Douglas L. Irving
Materials Science & Engineering, NCSU
Enhancing functionality through defect property prediction
Location: EB1 Room 1011
Friday, October 4th 2013 - 11:00 am
The design of advanced materials often depends on the active engineering of defects during synthesis and processing. Eliminating unwanted physical attributes or tailoring the functionality of these materials is often a challenge due, in part, to the interplay between defects within the material. Our research group aids in the efficient design of new materials through integration of predictive simulation into the design toolset. The overall goal of our efforts is to strongly couple theoretical predictions with experiment such that these predictions become part of an integrated materials design framework. In this seminar I will present results from my group's predictive simulations and highlight how these have been coupled to collaborative experimental design efforts. A wide range of materials issues will be touched upon during this presentation. Our simulations of defects in wide band gap semiconductors have helped to identify and eliminate the source of unwanted optical absorption in AlN substrates for deep UV light emitting diodes. Further studies of properties or phenomena related to point defects in wide band gap materials will also be discussed. Our efforts in designing high entropy alloys (HEAs) with high strength and low stacking fault energy (SFE) will also be addressed. Beyond the promise of low SFE materials, HEAs have exhibited many other desirable properties and have led to a new paradigm in metal alloy design. I will also discuss the ability to tune the surface energy of polar oxides as a function of the chemical environment and how this enables the synthesis of low defect oxide films on nitride substrates. Resultant interfaces and residual defects have been investigated by combining the power of STEM imaging, crystal chemistry, and first principles methods. From the combination of these techniques a mechanistic understanding of what drives defect formation in the oxide thin films starting at oxide/nitride hetero-interfaces has been developed. Finally, we will touch upon our efforts to design methods to simulate the in-use environment of an ohmic radio frequency micro-electrical-mechanical system switch. Efforts in our group have been supported by grants from a wide range of sources that include grants from ARO (W911NF1010069), ARPA-E (DE-AR0000299), GE, NSF (DMR-1104930 and DMR-1151568), and ONR (N00014-10-1-0402).