Crystal Structure

1. Surface Properties of Transparent Conducting Oxide Materials (TCOs)Thomas O. Mason, Northwestern University, DMR 0602521 Our work investigates the interdependence of crystal structure, defect chemistry and surface properties of TCOs. Crystal Structure Defect Chemistry Surface Properties • Advanced opto-electronic applications (organic light-emitting diodes and photovoltaics) require transparent electrodes with work functions in the 5-6 eV range. • This Materials World Network collaboration between the Mason Group (NU) and the Klein Group (TU-Darmstadt) combines synthesis/defect studies and photoelectron spectroscopy measurements on oxides. • Researchers have learned that there are “right” and “wrong” ways to achieve large work functions in bixbyite TCOs: • “Wrong” involves severe oxidation during synthesis, resulting in de-doped films and/or depleted surfaces. • “Right” involves reduction synthesis, followed by treatments (e.g., intermediate temperature oxidation) for surface dipole modification. Experimental work function vs. Fermi level in TCOs (by UPS).

2. Fostering International CollaborationsThomas O. Mason, Northwestern University, DMR 0602521 Northwestern University Technical University Darmstadt X X • This Materials World Network (MWN) collaboration teams bulk ceramic synthesis/defect chemistry expertise (at NU) with photoelectron spectroscopy expertise (at TUD). • PhD students Steve Harvey (NU) and Christoph Körber (TUD) have each completed two 3-month internship exchanges between the U.S. and Germany. • Multiple joint publications have resulted from this effort, with many more planned.