Events Calendar

Mork Family Department of Chemical Engineering and Materials Science Seminar - Distinguished Lecture Series

Speaker: Professor Paul Salvador, Department of Materials Science and Engineering, Carnegie Mellon University

Talk Title: Combinatorial Substrate Epitaxy and the Design of Materials

Abstract: Over the past few decades, advancement in epitaxial growth of complex oxides has been remarkable. Most of these advances have been made using a surprisingly small number of commercially available single crystal substrates (perovskite, fluorite, corundum, rock salt, etc.). If appropriate substrates were available across all structural families, we would accelerate the design and synthesis of new materials with attractive properties. I will discuss our work on an approach to solving this dilemma, called Combinatorial Substrate Epitaxy (or CSE). In CSE we use epi-polished polycrystalline ceramics as substrates and automated electron backscatter diffraction as a non-destructive local structural characterization method. We map the orientation of hundreds of substrate grains prior to growth, then map film orientations on those same grains after deposition and use in-house programs to determine the epitaxial orientation relationships (ORs) across all of orientation space (in a single experiment). Importantly, each grain in a polycrystal behaves as an individual single crystal substrate, usually exhibiting grain-over-grain epitaxial growth. A bit surprisingly, there are only a small number (one or two) of epitaxial ORs observed across orientation space, which are largely independent of the surface orientation. On substrates where competitive polymorph nucleation occurs, the winner of the competition can be rationalized using observed ORs and planar matching on low-index orientations. Because of this, we have been able to develop a computational method that guides epitaxial synthesis. Density functional theory computations are combined with continuum models of nucleation to guide the selection of thermodynamically accessible materials and polymorph directing substrates. I will use a variety of film / substrate structural pairs to make these points, including BO2, B2O3, ABO3, A2BO4, and A2B2O7. I will describe how CSE opens the door for the predictive design of materials with new properties and the synthesis pathways to make them.

Host: Dr. Jayakanth Ravichandran

Location: 200

Audiences: Everyone Is Invited

Contact: Karen Woo/Mork Family