Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Z53: Surfaces, Interfaces, and Thin Films: Growth, Processing, and Characterization |
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Sponsoring Units: DMP Room: Mile High Ballroom 2C |
Friday, March 7, 2014 11:15AM - 11:27AM |
Z53.00001: First-principles calculation of oxidation process of SiC substrate Tomoya Ono, Shoichiro Saito The atomic structure of 4H-SiC(0001)/SiO$_2$ interface is still under discussion since the conclusion derived by HRTEM is different from that by SIMS and XPS. The oxidation processes as well as the CO desorption of a SiC substrate are investigated by first-principles calculations. We employ SiC surface and SiC/SiO$_2$ interface models to imitate initial and middle stages of oxidation, respectively. O atoms are inserted between Si-C bond sequentially and the energy gain of the CO desorption is calculated by removing a C atom as a form of CO molecule. We found that the CO desorption becomes preferable when the number of inserted O atoms is three because the perfect SiO$_2$ network remains after the CO desorption and the stress is relaxed by removing the CO molecule from the SiC/SiO$_2$ interface. When C atoms are not removed as CO molecules at the interface, the unoxized Si-C bond remains in SiO$_2$. We also investigate the CO desorption from SiO$_2$. The energy gain of the CO desorption indicates that the CO desorption is unfavorable because the rearrangement of Si-O bonds costs more energy than the CO desorption. Thus, C atoms are immediately emitted from the interface as CO molecules and not kicked out from SiO$_2$. Our results support the conclusion obtained by SIMS and XPS. [Preview Abstract] |
Friday, March 7, 2014 11:27AM - 11:39AM |
Z53.00002: Properties of ZrB$_{2}$ Thin Films Grown by E-Beam Evaporation Robert Lad, David Stewart, Julia Sell, George Bernhardt, David Frankel Zirconium diboride (ZrB$_{2}$) is a candidate material for many high temperature applications because it has a high melting point, high hardness, thermal shock resistance, and metallic conductivity. However, very little work has been reported concerning growth of ZrB$_{2}$ thin films and high temperature oxidation behavior. In this study, ZrB$_{2}$ films with nominal thickness of 200 nm have been deposited using electron-beam evaporation of either ZrB$_{2}$ pellets or elemental B and Zr sources. The ZrB$_{2}$ source yields a film that has a 1:1 Zr:B average composition as measured by X-ray photoelectron spectroscopy, consisting of ZrB$_{2}$ precipitates within an amorphous Zr matrix as determined by X-ray diffraction. Use of elemental B and Zr sources allows precise control of film growth over a range of stoichiometries and yields ZrB$_{2}$ films with much lower oxygen contamination. After annealing ZrB$_{2}$ films to 1200$^{\circ}$C in air, oxidation leads to a loss of B and formation of a textured monoclinic ZrO$_{2}$ phase. Several strategies, including deposition of a thin Al$_{2}$O$_{3}$ capping layer over the ZrB$_{2}$ film are being pursued in an attempt to stabilize the electrically conductive ZrB$_{2}$ phase at high temperature, where it can be used for high temperature electronic devices in harsh environments. [Preview Abstract] |
Friday, March 7, 2014 11:39AM - 11:51AM |
Z53.00003: Understanding nanoscale mechanical properties of materials using ultrafast EUV photoacoustics K. Hoogeboom-Pot, E. Turgut, J. Shaw, J. Hernandez-Charpak, M. Murnane, H. Kapteyn, D. Nardi How do the elastic properties of materials evolve as a nanostructure builds up layer by layer? A host of questions in nanoscience, nanotechnology, quantum dot systems and more rely on an answer to this issue; but our ability to probe mechanical properties is severely constrained at dimensions below 100 nm. With tabletop high harmonic generation (HHG), we overcome these limitations by extending non-destructive visible photoacoustics to extreme ultraviolet (EUV) wavelengths. The short wavelength of EUV light, combined with the coherence and ultrashort pulses of HHG creates a unique and powerful probe of nanostructured materials on their intrinsic length and time scales. We study a series of ultrathin bilayer (10-nm Ni/0-6-nm Ta) nanostructures on SiO$_{2}$ substrates. A femtosecond infrared pulse excites longitudinal acoustic waves (LAWs) within the nanostructures and surface acoustic waves (SAWs) in the substrate. Diffraction of a time-delayed EUV probe pulse monitors the dynamics. LAW resonances are directly related to the bilayer thickness and effective speed of sound; their dependence on Ta-layer thickness reveals that the LAW velocities of both Ni and Ta differ from bulk values. The changing mass of Ta also affects the SAW frequency, allowing us to extract nanoscale densities. [Preview Abstract] |
Friday, March 7, 2014 11:51AM - 12:03PM |
Z53.00004: Heteroepitaxy of group IV-VI nitrides by atomic layer deposition Jeffrey Klug, Nicholas Becker, Carlos Alvarez, Nickolas Groll, Chaoyue Cao, Matthew Weimer, Michael Pellin, John Zasadzinski, Thomas Proslier Heteroepitaxial growth of selected group IV-VI nitrides on various orientations of $\alpha$-Al$_2$O$_3$ and MgO is demonstrated using atomic layer deposition. High quality, epitaxial films are produced at significantly lower temperatures than required by conventional deposition methods. The influence of substrate orientation on film structure and morphology as well as film resistivity and superconductivity are discussed. Transport measurements reveal a reduced room temperature resistivity and increased residual resistance ratio (RRR) for films deposited on lattice-matched substrates compared to polycrystalline samples deposited concurrently on native-oxide Si(001) and fused quartz substrates. [Preview Abstract] |
Friday, March 7, 2014 12:03PM - 12:15PM |
Z53.00005: Transpassive Dissolution of Copper and Rapid Formation of Brilliant Colored Copper Oxide Films Narjes Fredj, T. David Burleigh This investigation describes an electrochemical technique for growing adhesive copper oxide films on copper with attractive colors ranging from gold-brown to pearl with intermediate colors from red violet to gold green. The technique consists of anodically dissolving copper at transpassive potentials in hot sodium hydroxide, and then depositing brilliant color films of Cu$_{\mathrm{2}}$O onto the surface of copper after the anodic potential has been turned off. The color of the copper oxide film depends on the temperature, the anodic potential, the time t$_{\mathrm{1}}$ of polarization, and the time t$_{\mathrm{2}}$, which is the time of immersion after potential has been turned off. The brilliant colored films were characterized using glancing angle x-ray diffraction, and the film was found to be primarily Cu$_{\mathrm{2}}$O. Cyclic voltammetry, chronopotentiometry, scanning electron microscopy, and x-ray photoelectron spectroscopy were also used to characterize these films. [Preview Abstract] |
Friday, March 7, 2014 12:15PM - 12:27PM |
Z53.00006: Annealing Temperature Tuned Structural and Optical Properties of ZnO Sputtered Thin Films Arshad Bhatti, Madiha Sabeen, Malik Abdul-Rehman, Muhammad Bhopal, Awais Ali, Faisal Nasim We report the role of annealing in oxygen environment on the structure and optical properties of zinc oxide (ZnO) thin films grown in oxygen deficient environment. Thin films of two different thicknesses (300 nm and 500 nm) were sputter deposited and annealed from 400 to 800 $^{\circ}$C. X-ray diffraction showed better crystallinity of 500 nm thick films than 300 nm on annealing; however 300 nm films had grown in preferred orientation along the c-axis. The grain sizes increased from 0.1 to 0.45 $\mu $m from the as -- grown to the annealed at 800 $^{\circ}$C, respectively. Raman spectra showed blue shift in E$_{2}$High and 3E$_{2}$LO modes with the increase in the annealing temperature attributed to the enhancement of oxygen vacancies. The A$_{1}$ (TA$+$TO) mode showed red shift due to reduction in structural and surface defects. Room temperature PL showed two bands corresponding to UV and visible were due to band edge emission and defect assisted luminescence and showed distinctively different behavior in the annealed films. [Preview Abstract] |
Friday, March 7, 2014 12:27PM - 12:39PM |
Z53.00007: Formation of a TiO(001) epitaxial thin film on TiO$_2$(110) induced by ion bombardment Oscar Rodriguez, Beatriz Martinez, Irene Palacio, Arantzazu Mascaraque, Jesus Lopez, German Castro, Juan Rubio, Pilar Ferrer, Matteo Monti, Jose Marco, Juan Beltran, Carmen Munoz TiO$_2$ is one of the most studied oxides. This is mainly due to its outstanding photochemical properties. More recently, a growing interest in this oxide has arisen in relationship with resistive switching mechanisms and its possible use in memristors. For all applications low energy ion bombardment has been frequently used to modify or enhace its properties. In this work we show that high doses of ion bombardment tranforms the upper layers of TiO$_2$(110) into epitaxial TiO(001). Surface diffraction and chemical analysis shows the initial transformation of the surface into a disordered suboxide which gives rise to an ordered layer of the monoxide after long irradiation times. This is achieved thanks to the oxygen preferential sputtering, the good registry between the TiO$_2$(110) (rutile) and the TiO(001) (rocksalt) structures (as salso shown by DFT calculations) and the diffusion induced by ion bombardment. To the best of our knowledge, this is the first time that low energy ion bombardment is used to transform the surface of an oxide into another material with a different crystalline structure, while keeping the single crystalline character of the surface. [Preview Abstract] |
Friday, March 7, 2014 12:39PM - 12:51PM |
Z53.00008: Enhanced electrical properties by post thermal nitridation in atomic-layer-deposited HfO$_{2}$ on InP Yu-Seon Kang, Dae-Kyoung Kim, Hang-Kyu Kang, Kwang-Sik Jeong, Mann-Ho Cho, Dae-Hong Ko, Hyoungsub Kim, Jung-Hye Seo, Dong-Chan Kim We investigated the effects of post-nitridation in HfO$_{2}$ thin films grown on InP by atomic layer deposition on the structural, chemical, and electrical properties of the resultant film as well as its thermal stability compared to samples that were only thermally-annealed by comprehensive physical, electrical, and theoretical analyses. By post-deposition annealing under NH$_{3}$ vapor at 600${^\circ}$, an InN layer formed at the HfO$_{2}$/InP interface and ionized NH$_{x}$ was incorporated in the HfO$_{2}$ film. Accordingly, interfacial reactions were effectively suppressed in nitrided HfO$_{2}$/InP by controlling out-diffusion of In or P atoms from the substrate. Nitridation of HfO$_{2}$/InP modulated energy band parameters at the HfO$_{2}$/InP interface, thereby decreasing leakage current. Moreover, the nitridation process significantly suppressed the generation of D$_{it}$ due to controlled diffusion of In and P. DFT calculations showed that In$_{i}$ and P$_{i}$ in HfO$_{2}$ are closely related, with defect states within the band gap of InP. [Preview Abstract] |
Friday, March 7, 2014 12:51PM - 1:03PM |
Z53.00009: Pulsed Laser Deposition Growth of Delafossite (CuFeO$_{2})$ thin films and multilayers Toyanath Joshi, Piero Ferrari, Pavel Borisov, Alejandro Cabrera, David Lederman Owing to its narrow band gap (\textless 2 eV) and p-type conductivity delafossite CuFeO$_{2}$ is attractive for applications in the field of solar energy conversion. Obtaining pure phase CuFeO$_{2}$ thin films, however, is relatively difficult. It is necessary to maintain the lowest possible Cu valency ($+$1) in order to avoid forming the comparably stable spinel compound CuFe$_{2}$O$_{4}$. We present a systematic study of the pulsed laser deposition (PLD) growth conditions for epitaxial (00.1) oriented CuFeO$_{2}$ thin films on Al$_{2}$O$_{3}$ (00.1) substrates. The secondary impurity phase, CuFe$_{2}$O$_{4}$, was removed completely by optimizing the growth conditions. RHEED, XRD and TEM showed that the pure phase delafossite films are highly epitaxial to the substrate. The chemical purity was verified by Raman and XPS. The indirect bandgap of 1.15 eV was measured using infrared reflectivity, and is in agreement with the CuFeO$_{2}$ bulk value. Finally, we discuss the growth and structural characterization of delafossite multilayers, CuFeO$_{2}$/CuGaO$_{2}$. [Preview Abstract] |
Friday, March 7, 2014 1:03PM - 1:15PM |
Z53.00010: Fabrication and Characterization of Metal-Patterned SrCo$_{0.9}$Nb$_{0.1}$O$_{3-\delta}$ Thin Film Cathodes with Well-defined Geometry Iwnetim Abate, WooChul Jung, Sossina Haile A major obstacle to the study of fundamental properties of candidate cathode materials is the morphological complexity of the electrode-electrolyte interface in fuel cells. This complexity prevents a true determination of the catalytic mechanisms. To address this challenge, photolithography patterning technique has been used to make considerably simplified and well-defined electrode geometries. However, the time required for such fabrication is extreme. In this work, we employ a simple shadow-mask-patterning method to fabricate a perovskite oxide-metal composite structure. First, a dense thin film of SrCo$_{0.9}$Nb$_{0.1}$O$_{3}$(SCN) is grown on a Y$_{0.16}$Zr$_{0.84}$O$_{1.92}$ (YSZ) single crystal substrate by pulsed laser deposition. Patterned metal layers are subsequently deposited by DC sputtering with a shadow mask. Thermal stability and electrochemical properties of the fabricated composite cathodes are investigated by optical microscopy, scanning electron microscopy and AC impedance spectroscopy (ACIS). [Preview Abstract] |
Friday, March 7, 2014 1:15PM - 1:27PM |
Z53.00011: Resistive Switching Behaviour of SrCoO$_{x}$ thin films Chang Uk Jung, Octolia Togibasa Tambunan, Bo Wha Lee, Bae Ho Park, Ji-Yong Park, Myung Rae Cho, Yun Daniel Park, Seung Jin Kang, Miyoung Kim, Cheol Seong Hwang Resistance random access memory using metal-oxide insulator-metal structure is attracting considerable attention due to their potential high scalability and low switching current. The resistance switching behavior in many oxides is suggested to associate with local oxygen migration. An insulating brownmillerite SrCoO$_{\mathrm{2.5}}$ has been found to transform topotactically to conducting perovskite SrCoO$_{\mathrm{3}}$, due to the easy oxygen migration even at room temperature. Therefore, the SrCoO$_{x}$ offers a great opportunity to study the switching mechanism based on local oxygen migration. In this report, we succeed to fabricate TE/SrCoO$_{x}$/BE/SrTiO$_{\mathrm{3}}$ devices. The fabrication process covered the 100 nm SCO on 50 nm patterened bottom electrode using pulsed laser deposition. Furthermore, the 80 nm top electrodes by litography patterning was deposited using e-beam evaporator metal deposition. From the TE/SCO/BE memory cell we observed resistance switching with some evidence of conducting filament. We discuss the switching mechanism through the analysis of composition, structure, and dimension of the filaments. [Preview Abstract] |
Friday, March 7, 2014 1:27PM - 1:39PM |
Z53.00012: Sulfide and Oxide-Sulfide Combinatorial Libraries by Co-Sputtering with an Atomic Sulfur Source Joshua Ford, Adam Welch, Christopher Caskey, Bart Van Zeghbroeck, Philip Parilla, David Ginley, Andriy Zakutayev, John Perkins We report a deposition method with improved control over the sulfur content in thin-films through the addition of a radio frequency (RF) solids atom source (cracker) to a multiple-source sputtering system. Co-sputtering from one or two targets provides a compositional gradient across a 2'' substrate. In addition, a temperature gradient orthogonal to the composition gradient is induced. An RF solids cracker is used to provide controllable amounts of activated sulfur during the deposition. The composition gradient, temperature gradient and activated sulfur can be used concurrently to control the composition and phase of the thin films. In proof-of-principle experiments, Cu$_{\mathrm{2}}$S films have been grown from both Cu and Cu$_{\mathrm{2}}$O targets as well as Bi$_{\mathrm{x}}$O$_{\mathrm{y}}$S$_{\mathrm{z}}$ films with tunable oxygen to sulfur ratios from a Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ target. Further, the independent tuning of anion and cation ratios is demonstrated by the growth of BiCuOS. The successful growth of both sulfide and oxide-sulfide compounds demonstrates the viability of this hybrid approach. Finally, this hybrid deposition approach is likely extendable to phosphides and oxide-phosphides. [Preview Abstract] |
Friday, March 7, 2014 1:39PM - 1:51PM |
Z53.00013: Silicon LEDs fabricated using high fluence carbon ion implantation into heated silicon targets Sarah Purdy, John R. McLeod, Himanshu Rai, Andrew Knights, Michael Bradley Fabrication of silicon compatible light emitting diodes (LEDs) is a major goal for modern integrated circuit designers. Ion implantation is a materials processing technique that can be used to engineer materials for this application, by making small to large changes in the stoichiometry at the surface or subsurface of a material. In this study carbon ions were implanted at 20 keV and fluences of 3, 5, 7 and 10 x10$^{16}$ ions/cm$^{2}$ into silicon wafers which were maintained at 400 $^{\circ}$C during the implantation process. The implanted wafers were then annealed at 1000 $^{\circ}$C in flowing nitrogen for 1h. FTIR was used to confirm the formation of SiC. The electronic structure of the implanted and annealed wafers was probed using X-Ray absorption spectroscopy at the silicon L2,3-edge. After treatment, physical vapor deposition was used to apply metal contacts onto the wafers: a semi-transparent Schottky contact (25nm Au) on the implanted surface, and an Ohmic contact (150nm Al) on the back of the wafer. The current-voltage curves and light emission spectra of the resulting Schottky LEDs were collected using a water-cooled electroluminescence testing system. The fabricated LEDs showed turn-on voltages of $\sim$ 2-3V, and the emission spectra showed a broad luminescence band in the orange to infrared (550-900nm) region. The devices are bright, broadband emitters, easily visible to the naked eye and represent one prototype silicon photonics device architecture. [Preview Abstract] |
Friday, March 7, 2014 1:51PM - 2:03PM |
Z53.00014: Thin Film Substrates from the Raman spectroscopy point of view Lev Gasparov, Theo Jegorel, Lars Loetgering, Srimanta Middey, Jak Chakhalian We have investigated ten standard single crystal substrates of complex oxides on the account of their applicability in the Raman spectroscopy based thin film research. In this study we suggest a spectra normalization procedure that utilises a comparison of the substrate's Raman spectra to those of well-established Raman reference materials. We demonstrate that MgO, LaGaO$_{3}$, (LaAlO$_{3}$)$_{0.3}$(Sr$_{2}$AlTaO$_{6}$)$_{0.7}$ (LSAT), DyScO$_{3}$, YAlO$_{3}$, and LaAlO$_{3}$ can be of potential use for a Raman based thin film research. At the same time TiO$_{2}$ (rutile), NdGaO$_{3}$, SrLaAlO$_{4}$, and SrTiO$_{3}$ single crystals exhibit multiple phonon modes accompanied by strong Raman background that substantially hinder the Raman based thin film experiments. [Preview Abstract] |
Friday, March 7, 2014 2:03PM - 2:15PM |
Z53.00015: ABSTRACT WITHDRAWN |
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