NSF Award
2329090
Non-technical Description<br/><br/>The demand for energy needed to store and process data is growing at an unsustainable rate. New technologies are clearly needed. Phase change materials, which can dramatically change their electronic, optical, and physical properties during phase transitions, offer a promising solution. Their tunability makes them promising candidates for emerging applications such as energy efficient in-memory computing. This FuSe project will explore a new class of phase change materials that combine five or more elements in comparable amounts. The field of materials science has been captivated by the discovery of such “high entropy” materials. For example, high entropy ceramics have unique thermal and mechanical properties not possible with simpler compositions. In this project, investigators will combine computational materials discovery with combinatorial synthesis to realize high entropy phase change materials. The most promising candidates will be characterized comprehensively and integrated into electronic and photonic computational devices. The team will establish a robust pipeline to educate the next-generation workforce. They will offer rotational internships so that students can work at different universities and in cross-cutting fields and promote their success through mentoring. The team will also create a partnership between the University of Maryland and Howard University, an HBCU, to promote the direct exchange of research mentorship and training.<br/><br/>Technical Description<br/><br/>The central hypothesis driving this Future of Semiconductors project is that high-entropy phase change materials (PCMs) can form a thermodynamically stable single phase when elements randomly occupy one type of lattice site and are present in high concentrations rather than as dopants. This structure, stabilized by large configurational entropy, will enable development of PCMS with low/zero resistance drift and large bandgaps (>1.5 eV) or extinction coefficient contrast (∆k~2-3) for optical memristors in the visible and infrared. The proposed research comprises four thrust topics to be conducted in a closed-loop fashion. 1) First-principles computation material discovery to predict previously unexplored entropy-stabilized PCMs. 2) Combinatorial synthesis via sputtering of selenides and tellurides and thermal evaporation of sulfides in order to explore multiple compositions in a single run. 3) Electrical, optical, structural, and compositional material characterization to reveal the intrinsic (permittivity, structure, vibrational modes, composition, conductivity, capacitance, etc.) and extrinsic (void formations, capping, geometry, substrates) factors dictating device performance. 4) Integration of PCMs into photonic and electronic devices to demonstrate optical and electrical memristors and memcapacitors with optimal performance.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
