Materials by Design: Heterostructures with Targeted Nanoarchitecture and Tunable Properties

Wednesday October 28, 2015 4:00 PM

Materials by Design: Heterostructures with Targeted Nanoarchitecture and Tunable Properties

Speaker: David C. Johnson , University of Oregon
Location: Spalding Laboratory 106 (Hartley Memorial Seminar Room)

We have shown that by controlling the composition of an amorphous intermediate on the nanoscale it is possible to kinetically control the self-assembly of new nanostructured compounds consisting of two or more compounds with different crystal structures that are precisely interleaved on the nanoscale. We have used this approach to synthesize hundreds of new metastable compounds with designed nanostructure, including structural isomers. Many of these materials have unprecedented physical properties, including the lowest thermal conductivities ever reported for a fully dense solid, systematic structural changes dependent on nanostructure, and charge density wave transitions. The designed precursors enable diffusion to be followed and quantified over distances of less than a nanometer, providing insights to the mechanism that gives control of the nanoarchitecture of the final product. We believe the ability to prepare entire families of new nanostructured compounds and equilibrating them to control carrier concentrations permits a new "thin film metallurgy" or "nanochemistry" in which nanostructure and composition can both be used to tailor physical properties, interfacial structures can be determined for precisely defined constituent thicknesses, and interfacial phenomena and modulation doping can be systematically exploited.

More about the speaker:

David C. Johnson is the Rosaria Haugland Foundation Chair in Pure and Applied Chemistry at the University of Oregon. He is the creator of the Graduate Internship program and the Center for Advanced Materials Characterization in Oregon (CAMCOR) – the state of Oregon's 'high tech' extension service, Johnson is also the co-director of the Center for Sustainable Materials Chemistry, an NSF Chemical Innovation Center and the director of  ONAMI's Nanoarchitectures for Enhanced Performance Center.

Johnson's research is at the interface of chemistry and physics focused on controlling materials properties using structure.  His non-traditional approach to chemical synthesis has led to many new materials with unprecedented physical properties.  A recent example is the discovery of a new class of materials material with the lowest thermal conductivity ever reported for a fully dense solid. 

Johnson received his Ph.D. from Cornell in 1983 and worked as a research chemist for DuPont before coming to Oregon in 1986, received the Oregon Academy of Science's Outstanding Scientist Award in 2006.  He has served as a Board Member for the International Thermoelectric Society and is a founding academic member of the Oregon Nanoscience and Microtechnology Institute.- ONAMI. He was a Mercator Fellow of the DFG, the German Research Foundation in 2013 at the University of Freiburg.

Series: Materials Research Lecture Series
Contact: Michelle Aldecua at 626-395-3982 maldecua@caltech.edu
Department of Applied Physics and Materials Science