Invited Talk at Electronic Materials and Application 2017

Dr. Comes will be presenting an invited talk on his work on the LaFeO3/n-SrTiO3 interface and on LaCrO3-SrTiO3 superlattices at the American Ceramics Society Electronic Materials and Applications conference this week at 9 am Friday, Jan 20. Portions of this work have been published in Physical Review Letters, Chemistry of Materials, and Advanced Materials Interfaces in the past year. We’re looking forward to a great conference!

Work on LaFeO3/n-SrTiO3 Interface Published in Physical Review Letters

Dr. Comes’ work on the LaFeO3/n-SrTiO3 interface has been published in Physical Review Letters here! In this work, which was done at Pacific Northwest National Laboratory in collaboration with Dr. Scott Chambers, we show that the band alignment between LaFeO3 (LFO) and Nb-doped SrTiO3 (STO) is relatively insensitive to the interfacial termination. We synthesized a series of LFO films on SrO- and TiO2-terminated STO to examine how changing the interface dipole affects band alignment, which is key to enabling next-generation photovoltaics and photocatalysts. Using in situ x-ray photoelectron spectroscopy, we were able to measure the valence band alignment and then determine the conduction band alignment through our measurement of the LFO band gap with ellipsometry. These results help to address some confusing results in the literature and will hopefully generate further study down the road.

Presenting at AVS Meeting and Southeastern Section of APS

Superlattice EELSDr. Comes will be presenting at the AVS meeting this Tuesday, Nov. 8, in Nashville, TN, discussing collaborative work with Prof. Chuck Fadley at UC Davis from his time at PNNL studying SrTiO3-LaCrO3 superlattices with standing-wave angle-resolved x-ray photoelectron spectroscopy. After the time in Nashville, he will move on to Charlottesville, VA to give an invited talk at the Southeastern section of the American Physical Society annual meeting on Friday, Nov. 11. This talk will focus on work exploring the SrTiO3-LaFeO3 interface that will be published soon in Phyiscal Review Letters and is available on arXiv now.

Paper on NdTiO3-SrTiO3 Interfaces Published in Physical Review Letters

A collaborative paper led by Bharat Jalan’s group at the University of Minnesota and our group at Pacific Northwest National Lab
exploring the effects of different defects at the interface between SrTiO3 (STO) and NdTiO3 (NTO) on the electronic behavior of the two-dimensional electron gas in this system has been published in Physical Review Letters! We find that the electronic behavior is highly dependent on both Nd:Ti stoichiometry and on the level of oxidation in the NTO layer. Somewhat surprisingly, our x-ray photoelectron spectroscopy measurements and density functional theory analysis indicate that oxygen interstitials may diffuse from the surface into the bulk of the NTO film, changing the Ti formal valence from 3+ to 4+. This has drastic effects on the electronic behavior of the conducting interface between STO and NTO, which will help us understand how to better engineer these materials going forward.