Advances and Discoveries in Non-equilibrium Driven Nanomaterials and Thin Films: Metal Oxide Thin Films
Sponsored by: TMS Functional Materials Division, TMS: Energy Conversion and Storage Committee
Program Organizers: Ritesh Sachan, Oklahoma State University; Srinivasa Rao Singamaneni, University of Texas at El Paso; Amit Pandey, Lockheed Martin Space; Nuggehalli Ravindra, New Jersey Institute of Technology
Tuesday 8:30 AM
February 25, 2020
Room: Solana
Location: Marriott Marquis Hotel
Session Chair: Srinivasa Rao, University of Texas, El Paso; Ravindra Nuggehalli, NJIT
8:30 AM Invited
Controlling Functional Properties in Oxide Nanocomposites via Strain, Defects and Interfaces: Aiping Chen1; 1Los Alamos National Laboratory
Strain, Defects and Interface play critical role in controlling functional properties in complex oxide heterostructures. These parameters have been extensively studied in controlled synthesis to control physical properties. How to control these parameters in more complex two phase vertical heteroepitaxial nanocomposites and how to use these parameters to tailor functionalities in nanocomposites are much less explored. In this talk, I will first talk about the synthesis of a variety of nanocomposite thin films from a perspective of strain, defect and interface. Nanopillar feature size in these two phase nanocomposites has been found to be a critical parameter to control strain, defects and vertical interface density. In the second part of this talk, I will focus on how the to use these parameters to tune the functional properties such as magnetism, magnetotransport and magnetoelectric coupling.
9:00 AM Invited
Stabilization of High-temperature Polymorphs of SrSnO3 at Room Temperature via Epitaxy: Bharat Jalan1; 1University of Minnesota
Through detailed thin film growth, synchrotron x-ray scattering, electronic transport, and first-principles calculations, we will present detailed molecular beam epitaxy (MBE) growth, and epitaxial stabilization of different polymorphs of SrSnO3 (SSO) at room temperature (RT) in thin film form. Compressive strain stabilized the high-symmetry tetragonal phase of SSO at RT, which, in bulk, exists only at temperatures above 1062 K. A mobility enhancement of over 300% in doped tetragonal phase of SSO films compared with the low temperature orthorhombic polymorph was achieved. We will discuss these results in the context of the role of strain, doping and disorder on structure and electronic transport of doped SSO films.Work supported by AFOSR YIP and NSF DMR.
9:20 AM Invited
Effect of Interfacial Strain on the Point-defect Energetics in LaNiOx: Kanishk Rawat1; Dillon Fong2; Dilpuneet Aidhy1; 1University of Wyoming; 2Argonne National Laboratory
In this work, using density functional theory (DFT) calculations, we elucidate the effect of interfacial strain on the formation energy of oxygen vacancies in LaNiOx. Recent experiments show that LaNiO3 undergoes phase transformation to LaNiO2.5 via the creation of oxygen vacancies under varying oxygen partial pressure. We predict that the same phase transformation can be achieved via interfacial strain; this is due to the lowering of the oxygen vacancy formation energy in LaNiO3 under tensile strain. Using DFT calculations, we elucidate the thermodynamics and kinetics of phase transitions in LaNiOx phases which is induced via the ordering and disordering of the oxygen vacancies in LaNiOx. We compare the defect dynamics to the in-situ X-ray Photon Correlation Spectroscopy (XPCS) measurements that captures the dynamics of such structural phase transitions.
9:50 AM
Dynamically Evolving Metastability in an Atomic Hourglass: Temporal Control of the Metal-insulator Transition of VO2 by a Mobile Dopant: Erick Braham1; Diane Sellers1; Ruben Villarreal1; Raymundo Arroyave1; Patrick Shamberger1; Sarbajit Banerjee1; 1Texas A&M University
Continuous modification of metal-insulator transformation temperatures post hoc to synthesis is challenging to access but holds potential for endowing distinctive memory of thermal history as would be useful for neuromorphic computing, chronometry, and sensing. An entirely reversible and dynamical modulation of the phase transformation of VO2 has been observed when using a weakly-coupled mobile dopant. A remarkable time-dependent evolution of the relative phase stabilities of insulating monoclinic (M1) and metallic rutile (R) phases of VO2 in an “hourglass” fashion has been observed as interstitial boron species relax from high-energy sites where they are situated upon a thermally induced phase transition. The relaxation corresponds to a 50°C range of the transition temperature achieved within the same sample as a function of residence time and temperature. The diffusive boron dopant atoms provide a means of attaining a reconfigurable and readable time and thermal history dependent response that derives from intrinsic material properties.
10:10 AM Break
10:30 AM Invited
In-situ and Real Time Chemical Analysis of Complex Oxide Thin Film Surfaces using Pulsed Laser Deposition: Jayakanth Ravichandran; 1
Complex oxides are a class of materials with broad diversity in the structural, chemical and physical characteristics. Pulsed laser deposition (PLD) of complex oxide films has unearthed several of these interesting phenomena and is slowly evolving into a commercially viable technique. The development of high pressure reflection high energy electron diffraction (RHEED) has revolutionized in situ structural characterization during PLD and unleashed atomic scale engineering of oxide heterostructures. In this talk, I will discuss my group’s efforts on implementing an in situ and real time Auger electron spectroscopy for pulsed laser deposition. We have used this method to sense several elements (>25) with monolayer level surface sensitivity. I will also discuss the use of this technique with RHEED to elucidate the dynamics of growth during PLD. I will provide the future outlook for heterostructure engineering and in situ analysis during PLD to discover interesting physical phenomena in complex oxides.
11:00 AM Invited
Recent Advances in Thin Film Thermoelectrics: SnSe and Beyond: Ashutosh Tiwari1; Shrikant Saini1; Paolo Mele2; 1University of Utah; 2Shibaura Institute of Technology
In this talk, we will present recent advances in thin film thermoelectrics. Our particular focus will be on the thermoelectric response of SnSe thin films. These films were grown on r-, a-, and c-plane sapphire substrates by pulsed laser deposition technique and several state of the art characterization techniques were used to characterize the samples. Thermal conductivity of the films was measured by 3ω technique at room temperature. It was observed that the planar orientation of the substrate influences the thermoelectric response of the SnSe thin films quite significantly. The SnSe thin films deposited on r-plane exhibited the lowest thermal conductivity; the highest power factor and ZT values of 1.96 μW/cm.K2 and 0.45, respectively at 800 K. These results are very exciting and have a potential to lead to efficient thin films thermoelectric modules in future.
11:30 AM
Morphological Evolution of Phase-separated Domains in Vapor-deposited Polycrystalline Alloy Films: Rahul Raghavan1; William Farmer1; Kumar Ankit1; 1Arizona State University
Physical vapor deposited nanostructured alloy films yields characteristic self-assembled morphologies with vertical, lateral, or random concentration modulations depending on the deposition rate and temperature. However, the role played by grain boundaries in the formation of any of these nanostructures is not well understood. Here, we employ a phase-field approach that couples composition and orientation order parameters to investigate phase separation and grain boundary evolution in polycrystalline alloy films. Based on parametric studies, we assess the effect of grain coarsening and orientation in the formation of characteristic periodic patterns. Finally, we construct morphology maps to indicate the possibility of new nanostructured variants in polycrystalline films. Insights gained from our investigation will establish the groundwork for new pathways to morphological and grain size control in polycrystalline alloy films.