Our collaborative paper with Dr. Eren Suyolcu of Cornell University and Prof. Gennady Logvenov of Max Planck Institute for Solid State Research is out today in the Journal of Vacuum Science and Technology A. In this work, Eren performed in situ experiments examining the surface reconstructions of Sr-doped La2CuO4 films grown by MBE. Using reflection high energy electron diffraction (RHEED), he tracked how the surface evolves during a shuttered growth routine in ozone and vacuum environments. Ph.D. student Patrick Gemperline applied the principle component analysis and K-means clustering codes developed in our lab by former postdoc Sydney Provence to track the evolution of these surface reconstructions and found that they match quite well to the shuttering times, supporting the conclusions from Eren’s experiments. Our contributions to the work were supported by our AFOSR Young Investigator grant.
Our collaborative work with Prof. Byron Farnum’s group is out today in the Journal of Materials Chemistry A. This work was co-led by Andricus Burton in the Farnum group and Rajendra Paudel in FINO Lab and examines the role of film thickness on catalytic performance of LaFeO3 catalysts for the oxygen evolution reaction. It draws on Prof. Comes’ previous work on the band alignment of LaFeO3 with n-doped SrTiO3 to show how a combination of interfacial electronic reconstruction and the intrinsic high resistivity of LaFeO3 produce a sweet spot for catalysis at ~6 nm thickness. Electron microscopy work from Drs. Steven Spurgeon and Bethany Matthews as well as DFT modeling from Dr. Michel Sassi at Pacific Northwest National Laboratory helped to explain the complex physics and chemistry that occurs at the buried interface and film surface. The work is funded as part of the collaborative NSF grant between our two labs at Auburn.
Our group’s review article in the Journal of Materials Research has been chosen as the winner of the Early Career Scholar in Materials Science Prize by the journal editors with the Materials Research Society! This paper was the result of hard work by graduate students Suresh Thapa, Rajendra Paudel, Miles Blanchet, and Patrick Gemperline, who were co-first authors on it and wrote it during the height of the COVID pandemic in the spring and summer of 2020. Thanks to the many Zoom calls and revisions from everyone it is now a valuable resource for new researchers looking to integrate X-ray photoelectron spectroscopy into film growth! The video above is an interview with Dr. Comes and Prof. Gary Messing of Penn State University, who is the Editor-in-Chief of the journal. The press release from JMR is here.
Congrats to Suresh Thapa for winning the Alabama EPSCOR Graduate Research Scholars fellowship! Our lab is funded by an Air Force Office of Scientific Research (AFOSR) Young Investigator grant that was the first award made with support from the Defense EPSCOR program. Through that award, Suresh is now the first graduate student in Alabama history to receive the GRSP fellowship through Defense EPSCOR funding.
Our collaborative paper with Oak Ridge National Lab has been published in APL Materials. This work focuses on the synthesis of topological parkerite films by MBE and is the first excursion of the FINO Lab into chalcogenide materials. Patrick Gemperline and Tami Isaacs-Smith performed Rutherford backscattering measurements on these samples to confirm film stoichiometry in the self-limited growth regime.
Suresh’s paper on in situ X-ray photoelectron spectroscopy studies of SrTiO3 films grown by hybrid MBE has been published in the Journal of Vacuum Science and Technology A as an Editor’s Pick! This is the first (but not last) paper to report in situ studies of films grown by the novel hybrid MBE method that has been developed for more than a decade. Our unique lab setup was designed specifically to perform this type of work. The article appears in the Special Collection honoring Dr. Comes’ post-doctoral advisor Scott Chambers, who is a leader in in situ XPS, making it particularly appropriate.
Our results show that Sr adatoms on the film surface catalyze the decomposition of the titanium tetraisopropoxide precursor that delivers the titanium cations. Films grown within the stoichiometric growth window have greater than expected concentrations of Sr on the surface, suggesting a partial or complete SrO termination. We collaborated with Prof. Wencan Jin and Dr. Jerzy Sadowski to perform low-energy electron microscopy (LEEM) measurements on films and with Prof. Petra Reinke and Devin Jessup of the University of Virginia to perform scanning tunneling microscopy (STM) on a sample.
These results are part of our ongoing effort to push hybrid MBE into a new regime that enables interfacial studies with different B site cations. Watch for more results over the next year!
Our collaborative paper led by Dr. Tiffany Kaspar of Pacific Northwest National Lab has been published in the Journal of Physics: Condensed Matter! Rajendra Paudel in our group and Tami Isaacs-Smith in the Auburn accelerator lab performed Rutherford back scattering analysis on the films to support the work. These interesting spinel oxides are good candidates for further studies as oxygen evolution and reduction catalysts, which is the focus of our ongoing NSF project in collaboration with Prof. Byron Farnum’s group.
The lab got good news on a new research project, as Dr. Comes was awarded an NSF CAREER award from the Division of Materials Research. The 5 year grant provides $650k in research funding to pursue studies of oxide interfaces and superlattices in 4d and 5d systems grown by hybrid molecular beam epitaxy. You can read about the award here and see the NSF abstract here.
Our new Rigaku SmartLab XRD supported by an NSF Major Research Instrumentation grant was delivered in January and installed in the Chemistry building over the past two weeks. The FINO Lab and our collaborators in the Farnum group have each collected data on the system and now will be going through remote applications training on the system over the coming weeks. More good news for materials research infrastructure here at Auburn!
Miles’ paper on the electronic and structural properties of epitaxial Co1+xMn2-xO4 spinel thin films is now out in the Journal of Physics: Condensed Matter. In this paper we examine the role of the Jahn-Teller distortion in stabilizing the electronic structure of the material as well as Co and Mn ionic coordination and valence. We show the polarization-dependent X-ray absorption studies of these materials and observe a strong polarization dependence in the Mn K edge data due to the Jahn-Teller distortion that has not previously been observed in spinels. Through density functional theory modeling performed by Jonathan Heath and Prof. Marcelo Kuroda at Auburn, Rutherford back scattering performed by Tami Isaacs-Smith, X-ray absorption spectroscopy performed by Dr. Steve Heald at the Advanced Photon Source, along with spectroscopic ellipsometry performed by by Dr. Tiffany Kaspar, X-ray diffraction performed by Dr. Mark Bowden, and scanning transmission electron microscopy performed by Drs. Bethany Matthews and Steven Spurgeon (all at Pacific Northwest National Lab), this was truly a team effort! The paper will be appearing in the 2020 JPCM Emerging Leaders special issue.