Interface-Engineered Complex Oxide Heterostructures with Designable Physical Properties

Investigations were made in attempts to improve the compositional and structural quality of SrTiO3 (STO) thin films as grown by the Gen 2 MOCVD (CoNotS) system at the United States Army Research Laboratory (ARL) in Aberdeen Proving Ground, MD, as well as to increase the homogeneity over sample area. In all of the aforementioned aspects, sample quality was notably improved by modifications to both the hardware and growth parameters. This research is performed at ARL under the guidance of Melanie Will-Cole, Sr. Research Physical Scientist. The effect of A and B-site substitution to perovskite cobaltate thin films on the diffusion and surface exchange kinetics were investigated for various doping agents. Enhancement of the diffusion activity was observed, as well as a tuning of the temperature of peak activity. Observed oscillatory behavior in the resistance response under oxidation reactions is theorized to indicate a layer-by-layer oxygen vacancy exchange diffusion mechanism of charge carrier ion species. The obtained results suggest that LnBCO materials, in particular those with properties tuned by A and B-site fractional substitution such as Pr(Ba0.5,Sr0.5)(Co1.5,Fe0.5)5.5+d (PBSCFO) are excellent candidates for the development of low or intermediate temperature energy conversion devices and gas sensor applications.