GOALI: Toward Improving Quality and Yield of Large-Area, Single-Crystal Sapphire Wafers via Fundamental Understanding of Bubble Engulfment During Growth

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Single-crystal sapphire has numerous potential applications ranging from armor to electronics. The cost of this material is dependent on the cost of processing, which is complicated by the presence of bubbles during growth of the crystal. A fundamental understanding of the behavior of bubbles during the growth of single-crystal sapphire is needed to enable the manufacture of high-performance materials at a low cost. This Grant Opportunities for Academic Liaison with Industry (GOALI) award supports fundamental research to understand the mechanisms of bubble growth and diffusion in sapphire single crystals. Computational models of the process will be developed to describe the formation and motion of these bubbles during the growth process, and provide insight for strategies to eliminate these defects. The work?will be carried out in consultation with GOALI partner, Crystal Systems?Innovations, LLC, who will provide?valuable, practical insight and supporting?sapphire crystal growth experiments.??New knowledge from this work has relevance to the?manufacturing of?single-crystal sapphire material, and has benefits in potential applications including transparent armor for national defense applications, touch-screen?faceplates in smart?phones, and substrates for the fabrication of energy-saving white?light-emitting-diodes (LEDs).??This?project?will fund the training of a graduate student who will be?proficient in multi-disciplinary and?technologically relevant issues involving?advanced manufacturing, materials engineering and processing,?and crystal?growth. In this research program, investigators will?develop, validate, and apply computational models to elucidate the?mechanisms?of bubble inclusion during sapphire crystal growth. This research will build?upon prior steady-state and dynamic models at the continuum level that have?been developed to study the physical mechanisms?that determine the pushing or?engulfment of a solid particle at a moving, solid-liquid interface. These?studies?will be carried out in consultation with GOALI partner, Crystal Systems?Innovations, LLC, who will provide?valuable, practical insight and supporting?sapphire crystal growth experiments.??This work will probe the?fundamental mechanisms by which bubbles?are engulfed during solidification, which is a particularly?challenging problem?associated with sapphire crystal growth. In addition to addressing the?underlying?scientific phenomena of heat transfer, fluid mechanics, phase?change, and particle-solidification front?interactions, a computational?approach of unprecedented rigor and accuracy will be developed to probe?nonlinear and dynamical aspects of these extremely complex phenomena.?Finally, a?deeper understanding of bubble and particle?engulfment phenomena during solidification will impact other?areas as diverse?as geological materials, reinforced metal-ceramic composites, multi-crystalline?silicon, and?biological cryo-preservation processes. 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.