This IRG aims to discover the coupling mechanisms between oxygen defects and the transport of phonons, spin and charge at the interfaces of metal oxides, with transformative implications for energy and information technologies. Recent investigations of novel electronic and magnetic properties of complex oxide superlattices have led to tantalizing discoveries. A prime example is the high mobility metallic state found at the interfaces of LaAlO3/SrTiO3 superlattices, composed of materials both of which individually are insulating. The study of the confinement of electrons at these interfaces, and superlattices generally, has had an extraordinary impact on our understanding of important phenomena that can enable high electron mobility devices. Now, a tremendous opportunity exists to achieve further breakthroughs in understanding the role of confinement near oxide interfaces on ionic defect stability and mobility, an area previously defined as nanoionics. Although many structural and electronic factors are known to affect interface properties, we believe oxygen defects play a central role in these phenomena, but their role has thus far been under-explored. While the study of the charge transport behavior of ionic materials at the nanoscale has been pursued for the past decade, this project extends these efforts into entirely new directions by offering means to manipulate and couple the transport of ions, charge, phonons, and magnetic spin.

This ability will enable novel energy-relevant devices such as electrically controlled heat valves, and high efficiency energy conversion platforms such as thermoelectrics and fuel cells, as well as high density and fast memory and logic computing platforms such as memristive and magnetoelectronic devices. Our proposal brings forth two key attributes that set this IRG apart from the existing field of defect studies in oxides. First is the novel and cross-disciplinary merging of nanoionics, phononics, magnetics and electrochemistry, which offers fertile ground for many scientific discoveries by examining the interrelated behavior of ionic defects, charge, spin and phonons. This capacity confers the ability to tune the defect chemistry and ion transport, and to examine their impact in a coupled manner on charge, spin and phonon transport, and magnetic properties. Second is the suite of new capabilities developed by the PIs in this IRG, integrating novel synthesis of nanoscale superlattices characterized by vertical and lateral interfaces, in situ characterization, and multiscale modeling and simulation from the atomic to the mesoscale. By in situ characterization, we mean the ability to perform measurements with very high spatial and temporal resolution in the presence of elevated temperatures (up to ~1000 °C), high electric fields and chemically reactive gases. This approach to identify and interpret, for example, phonon scattering, strain induced oxygen diffusion, and defect induced magnetization at interfaces, presents a powerful predictive capability for designing new materials.





Caroline A. Ross
(group co-leader)



Bilge Yildiz
(group co-leader)
Nuclear Science & Engineering



Geoffrey S. Beach



Gang Chen
Mech E



Harry L. Tuller



Krystyn J. Van Vliet



Strong Electric Fields Tune the Stability of Ionic Defects in Oxides

Microstructure and Magnetic Tuning in Oxygen-Deficient Sr(Ti,Co)O3-δ


Mechanical Stress and Temperature Can Tune the Stability of Electronic Defects in Semiconducting Oxides

Materials Deficient in Oxygen Show Promise in Magnetically Controlled Optical Devices

Functional Oxides Can Be Switched Between Distinct Structures and Properties via Electrochemical Bias

Strain coupling in oxide nano-composites controls magnetism and oxygen exchange kinetics



Chi, Y.T., Youssef, M., Sun, L.X., Van Vliet, K.J., and Yildiz, B. "Accessible switching of electronic defect type in SrTiO3 via biaxial strain." Physical Review Materials, 2(5): Article 055801, May 2018. <DOI: 10.1103/PhysRevMaterials.2.055801>

Tang, A.S., Onbasli, M.C., Sun, X.Y., Ross, C.A. "Thickness-dependent double-epitaxial growth in strained SrTi0.7Co0.3O3−δ films." ACS Applied Materials & Interfaces, 10(8): 7469-7475, February 2018. <DOI: 10.1021/acsami.7b18808>

Lu, Q.Y., Vardar, G., Jansen, M., Bishop, S.R., Waluyo, I., Tuller, H.L., and Yildiz, B. "Surface defect chemistry and electronic structure of Pr0.1Ce0.9O2-δ revealed in operando." Chemistry of Materials, 30(8): 2600-2606, April 2018. <DOI: 10.1021/acs.chemmater.7b05129>

Adepalli, K.K., Yang, J., Maier, J., Tuller, H.L., and Yildiz, B. “Tunable Oxygen Diffusion and Electronic Conduction in SrTiO3 by Dislocation-Induced Space Charge Fields.” Advanced Functional Materials, 27(22): Article 1700243, June 2017. DOI: 10.1002/adfm.201700243

Barbosa, M.S., Suman, P.H., Kim, J.J., Tuller, H.L., Varela, J.A., and Orlandi, M.O. “Gas sensor properties of Ag- and Pd-decorated SnO micro-disks to NO2, H2 and CO: Catalyst enhanced sensor response and selectivity.” Sensors and Actuators B-Chemical, 239: 253-261, February 2017. DOI: 10.1016/j.snb.2016.07.157

Goto, T., Kim, D.H., Sun, X.Y., Onbasli, M.C., Florez, J.M., Ong, S.P., Vargas, P., Ackland, K., Stamenov, P., Aimon, N.M., Inoue, M., Tuller, H.L., Dionne, G.F., Coey, J.M.D., and Ross, C.A. “Magnetism and Faraday Rotation in oxygen-deficient polycrystalline and single-crystal iron-substituted strontium titanate.” Physical Review Applied, 7(2): Article 024006, February 2017. DOI: 10.1103/PhysRevApplied.7.024006

Huang, M., Tan, Aik J., Mann, M., Bauer, U., Ouedraogo, R., and Beach, G.S.D. “Three-terminal resistive switch based on metal/metal oxide redox reactions.” Scientific Reports, 7: Article 7452, August 2017. DOI: 10.1038/s41598-017-06954-x

Youssef, M., Van Vliet, K.J., and Yildiz, B. “Polarizing oxygen vacancies in insulating metal oxides under a high electric field.” Physical Review Letters, 119(12): Article 126002, September 2017. DOI: 10.1103/PhysRevLett.119.126002

Youssef, M., Yildiz, B., and Van Vliet, K.J. “Thermomechanical stabilization of electron small polarons in SrTiO3 assessed by the quasiharmonic approximation.” Physical Review B, 95(16): Article 161110, April 2017. DOI: 10.1103/PhysRevB.95.161110


Moors, M., Adepalli, K.K., Lu, Q.Y., Wedig, A., Baumer, C., Skaja, K., Arndt, B., Tuller, H.L., Dittmann, R., Waser, R., Yildiz, B., and Valov, I. “Resistive switching mechanisms on TaOx and SrRuO3 thin-film surfaces probed by scanning tunneling microscopy.” ACS Nano, 10(1): 1481-1492, January 2016. DOI: 10.1021/acsnano.5b07020

Lu, Q.Y., Chen, Y., Bluhm, H., and Yildiz, B. “Electronic structure evolution of SrCoOx during electrochemically driven phase transition probed by in situ x-ray spectroscopy.” Journal of Physical Chemistry C, 120(42): 24148-24157, October 2016. DOI: 10.1021/acs.jpcc.6b07544

Chen, Y., Ojha, S., Tsvetkov, N., Kim, D.H., Yildiz, B., and Ross, C.A. “Spinel/perovskite cobaltite nanocomposites synthesized by combinatorial pulsed laser deposition.” Crystengcomm, 18(40): 7745-7752, 2016. DOI: 10.1039/c6ce01445c

Choi, S.-J., Chattopadhyay, S., Kim, J.J., Kim, S.-J., Tuller, H.L., Rutledge, G.C., and Kim, I.D. “Coaxial electrospinning of WO3 nanotubes functionalized with bio-inspired Pd catalysts and their superior hydrogen sensing performance.” Nanoscale, 8(17): 9159-9166, 2016. DOI: 10.1039/c5nr06611e

Choi, S.J., Kim, S.J., Cho, H.J., Jang, J.S., Lin, Y.M., Tuller, H.L., Rutledge, G.C., and Kim, I.D. “WO3 nanofiber-based biomarker detectors enabled by protein-encapsulated catalyst self-assembled on polystyrene colloid templates.” Small, 12(7): 911-920, February 2016. DOI: 10.1002/smll.201502905

Khalil, A., Kim, J.J., Tuller, H.L., Rutledge, G.C., and Hashaikeh, R. “Gas sensing behavior of electrospun nickel oxide nanofibers: Effect of morphology and microstructure.” Sensors and Actuators B-Chemical, 227: 54-64, May 2016. DOI: 10.1016/j.snb.2015.12.012

Kim, S.J., Choi, S.J., Jang, J.S., Kim, N.H., Hakim, M., Tuller, H.L., and Kim, I.D. “Mesoporous WO3 nanofibers with protein-templated nanoscale catalysts for detection of trace biomarkers in exhaled breath.” ACS Nano, 10(6): 5891-5899, June 2016. DOI: 10.1021/acsnano.6b01196

Koo, W.T., Choi, S.J., Kim, S.J., Jang, J.S., Tuller, H.L., and Kim, I.D. “Heterogeneous sensitization of metal-organic framework driven metal@metal oxide complex catalysts on an oxide nanofiber scaffold toward superior gas sensors.” Journal of the American Chemical Society, 138(40): 13431-13437, October 2016. DOI: 10.1021/jacs.6b09167

Santiso, J., Roqueta, J., Bagues, N., Frontera, C., Konstantinovic, Z., Lu, Q.Y., Yildiz, B., Martinez, B., Pomar, A., Balcells, L., and Sandiumenge, F. “Self-arranged misfit dislocation network formation upon strain release in La0.7Sr0.3MnO3/LaAlO3(100) epitaxial films under compressive strain.” ACS Applied Materials & Interfaces, 8(26): 16823-16832, July 2016. DOI: 10.1021/acsami.6b02896

Tsvetkov, N., Lu, Q.Y., Sun, L.X., Crumlin, E.J., and Yildiz, B. “Improved chemical and electrochemical stability of perovskite oxides with less reducible cations at the surface.” Nature Materials, 15(9): 1010-1016, September 2016. DOI: 10.1038/NMAT4659


Wedig, A., Luebben, M., Cho, D.-Y., Moors, M., Skaja, K., Rana, V.,  Hasegawa, T., Adepalli, K., Yildiz, B., Waser, R. and Valov, I. “Nanoscale cation motion in TaOx, HfOx, and TiOx memristive systems.” Nature Nanotechnology, 10(9): 729-824, September 2015. DOI: 10.1038/NNANO.2015.221

Lu, Q. and Yildiz, B. “Voltage-Controlled Topotactic Phase Transition in Thin-Film SrCoOx Monitored by In Situ X‐ray Diffraction.” Nano Letters, 16: 1186−1193, December 2015. DOI: 10.1021/acs.nanolett.5b04492

Wedig, A., Luebben, M., Cho, D.-Y., Moors, M., Skaja, K., Rana, V.,  Hasegawa, T., Adepalli, K., Yildiz, B., Waser, R. and Valov, I. “Nanoscale cation motion in TaOx, HfOx, and TiOx memristive systems.” Nature Nanotechnology, 10(9): 729-824, September 2015. DOI: 10.1038/NNANO.2015.221