Bulletin of the American Physical Society
83rd Annual Meeting of the APS Southeastern Section
Volume 61, Number 19
Thursday–Saturday, November 10–12, 2016; Charlottesville, Virginia
Session G2: Films and Surfaces |
Hide Abstracts |
Chair: Michel Pleimling, Virginia Tech University Room: Salon C |
Friday, November 11, 2016 10:45AM - 10:57AM |
G2.00001: Parallel Upper Critical Field Slope in Niobium Thin Films: Comparison to Theory Phillip Broussard, Angela Hunziker, Amy Davis Thin films of niobium deposited by magnetron sputtering have been characterized by critical field measurements with the magnetic field applied parallel to the film plane. Films with thicknesses varying from 17 to 52 nm were grown using various deposition conditions so that the ``dirtiness'' parameter $\lambda_{\mathrm{tr}}=\xi/\ell_{\mathrm{tr}}$ (where $\xi=\hbar v_{F}/(2\pi k_{B}T_{c0})$ is an effective coherence length, $T_{c0}$ is the zero field critical temperature, and $\ell_{\mathrm{tr}}$ is the elastic mean free path) varied from 2 to 11. The ratio of film thickness to $\xi$ varied from 0.4 to 1.4. The expected linear dependence of $B^{2}$ vs $T$ is observed, and the values of the slopes of these plots are compared to the predictions of Hara and Nagai (J. Phys. Soc. Japan, {\bf 63}, 2331 (1994)). We see a systematic lack of agreement between theory and experiment, with experimental values lower than the theoretical predictions, even after including possible strong coupling corrections. [Preview Abstract] |
Friday, November 11, 2016 10:57AM - 11:09AM |
G2.00002: Experimental and Modeling Study of Thickness Dependence of Amorphous TbFeCo Compensation Xiaopu Li, Chung T. Ma, Howard Sheng, S. Joseph Poon Amorphous TbFeCo thin films with strong perpendicular magnetic anisotropy are found to exhibit significant thickness-dependent ferrimagnetic compensation. The compensation temperature varies over 100 K for film thickness ranging from 15 to 100 nm. Amorphous structure with depth-dependent short-range order has been proposed to explain this thickness-dependence. A micromagnetic model has been built based on an ab-initio atomistic calculation by molecular dynamics of TbFe metallic glass. Micromagnetic simulation with Landau-Lifshitz-Bloch equation agrees quantitatively with the experimental results. Our study provides a way of tuning ferrimagnetic compensation through thickness control, which is useful for application of amorphous TbFeCo thin film in ultrafast spintronics. [Preview Abstract] |
Friday, November 11, 2016 11:09AM - 11:21AM |
G2.00003: Mircomagnetic Simulation of Ferrimagnetic TbFeCo Films with Exchange Coupled Nanophases. Chung Ma, Xiaopu Li, Joseph Poon, Jiwei Lu Amorphous ferrimagnetic TbFeCo thin films are found to exhibit exchange bias effect near the compensation temperature by magnetic hysteresis loop measurement$^{\mathrm{1}}$. The observed exchange anisotropy originates from phase separations distributed within the films. Using micromagnetic simulation, we develop a computational model to study exchange bias effect in phase-separated TbFeCo$^{\mathrm{2}}$. Two types of cells with different Tb concentration are distributed within the simulated space to obtain a heterogeneous structure. Each cell contains separated Tb and FeCo components, forming two antiferromagnetically coupled sublattices. This model is able to demonstrate exchange bias effect in agreement with experiment. Furthermore, using this model, one can explore ferrimagnetic/ferromagnetic and ferrimagnetic/ferrimagnetic systems, and develop exchange bias materials with desirable properties for applications at room temperature. References: 1. Xiaopu Li, Chung T. Ma, Jiwei Lu, Arun Devaraj, Steven R. Spurgeon, Ryan B. Comes and S. Joseph Poon, Appl. Phys. Lett. 108, 012401 (2016). 2. Chung T. Ma, Xiaopu Li and S. Joseph Poon, J. Magn. Magn. Mater. 417, 197 (2016). [Preview Abstract] |
Friday, November 11, 2016 11:21AM - 11:33AM |
G2.00004: Relaxation dynamics of interacting skyrmions in thin films Bart Brown, Michel Pleimling Magnetic skyrmions are topologically protected spin textures which were recently observed in certain chiral magnets such as MnSi. Skyrmions can be moved by very low current densities (five orders of magnitude less than typical magnetic domain walls) which makes them very promising in spintronics applications. A thorough understanding of the relaxation processes for systems of interacting skyrmions far from equilibrium could prove invaluable in real world applications but is currently lacking in the literature. The dynamics are described by the Landau-Lifshitz-Gilbert (LLG) equation, however, simulating many interacting skyrmions by solving the LLG equation is computationally infeasible. In order to explore these relaxation processes, we employ a suitable two-dimensional particle based model derived from Thiele's approach. We find that the scaling properties of the density-density correlation function depend non-trivially on the magnitude of the Magnus force, which points perpendicular to the skyrmion velocity in the plane, and on the Gaussian noise term. [Preview Abstract] |
Friday, November 11, 2016 11:33AM - 11:45AM |
G2.00005: Photostructural changes as a function of photon energy and intensity in thermally deposited As-S thin films Justin Oelgoetz, Joshua Allen, Jonathan Bunton, Laura Nichols, Caithleann Thomas, Roman Golovchak, Andriy Kovalskiy, Miroslav Vlcek Thermally deposited chalcogenide glass thin films (ChGF) can undergo photo-structural changes when exposed to light. The mechanism likely includes processes such as photo-structural relaxation, bond switching and defect formation on both the surface and inside of ChGF. Experimental studies show that light with energies close to the band gap does not modify chemical composition of the surface, but induces simple photopolymerization reactions. UV light with energy above the bandgap significantly increases S/As ratio on the surface by forming a S-rich layer under both environmental conditions. Based on the Density functional calculations presented in this poster, we propose that photovaporization of both oxide and non-oxide cage-like molecules is responsible for the observed effect. [Preview Abstract] |
Friday, November 11, 2016 11:45AM - 11:57AM |
G2.00006: Selective Electroless Nickel Deposition on PMMA using Chloroform Pre-Treatment Nicholas Sipes In the past 5 years, we have discovered that chloroform promotes the adhesion of thin gold films to Poly(methyl methacrylate) surfaces. Based on this new understanding of the interaction of chloroform with PMMA and metal atoms, we were curious to see if chloroform would promote the adhesion of Nickel to PMMA deposited by electroless plating. My goal was to selectively electroless plate Nickel onto PMMA. Chloroform was spun-cast onto 1 inch square PMMA substrates. I used electrical tape to shield one half of the PMMA from the chloroform during spin-casting; this allowed for a direct comparison of treated vs. untreated. The samples were then put through hydrochloric acid and a series of baths provided by Transene Company Inc. to electrolessly deposit nickel on the sample. After many trials, there was a clear distinction in the adhesion strength of the Nickel to the plain PMMA surface vs. the chloroform pre-treated surface. Showing that it is possible to create chloroform sites via spin-casting for electroless nickel plating on PMMA opens up the challenge to better understand the chemistry taking place and to perfect the electroless plating process. [Preview Abstract] |
Friday, November 11, 2016 11:57AM - 12:09PM |
G2.00007: Laser Shock Wave Assisted Patterning on NiTi Shape Memory Alloy Surfaces Byron Grant, Dovletgeldi Seyitliyev, Khomidkhodza Kholikov, Haluk Karaca, Peizhen Li, Ali ER Shape memory alloys are a unique class of smart materials that have become of recent interest in engineering, biomedical and aerospace technologies. We report an advanced direct imprinting method with low cost, quick, and low environmental impact to create thermally controllable surface pattern using laser pulses. Patterned micro indents were generated on NiTi SMAs using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities generating pressure pulses up to 10 GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the NiTi surface. AFM, SEM and optical microscope images of square pattern with different sizes were obtained. One dimensional profile analysis show that depth of the pattern initially increased linearly until the optical breakdown of the transparent overlay occurs and dense ionized plasma absorbs and reflects the laser beam. Experimental data is in good agreement with theoretical simulation of laser induced shock wave propagation inside material. Rapid attenuation and dispersion of stress wave was observed. [Preview Abstract] |
Friday, November 11, 2016 12:09PM - 12:21PM |
G2.00008: Surface characterization of pipeline surface using replica techniques Hamza Shams, Kanza Rahman, Mohsin Aziz Raja, Raja Hamza Sajid, Muhammad Fahad Khan Pipes are widely used in the petroleum industry for distribution of refined oil. During their service life they lose their surface characteristics. Replica techniques provide a non-destructive way to analyze on-field pipelines for surface cracks and impregnation due to corrosion. The use of replica techniques provide an effective way to predict failure characteristics of these pipes. This study aims to compare the different replica techniques used in such investigations. Atomic force microscopy (AFM) coupled with standard optical microscopy has been used to evaluate surface topography of the actual and the replica surface. The surface micrograph obtained from the replica is then inverted and analyzed for variations through software analysis. The variations are representative of the resolution of the replica technique and has been used to compare multiple replica techniques in standardized scenarios to quantify their effectiveness in on-field applications. The metallographic analysis through optical microscopy has been used to validate the methodology to develop a replica surface. The investigation summates on providing a comparative conclusion for the choice of replica techniques based on varied standardized on-field scenarios. [Preview Abstract] |
Friday, November 11, 2016 12:21PM - 12:33PM |
G2.00009: Studying Crystalline Morphology and Texture of Small Molecule Organic Semiconductor Thin Films Using Polarized Optical Microscopy, Grazing-Incidence X-Ray Diffraction and Fluid Dynamics Nan Yang, Gaurav Giri Organic semiconductors (OSCs) promise the advent of multifunctional electronics through the use of low temperature, solution processing methods of fabricating transistors on diverse substrates. OSCs are limited by low charge carrier mobilities and non-uniformity of performance. 2,7-dioctyl[1]benzohieno[3,2-b][1]benzothiophene (C8-BTBT) is a small molecule organic semiconductor that has recently reported to have charge transfer mobilities as high as 43 cm$^{2}$ V$^{-1}$ s$^{-1}$. This OSC can also form uniform thin films transistors (TFTs) by proper control of the crystalline texture and morphology. We form highly crystalline, aligned C8-BTBT thin films using a flow coating process termed solution shearing. Studying the crystal morphology and texture and structure of the resulting thin films, we show that the solution shearing process causes the thin film formation to occur where the blade movement and the evaporation of the solvent occur in similar time scales. Solution shearing C8-BTBT thin films not only demonstrates that fluid dynamics play an important role in the thin film morphology control, but also provides an insight for controlling polymorphism and TFT electrical performance, enabling us to achieving the ultimate goal of a large-area, roll-to-roll coating process. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700