DATE: Friday, March 20, 2015
TIME: 12:20 pm - 1:30 pm
LOCATION: 301 Campbell Hall
"Oxide Based Hetero-interfaces"
Dr. Alp Sehirlioglu
Department of Materials Science and Engineering
Case Western Reserve University
Oxide based hetero-interfaces exhibit a variety of behavior - tunable conductivity, magnetic scattering, superconductivity - that neither the film, nor the substrate shows separately. The behavior has been related both to intrinsic – electronic reconstruction to avoid polar catastrophe – and extrinsic – point defects – factors. Factors that affect both the magnitude and the presence of a two dimensional conductivity at the interface include surface termination, film thickness, interfacial strain, anion and cation stoichiometry, cation anti-sites and surface adsorbed species. The prototypical pair that shows the tunable electrical conductivity is LaAlO3/SrTiO3 (LAO/STO). LAO was deposited on STO by Pulsed Laser Deposition. Ti-terminated surfaces were prepared by BHF etching and annealing. The parameters of processing include laser fluence, target to substrate distance, deposition temperature and atmosphere. The films can grow layer-by-layer provided optimized deposition conditions and is verified by RHEED. Composition, structure, surface conditions and properties have been characterized. Results include XPS, AFM, XRD, TEM and Hall measurements and include research with collaborators Xuan Gao (Physics/CWRU), Marie Helene Berger (Ecole De Mines) and Andrey Voevodin (AFRL).