Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session S45: Oxides Films, Coatings, and Related ApplicationsFocus Session
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Sponsoring Units: DCMP Chair: Robert Klie, Univ of Illinois - Chicago Room: BCEC 211 |
Thursday, March 7, 2019 11:15AM - 11:27AM |
S45.00001: Low loss amorphous Ta2O5 coatings grown by reactive sputtering for dielectric mirrors used for gravitational wave detection Keerti Shukla, Manel Molina-Ruiz, Matt Abernathy, Alena Ananyeva, Riccardo Bassiri, Martin Fejer, Eric Keith Gustafson, Xiao Liu, Ashot Markosyan, Thomas Metcalf, Gabriele Vajente, Frances Hellman The ability of LIGO and others in the gravitational wave community to detect astronomical events relies on the quality of optical mirrors used in interferometers. A lot of effort is devoted to reduce optical absorption and mechanical loss in the layers that make up the mirror coatings. Amorphous tantala is of interest as the high index of refraction layer but contributes the most to overall mechanical loss. The mechanisms that lead to mechanical loss must be understood in order to minimize the losses. |
Thursday, March 7, 2019 11:27AM - 11:39AM |
S45.00002: WITHDRAWN ABSTRACT
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Thursday, March 7, 2019 11:39AM - 11:51AM |
S45.00003: Understanding the role of carbon in active trap centre formation in porous alumina for ion beam dosimetry SANGITA BHOWMICK, saptarshi pal, DIP DAS, Vipin kumar Singh, saif khan, rene huebner, sudipto roybarman, dinakar Kanjilal, Aloke Kanjilal In recent days, due to increased use of hadron therapy for cancer and tumor treatment, precise online dose monitoring is an important issue for safety purpose. Regarding hadron therapy, recently carbon ion beam with high Linear Energy Transfer (LET) is found to be more effective than the photon beams. Among several known TL/OSL oxides phosphors, C-doped alumina (Al2O3) is favorable for radiation dosimetry, especially in medical field due to its tissue equivalent in terms of radiation absorption, simple glow curve, and high sensitivity. A facile approach to improve thermoluminescence sensitivity of electrochemically anodized porous Al2O3 (AAO) is presented by introducing carbon ions for ion beam dosimetry. Initially, ion implantation technique has been carried out for Carbon doping in AAO in controlled manner. HAADF-STEM, EDS mapping, SEM studies reveal the evolution of a porous structure followed by the carbon distribution upto 200nm. However, the evolution of optically active F+ centres with increasing ion fluence has been examined by photoluminescence investigation at room temperature and thermoluminescence (TL) measurement while the chemical nature of such defect centres has been extracted by depth dependent XPS analysis. |
Thursday, March 7, 2019 11:51AM - 12:03PM |
S45.00004: Interface-engineered hole doping in Sr2IrO4/LaNiO3 heterostructure Fangdi Wen, Xiaoran Liu, Qinghua Zhang, Mikhail S Kareev, Banabir Pal, Yanwei Cao, John William Freeland, Alpha N'Diaye, Padraic Shafer, Elke Arenholz, Lin Gu, Jak Chakhalian The relativistic Mott insulator Sr2IrO4 is known for the Jeff = 1/2 Mott insulating state which closely resembles the electronic structure of parent compounds of superconducting cuprates. Here, by means of interface engineering of the Sr2IrO4/LaNiO3 heterostructure, the hole-doped phase of Sr2IrO4 has been realized with a markedly higher doping level close to 10%. X-ray absorption studies at Ni L2 edge confirmed that 5d electrons from Ir sites are transferred onto Ni sites leading to the formation of a high spin Ni2+ state. Despite the large amount of doping, Sr2IrO4/LaNiO3 heterostructure shows a non-metallic behavior but a narrower band gap compared to the bulk Sr2IrO4. This implies strong electronic reconstruction at the interfaces. These findings highlight a powerful utility of interfaces to realize emerging electronic states of the Ruddlesden-Popper phases of Ir-based oxides. |
Thursday, March 7, 2019 12:03PM - 12:15PM |
S45.00005: Over 100-THz Bandwidth Selective-Difference-Frequency Generation at LaAlO3/SrTiO3 Nanojunctions Lu Chen, Erin Sutton, Hyungwoo Lee, Jungwoo Lee, Jianan Li, Chang-Beom Eom, Patrick Irvin, Jeremy Levy The ability to combine continuously-tunable narrow-band terahertz (THz) generation that can access both far-infrared and mid-infrared regimes, with nanometer-scale spatial resolution, holds great potential for uncovering the underlying light-matter interactions as well as realizing selective control of rotational or vibrational resonances in nanoscale objects. Here, we report selective difference frequency generation with over 100 THz bandwidth through femtosecond optical pulse shaping. The THz emission is generated at nanoscale junctions at the interface of LaAlO3/SrTiO3 defined by conductive atomic force microscope lithography, with the potential to perform THz spectroscopy on individual nanoparticles or molecules. Numerical simulation of the time-domain signal helps to identify different contributing components for the THz generation. These results transform the LaAlO3/SrTiO3 interface into a promising platform for integrated lab-on-chip devices. |
Thursday, March 7, 2019 12:15PM - 12:27PM |
S45.00006: Morphological anisotropy and mosaicity in epitaxially grown VO2 films Anatoly Shabalin, Elihu Anouchi, Martin Holt, Amos Sharoni, Oleg Shpyrko Epitaxially grown films of VO2 are one of the most promising materials for oxide electronics due to a very convenient temperature and remarkable controllability of the insulator-to-metal phase transition (IMT) by doping, strain, photo excitations or applying an electric field. Scaling the IMT-based devices down to submicron size is a technological challenge because of the high variability of the resulted functional characteristics from device to device. Our work focuses on the structural and morphological origins of such variations. |
Thursday, March 7, 2019 12:27PM - 12:39PM |
S45.00007: Preparation and X-Ray Diffraction Study of Strongly Oriented Thin Films with Potential Magnetoelectric Effect Radomir Kuzel, Josef Bursik, Robert Uhrecky, Miroslav Soroka, Jan Prokleska Thin films of M, Y and Z hexagonal ferrites with a potential of magnetoelectric (ME) effect were prepared by chemical solution deposition method and processing parameters were tested and optimized. Several substrates were used, and different substrate/seeding layer/ferrite layer architectures were proposed to get strong preferred grain orientation. The films were studied by X-ray diffraction (XRD), AFM and EBSD. Lattice parameters, out-of-plane and in-plane grain orientations, crystallite sizes, microstrains and residual stresses were obtained by different XRD symmetric and asymmetric scans and their combinations. |
Thursday, March 7, 2019 12:39PM - 12:51PM |
S45.00008: Magnetic Scattering studies of rare earth thin film spiral antiferromagnetics Stjepan Hrkac, Rajasekhar Medapalli, Peter Oliver Sprau, Eric Fullerton, Oleg Shpyrko Understanding complex magnetic interactions by studying mesoscale magnetism creates and enhances technological applications. Holmium (Ho) is a rare-earth magnetic element with high magnetic moment per atom, and in bulk exhibits exotic magnetic properties such as a spiral antiferromagnetic state, the formation of chiral domains, or Spin-Slips. |
Thursday, March 7, 2019 12:51PM - 1:03PM |
S45.00009: SrTiO3 surfaces prepared by HCl etching Camille Bean, Miro Furtado, Jason D. Hoffman, Tatiana Webb, Christian Matt, Jennifer Hoffman In molecular beam epitaxy synthesis of crystalline heterostructures, the quality of the substrate surface is crucial. The substrate not only provides a structural template for the deposited film, but for many new materials which are just a few atomic layers thick, the interaction with the substrate determines the emergent electronic properties. SrTiO3 substrates are widely used for growth of complex oxides and superconducting FeSe, but reproducible surface preparation remains challenging. The standard recipe employs a buffered hydrofluoric acid etch, but it has been shown that this step results in significant fluorine replacement of oxygen near the surface of SrTiO3 [1]. Here we characterize halogen doping from use of an alternative etchant, hydrochloric acid. |
Thursday, March 7, 2019 1:03PM - 1:15PM |
S45.00010: High Temperature Oxidation of Amorphous Zr-B-C-N Thin Films Grown by Electron Beam Evaporation Morton Greenslit, Morgen Benninghoff, Robert J Lad Boron carbonitride films have been shown to yield enhanced hardness and oxidation resistance, making them potentially attractive as protective coatings for high temperature applications. Most previous work has focused on thick films (>1μm) grown by magnetron sputtering. In this study, 200 nm thick ZrBCN films with a range of stoichiometries were grown on r-sapphire substrates at 850oC using e-beam evaporation of ZrC and B sources in a nitrogen plasma. As-deposited films were found to be amorphous by XRD, and the nitrogen content was relatively constant independent of ZrC or B evaporation rates. XPS analysis of the films after air annealing over the range 500-800oCshowed that B and N were entirely depleted at the surface, while ZrO2 grains nucleated within the amorphous film matrix. XRD showed the formation of a tetragonal-ZrO2 phase at 600oC that became replaced by a monoclinic-ZrO2 phase at 800oC as the ZrO2 grains grew in size. SEM analysis showed film delamination and cracking during high temperature oxidation to relieve film stress. The oxidation resistance of the 200 nm ZrBCN films is much less than reported for thicker sputtered films, indicating that the oxidation resistance mechanism is strongly dependent on film thickness. |
Thursday, March 7, 2019 1:15PM - 1:27PM |
S45.00011: Reduction of Stress in Dual Ion Beam Sputtered Ta2O5 and SiO2 Optical Interference Coatings Emmett Randel, Aaron Davenport, Carmen Susana Menoni We studied the mechanical and optical properties of tantalum pentoxide (Ta2O5) and silicon dioxide (SiO2) films prepared by dual ion beam sputtering with the goal to realize thin films with a stress below 0.3 GPa. It is shown that the use of a low energy assist beam consisting of oxygen and argon species results in a Ta2O5 film with a stress below 100 MPa and a SiO2 film with a stress below 250 MPa. Using photothermal common path interferometry (PCI), spectrophotometry, and ellipsometry, it is shown that these films are suitable for use in interference coatings. |
Thursday, March 7, 2019 1:27PM - 1:39PM |
S45.00012: Properties of CCTO, a High Dielectric Constant Material Parveen Kumar, D. C. Agrawal CaCu3Ti4O12 (CCTO) shows an extremely high dielectric constant, which, in contrast to ferroelectrics like BaTiO3, is nearly constant in a broad temperature range. Thus, this material has attracted tremendous attention due to its possible applications, e.g., for enhancing the performance of capacitive electronic elements. We used a simple Sol-Gel technique and established a novel composition of CCTO with high dielectric constant, and fabricated stable and reliable thin films. We have successfully incorporated silver nanoparticle in CCTO thin films. The conducting metal particles dispersed in a dielectric matrix are known to increase the effective dielectric constant of the medium. Based on these novel materials, we developed tunable multilayer capacitor with high dielectric constant. |
Thursday, March 7, 2019 1:39PM - 1:51PM |
S45.00013: Influence of Assist Ion Bombardment on Mechanical Loss of Amorphous Tantala Thin Films for Gravitational Wave Interferometers Le Yang, Emmett Randel, Gabriele Vajente, Alena Ananyeva, Eric Keith Gustafson, Ashot Markosyan, Martin Fejer, Carmen Susana Menoni Thermal noise in high-reflectivity coatings is critical for improving the sensitivity of future gravitational wave detectors. Amorphous tantala (Ta2O5) thin film, used as high-index material, with lower mechanical loss is expected as one solution to further reduce the coating thermal noise. The material is also regarded as promising candidate for use in resistance random access memory as well as optical applications. In this work, amorphous tantala thin films have been deposited by reactive ion beam sputtering with assist Ar+ and Xe+ ion bombardment to investigate the effect of ion-induced surface diffusion on coating's mechanical and structural properties. The results show that the atomic structure of ion bombarded tantala thin films remain amorphous and their composition is mostly stoichiometric. The mechanical loss of ion-bombarded tantala coatings shows no significant improvement compared to non-bombarded samples. The coating loss angle of tantala is insensitive to ion dose or ion mass. An analysis based on surface diffusivity suggests that the ion-assisted surface diffusivity may be insignificantly modified under the current typical deposition conditions. |
Thursday, March 7, 2019 1:51PM - 2:03PM |
S45.00014: TiO2 doped Ta2O5 coatings grown by biased target ion beam deposition for gravitational wave detectors Mariana Fazio, Gabriele Vajente, Alena Ananyeva, Eric Keith Gustafson, Carl Lévesque, François Schiettekatte, Ashot Markosyan, Riccardo Bassiri, Martin Fejer, Carmen Susana Menoni Advanced LIGO employs as end masses high reflectance mirrors of alternating layers of SiO2 and Ta2O5 doped with 25% of TiO2. Doping Ta2O5 with 25% TiO2 decreased the mechanical loss which increased the sensitivity of the detector, but the physical reasons of this are still unknown. In this work we studied thin films of Ta2O5 doped with different TiO2 concentrations grown by biased target ion beam deposition to evaluate the effect of doping in the mechanical loss and to search for high index materials with improved performance for the upcoming upgrade of LIGO and future detectors. |
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