|
Detail: |
Dr. Yingge Du is a Sr. Research Scientist at the Pacific Northwest National Laboratory (PNNL), USA. He served as the technical lead in designing, building, and testing of a new MBE system and developed the next-generation atom flux sensors for accurate flux sensing and control during thin film deposition. He is also PI and Co-PI on PNNL and DOE funded research programs.
Abstract：Oxygen vacancies are often present in complex oxides as point defects and their effect on the electronic properties of the oxides is typically uniform and isotropic. Exploiting oxygen deficiency in order to generate controllably, novel structures and functional properties remains a challenging goal. We show that in MBE grown TiO2, WO3, and SrCrO3 single crystalline thin films, oxygen defects govern their surface chemical reactions, bulk Li intercalation processes, and electronic properties, respectively. In particular, epitaxial strontium chromite films can be transformed, reversibly and at low temperature, from the cubic metallic perovskite SrCrO3 to the rhombohedral semiconducting SrCrO2.8. Oxygen vacancies aggregate and give rise to ordered arrays of {111}-oriented SrO2 planes interleaved between layers of tetrahedrally-coordinated Cr4+ and separated by ~1 nm. First-principle calculations provide insight into the origin of the stability of such nanostructures and, consistent with the experimental data, predict that the barrier for oxide ion diffusion along these quasi-2D nanostructures is a lot lower than that in the cubic SrCrO3 – a property of considerable importance in, for example, solid oxide fuel cells. |
