ABSTRACT: Properties and functionality of correlated oxides are intrinsically controlled by the oxygen and cation stochiometries that directly couple to the oxidation state of a transition metal, induce structural and metal-insulator transitions, and govern magnetic and transport properties. In fact, the concentration of oxygen vacancies as controlled by electrochemical potential of oxygen can be considered as a universal order parameter, complementary to classical ferroelectricity, ferromagnetism, and ferroelasticity. Many of the physical phenomena — ranging from magnetoelectric coupling, metal insulator transition, non-volatile polar states — can be controlled directly or indirectly through the vacancy concentration with significantly, often orders of magnitude, higher functional coupling coefficients. Similarly, vacancy dynamics is broadly explored in the context of applications such as solid oxide fuel cells and electrochemical sensors.
Both structural and electronic aspects of these behaviors are currently of interest for energy generation and storage applications, and are uniquely accessible through high-resolution probe-based studies. In this presentation, I will discuss several examples of high-resolution studies of the mechanisms of coupled electronic (metal-insulator, superconductive) and ferroic (ferro- and antiferroelastic, ferro and antiferroelectric) transitions from atomistic to mesoscopic scales enabled by combination of the ex-situ and in-situ Pulsed Laser Deposition growth with atomic resolution Scanning Tunneling Microscopy and Spectroscopy. On the mesoscopic level, we explored experimental signatures of the bias- and strain induced vacancy dynamics in simple oxides including NiO through the high-dimensional scanning probe microscopy measurements, and developed associated Ginzburg-Landau based theoretical description. In La-Sr cobaltites, the high resolution mapping of surface ORR reaction is illustrated. On the atomistic level, we extended the applicability of local crystallographic mapping to scanning tunneling microscopy data, allowing for mapping surface electrochemistry and order parameter fields on the atomic level in manganites, ruthenates, and high-temperature superconductors.
This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences (BES), Materials Sciences and Engineering Division. The research performed in part at the Center for Nanophase Materials Sciences which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
BIO: Sergei V. Kalinin is currently a senior research staff member at Oak Ridge National Laboratory and theme leader for Electronic and Ionic Functionality at the Center for Nanophase Materials Sciences at ORNL, following an Eugene P. Wigner fellow appointment at ORNL (2002?2004). He received his PhD degree in materials science at the University of Pennsylvania in 2002. He is also adjunct faculty at Pennsylvania State University and Sung Kyun Kwan University (South Korea) and professor at the Bredesen Center for Interdisciplinary Research and Education at the University of Tennessee, Knoxville.
His research is focused on local bias-induced phase transitions and polarization dynamics in ferroelectric, multiferroic, and macromolecular systems. In the last several years, he explores local electrochemical and ionic phenomena in solids including battery and fuel cell materials and memristive electronics, with the ultimate purpose of probing electrochemical transformations in solids on a nanometer level of a single-defect level, and atomically-resolved studies of electrochemical and ferroic behaviors on oxide surfaces. The key element of his work is scanning probe microscopy (SPM) of electromechanical and transport phenomena, with specific emphasis of multidimensional and artificial-intelligence?assisted SPM methods. Several of his developments has been adopted and licensed by the SPM industry.
During his academic career, he has been the recipient of the Presidential Early Career Award for scientists and Engineers (PECASE) in 2010, Burton Medal of American Microscopy Society (2010), IEEE-TUFFC Young Investigator Award (2010), the Robert L. Coble (2009) and Ross Coffin Purdy (2003) Awards of American Ceramics Society, AVS Peter Mark Memorial Award (2008), MRS graduate student gold award (2001), and 2 R&D100 awards (2010 and 2008). He organized numerous MRS symposia on SPM and nanoscale electromechanics, is a MRS 2014 Spring meeting organizer, and have served as volume (2012) of MRS Bulletin. He is the author of more than 300 scientific publications and 14 patents and disclosures on different aspects of SPM and ferroelectric materials applications (h = 40). He has also organized a series of international workshops on piezoresponse force microscopy and SPM for energy storage materials, as well as editor of several books including SPM for Energy Research (World Scientific 2013) and SPM of Transport Electromechanical Phenomena (Springer 2006).