Biosketch

Dr. Ryan Comes has been at the University of Delaware since 2024 as an Associate Professor of Materials Science and Engineering. He leads the Films, Interfaces, and Nanostructures of Oxides and Chalcogenides (FINCH) Lab, where the group employs molecular beam epitaxy (MBE) and photoemission spectroscopy (XPS and, soon, ARPES) to examine emergent phenomena in epitaxial thin films and heterostructures. The group focuses on developing new electronic, quantum, and energy materials with atomic precision that will exhibit various functionalities for use in future devices. The use of MBE and XPS/ARPES allows the group to understand phenomena such as interfacial charge transfer, surface and interfacial chemistry, and electronic band alignment across heterojunctions to decouple emergent phenomena from intrinsic defects due to the synthesis process. While past work has focused primarily on complex oxide films, his group will expand in new directions at Delaware to explore chalcogenide materials as well.

Prior to joining Delaware, he was the Thomas and Jean Walter Associate Professor in the Department of Physics at Auburn University from 2016 to 2024. He has received various awards for his research, including a 2020 Air Force Young Investigator Award and a 2021 NSF CAREER Award.  Before beginning his career in academia, he was a Linus Pauling Distinguished Postdoctoral Fellow at Pacific Northwest National Laboratory in the Materials Sciences group from 2013 to 2016. He received his B.S. in Physics and Electrical and Computer Engineering from Carnegie Mellon University in 2008 and his Ph.D. in Engineering Physics from the University of Virginia in 2013.

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Awards

• National Science Foundation CAREER Award (2021)
• Air Force Young Investigator Award (2020)
• Journal of Materials Research Early Career Scholars Prize (2021)
• Journal of Physics: Condensed Matter Emerging Leaders Award (2020)
• Pacific Northwest National Laboratory Linus Pauling Distinguished Postdoctoral Fellowship (2013-2016)
• Materials Research Society Graduate Student Silver Award (2013)
• National Defense Science and Engineering Graduate Fellowship (2010)

Research Interests

Synthesis of 4d and 5d Complex Oxides for Electronic and Quantum Systems

For many years, oxide molecular beam epitaxy focused on elements in the 3d block of the periodic table (i.e. Ti, Fe, Mn) that held promise for functionalities such as ferroelectricity, ferromagnetism, and superconductivity. This part of the field is still going strong, but the initial work on those materials was driven in part by the difficulties of evaporating refractory elements in the 4d and 5d blocks of the table, including Nb, Hf, Ta, and Ir. Our work over the past 5 years has increasingly focused on the development of new ways to make promising electronic and quantum materials such as SrNbO₃, SrHfO₃, and SrIrO₃ using metalorganic precursors to deliver refractory elements via MBE. We are exploring emergent behavior due to interfacial charge transfer in these systems through funding from the National Science Foundation and the Department of Energy using in vacuo X-ray photoelectron spectroscopy and complementary measurements at synchrotron facilities at Brookhaven and Argonne National Labs.

1. Gaurab Rimal, Tanzila Tasnim, Gabriel Calderon Ortiz, George Sterbinsky, Jinwoo Hwang, and Ryan B. Comes. “Strain-dependent Insulating State and Kondo Effect in Epitaxial SrIrO₃ Films,” Physical Review Materials (Letter), 8, L071201, July 2024. DOI: 1103/PhysRevMaterials.8.L071201 Pre-print: arxiv:2404.10909 [cond-mat.mtrl-sci]
2. Gaurab Rimal and Ryan B. Comes. “Development of Complex Oxide Quantum Materials via Molecular Beam Epitaxy,” Journal of Physics D: Applied Physics, Invited review, 57, 193001, May 2024. DOI: 1088/1361-6463/ad2569
3. Sreejith Nair, Zhifei Yang, Dooyong Lee, Silu Guo, Jerzy T. Sadowski, Spencer Johnson, Abdul Saboor, Ryan B. Comes, Wencan Jin, K. Andre Mkhoyan, Anderson Janotti, and Bharat Jalan. “Engineering Metal Oxidation using Epitaxial Strain,” Nature Nanotechnology, 18, 1005-1011, Sep 2023. DOI: 1038/s41565-023-01397-0
4. Sharad Mahatara*, Suresh Thapa*, Hanjong Paik , Ryan Comes, and Boris Kiefer. “High Mobility Two-Dimensional Electron Gas at the BaSnO₃/SrNbO₃ Interface,” ACS Applied Materials and Interfaces, 14, 45025-45031, Oct 2022. DOI: 1021/acsami.2c12195 *Equal contribution Pre-print: arXiv:2206.12028 [cond-mat.mtrl-sci]
5. Suresh Thapa, Sydney R. Provence, Patrick T. Gemperline, Steven R. Spurgeon, Bethany E. Matthews, Sydney L. Battles, Steve M. Heald, Marcelo A. Kuroda, and Ryan B. Comes. “Surface Stability of SrNbO_3+δ Grown by Hybrid Molecular Beam Epitaxy,” APL Materials, 10, 091112, Sep 2022. DOI: 1063/5.0097699

Oxide Films and Heterostructures for Oxygen Evolution and Reduction Catalysis

Photocatalytic and electrocatalytic materials fundamentally rely on the same electronic phenomena that govern semiconductor heterostructures: band alignment at surfaces and interfaces. Transition metal oxides are particularly promising for these kinds of systems because of the tunability of the ionic charge through dopants and interfaces. Our work has previously explored the use of perovskits including LaFeO₃ and LaNiO₃ and spinels including MnFe₂O₄ and Co_xMn_3-xO₄ for use as catalysts. Using X-ray spectroscopy to probe cation charge states and interfacial band alignment, we have been able to explain catalytic performance in films and heterostructures grown by MBE.

1. Rajendra Paudel, Andricus R. Burton, Marcelo A. Kuroda, Byron H. Farnum, and Ryan B. Comes. “Band-Engineered LaFeO₃-LaNiO₃ Thin Film Interfaces for Electrocatalysis of Water,” Journal of Vacuum Science and Technology A, 41, 063207, Dec 2023. DOI: 1116/6.0002987 Pre-print: arXiv:2207.07264 [cond-mat.mtrl-sci]
2. Miles D. Blanchet, Bethany E. Matthews, Steven R. Spurgeon, Steve M. Heald, Tamara Isaacs-Smith, and Ryan B. Comes. “Jahn-Teller-driven Phase Segregation in Mn_xCo_3-xO₄ Spinel Thin Films,” Journal of Vacuum Science and Technology A, 41, 052703, Sep 2023. DOI: 1116/6.0002329 Pre-print: arXiv:2210.16092 [cond-mat.mtrl-sci]
3. Alexandria R. C. Bredar*, Miles D. Blanchet*, Andricus R. Burton, Bethany Matthews, Steven R. Spurgeon, Ryan B. Comes, and Byron H. Farnum. “Oxygen Reduction Electrocatalysis with Epitaxially Grown Spinel MnFe₂O₄ and Fe₃O₄,” ACS Catalysis, 12, 3577-3588, Mar 2022. DOI: 1021/acscatal.1c05172 *Equal contribution Pre-print: arXiv:2111.06229 [cond-mat.mtrl-sci]
4. Andricus R. Burton^*, Rajendra Paudel^*, Bethany Matthews, Michel Sassi, Steven R. Spurgeon, Byron H. Farnum, and Ryan B. Comes. “Thickness Dependent OER Electrocatalysis of Epitaxial LaFeO₃ Thin Films,” Journal of Materials Chemistry A, 10, 1909-1918, Jan 2022. DOI: 1039/D1TA07142D *Equal contribution Pre-print: arXiv:2108.09360 [cond-mat.mtrl-sci]

Data Analytics and Machine Learning for Molecular Beam Epitaxy

One of the greatest challenges of MBE synthesis is controlling film stoichiometry in real time during the growth process. Careful calibration is required before every growth, but feedback during the growth process is limited to electron diffraction data (RHEED images) acquired in real time. Film growers regularly learn what to watch for in the diffraction images during growth, but only after months or years of training. Accelerating that development via big data analytics, machine learning, and, ultimately, artificial intelligence, could revolutionize how epitaxial films are synthesized. Through National Science Foundation funding, we are working on developing new codes to analyze RHEED videos and tie them to post-growth characterization data so that groups around the world will be able to improve their film synthesis capabilities and accelerate the materials development process.

1. Eren Suyolcu, Georg Christiani, Patrick T. Gemperline, Sydney R. Provence, Annette Bussmann-Holder, Ryan B. Comes, Peter A. van Aken, and Gennady Logvenov. “Engineering ordered arrangements of oxygen vacancies at the surface of superconducting La₂CuO₄ thin films,” Journal of Vacuum Science and Technology A, 40, 013214, Jan 2022. DOI: 1116/6.0001473
2. Suresh Thapa, Sydney R. Provence, Devin Jessup, Jason Lapano, Matthew Brahlek, Jerzy T. Sadowski, Petra Reinke, Wencan Jin, and Ryan B. Comes. “Correlating surface stoichiometry and termination in SrTiO₃ films grown by hybrid molecular beam epitaxy,” Journal of Vacuum Science and Technology A, 39, 053203, Sep 2021. DOI: 1116/6.0001159 Pre-print: arXiv:2004.00069 [cond-mat.mtrl-sci]
3. Sydney R. Provence, Suresh Thapa, Rajendra Paudel, Tristan Truttmann, Abhinav Prakash, Bharat Jalan, and Ryan B. Comes. “Machine Learning Analysis of Perovskite Oxides Grown by Molecular Beam Epitaxy,” Physical Review Materials, 4, 083807, Aug 2020. DOI: 1103/PhysRevMaterials.4.083807. Pre-print: arXiv:2004.00080 [cond-mat.mtrl-sci]