Increasing thermo-electric conversion efficiency by defect engineering Robert F. Klie , University of Illinois at Chica

1. Increasing thermo-electric conversion efficiency by defect engineeringRobert F. Klie, University of Illinois at Chicago, DMR 0846784 Outcome: A team lead by Professor R.F. Klie combined thin film synthesis, structural characterization and first principles modeling to increase the Seebeck coefficient of Ca3Co4O9, a high-temperature thermoelectric material, by over 30%. Impact: Thermoelectric oxides offer high temperature stability, but the conversion efficiency is limited to ZT<1. Prof. Klie discovered that control over the formation of stacking faults in Ca3Co4O9 thin films can result in doubling the conversion efficiency. Explanation: In cobalt oxide materials with strong electron interactions, the Seebeck coefficient is determined by the Co spin state, and has so far been limited to around 135 μV/K. Through carefully controlled thin film synthesis, atomic-resolution imaging and density functional theory modeling, the team lead by Prof. Klie was able to modify the Co-ion spin state and increase the Seebeck coefficient to 185 μV/K without any increase in the resistivity. Professor Robert F. Klie from the Physics Department at the University of Illinois at Chicago and a recipient of an NSF Faculty Early Career Development (CAREER) award, led the team, which developed these 40 nm thick film of Ca3Co4O9 on different oxide substrates.

2. Revealing the atomic structure of SrTiO3/GaAs interfacesRobert F. Klie, University of Illinois at Chicago, DMR 0846784 Outcome: A team lead by Professor R.F. Klie combined thin film synthesis, structural characterization and first principles investigate the atomic and electronic structures of ultrathin oxide films on compound semiconductor substrates. Impact: If stable, semiconducting oxide films can be stabilized on GaAs supports, hybrid multifunctional oxide-compound semiconductor systems can be developed, combining ferroic properties of oxides with that of compound semiconductors. Explanation: Ultrathin SrTiO3 films on GaAs are sensitive to the high-energy electron beam, and only recent advances in aberration-corrected imaging have allowed low energy characterization, using 80 kV electrons. Ms. Qiao, a 5th year graduate student in Prof. Klie’s group was able to quantify the interfacial atomic structure, and determine the local Ti valence. Using this data, Ms. Qiao developed a model of the SrTiO3/GaAs interface from the early stages of the MBE growth. It was found that Ti diffuses into subsurface GaAs, thus affecting the substrate’s surface reconstruction. Professor Robert F. Klie from the Physics Department at the University of Illinois at Chicago and a recipient of an NSF Faculty Early Career Development (CAREER) award, led the team that developed low energy electron imaging of beam sensitive interfaces.

3. The UIC Journal of Undergraduate ResearchRobert F. Klie, University of Illinois at Chicago, DMR 0846784 Outcome: Professor R.F. Kliepublished the 5th edition of the UIC Journal of Undergraduate Research in May 2012. Impact: The Journal of Undergraduate Research at UIC is a faculty reviewed online publication that is aimed at publishing outstanding research from undergraduate students in the fields of pure and applied sciences, and engineering. The journal promotes research papers by undergraduate students at UIC who are either actively involved in research activities during the academic year or over the summer. Explanation: Working with a 4th year undergraduate student, Mr. Keenan Avers, Professor Klie published the latest issue of the Journal of Undergraduate research at http://jur.phy.uic.edu. This issue contains 12 outstanding papers from undergraduate students who have spend their summer performing research at UIC. The 6th issue will be published in April 2013. Professor Robert F. Klie from the Physics Department at the University of Illinois at Chicago and a recipient of an NSF Faculty Early Career Development (CAREER) award, founded the Journal of Undergraduate Research in 2008, and currently serves as the Editor.