overshadowed by the deleterious environmental impact of the hardware & infrastructure used to support its development. AI data centers house vast arrays of graphics processing units (GPUs) that require hundreds of terawatt-hours (TWhs) of non-renewable energy and hundreds of millions of liters of potable water per year in the United States, alone. A solution to the energy inefficiency of AI hardware resides in neuromorphic computing, which emulates the human brain’s ability to both store and process information through synaptic connections between neurons for energy-efficient operation, neuromorphic computers eliminate the energy costliness of von Neumann architectures through the creation of efficient artificial neural networks. One of the most pressing challenges pertaining to the realization of widescale neuromorphic computing architecture is one of a materials science nature: what materials should be selected to serve as the neurons within a brain-inspired computer? To this end, nanoscale functional materials like ferroelectric hafnia (HfO2) might offer an answer.

HfO2-based materials (HBMs) are remarkable for their ability to exhibit ferroelectricity and memristance at nanoscales—two properties that can enable HBMs to serve as synapses in energy-efficient neuromorphic computers. However, HBMs are held back by two major challenges: the instability of the metastable phase that enables ferroelectricity, and the complexity of their oxygen-based defect dynamics. The instability of HBMs does not simply make reproducible synthesis challenging; it also jeopardizes long-term performance. Understanding this instability is complicated by the behavior of oxygen vacancies, defects reported to be critical to both the stabilization of the ferroelectric phase of HBMs and partially responsible for device fatigue with time. In consideration of these challenges, I will share some of the collaborative work I have conducted to study the electrical behavior of ultra-thin epitaxial HBMs under non-ambient conditions. In our work, my collaborators and I find that (1) HBM behavior varies greatly as temperatures decrease towards a cryogenic regime and defect dynamics become sluggish, and (2) strain in HBMs, while difficult to engineer in principle, can exert subtle effects on thin film stresses during growth that influence phase stability and resulting material performance. Our findings contribute to an ever-increasing body of knowledge pertaining to the characteristics of HBMs, which will be relied upon to design and deploy the neuromorphic computers of the future.

Speaker bio: Joshua Adkins is a Bridge to Faculty postdoctoral research associate in the Department of Civil, Materials, and Environmental Engineering at the University of Illinois Chicago (UIC). He received his B.S. in Chemistry (A.C.S.-certified) from Xavier University in Louisiana in 2018, and completed his Ph.D. in Materials Engineering at the University of Illinois Chicago in 2024. His research interests include the design and investigation of morphologically engineered fluorite- and wurtzite-based ferroelectric complex oxides, and their study under variable-temperature conditions. By modifying both the atomic and thermal landscape of these multifunctional materials, Joshua’s research aims to understand and control the properties of old and new ferroelectrics to enhance their properties and expand their applications in nanoelectronics. He has also supported efforts to recruit, retain and nurture racially underrepresented college students through work that develops students’ engineering identities, and through the development of pre-college curricula and programming for incoming engineering freshmen. More broadly, Joshua aims to prepare future generations of critically conscious scientists and engineers to contribute to the construction of a more just and humane society.

Faculty host: Pai-Yen Chen, pychen@uic.edu