Bulletin of the American Physical Society
2016 Annual Spring Meeting of the APS Ohio-Region Section
Volume 61, Number 5
Friday–Saturday, April 8–9, 2016; Dayton, Ohio
Session D1: Contributed Session I: Materials Research |
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Chair: Andrew Evwaraye, University of Dayton Room: SC146 |
Saturday, April 9, 2016 8:30AM - 8:42AM |
D1.00001: Study of shallow traps in SrTiO3 using thermo-luminescence spectroscopy pooneh saadatkia, Farida Selim Strontium titanate (SrTiO$_{\mathrm{3}})$ is an important complex oxide with an unusual dependence of dielectric function on temperature and electric field. This special property makes it as an interesting material for fundamental and applied research. In order to investigate the presence of shallow traps in bulk single crystals of SrTiO3, Low temperature thermo-luminescence (TL) spectroscopy was applied before and after laser excitation. A TL peak close to the phase transition temperature and an unusual behavior for the kinetics of TL process in STO crystals have been observed. The TL peak was disappeared after annealing the sample in air. Measurements revealed that 266 nm femtosecond laser pulses induce permanent shallow traps in STO crystals. The formation of such stable traps may be due to lattice relaxation which seems to be behind many interesting phenomena in STO. [Preview Abstract] |
Saturday, April 9, 2016 8:42AM - 8:54AM |
D1.00002: Hysteresis loops on transition metal doped Zinc Oxide thin film using Sol-Gel method Sunil Thapa, Pooneh Saadatkia, Farida Selim Transition metal doped also known as Diluted magnetic semiconductors (DMS) are in rise due to their potential application in Spintronic devices. Sol-gel method was used to deposit transition metal doped zinc oxide in a glass substrate and dry at 120 \textdegree C for 10 minutes. After coating 16 times, the films were annealed depending upon the dopant materials. This method is a cheap way to obtain uniform thin films. SQUID (Superconducting Quantum Interference Device) was done to measure the extremely subtle magnetic field. Most of the doped zinc oxides showed hysteresis loop, but for 2{\%}Al3{\%}Co doped zinc oxide observed inverted hysteresis loops. The reversed hysteresis can be explained using a two layer model. In addition, SEM (Scanning Electron Microscopy) was done to observe the surface structure and spectrometer was used to measure the absorbance of the thin film. [Preview Abstract] |
Saturday, April 9, 2016 8:54AM - 9:06AM |
D1.00003: Structural and Optical Properties of UV Irradiation -- Assisted Annealed Al:ZnO Thin Films Anthony Colosimo, David Winarski, Sunil Thapa, Farida Selim Transparent Al:ZnO thin films, prepared by the sol -- gel method and deposited on quartz substrates, underwent an irradiation -- assisted annealing process involving irradiation at different wavelengths within the near UV range from laser and LED sources. Irradiation -- assisted processes are often used in materials synthesis and characterization for various purposes, and the effect of the near UV irradiation during low annealing temperatures on the formation and conductivity Al:ZnO thin films isthe primaryfocus of this study. The UV irradiation was implemented over a range of annealing temperatures from 100$^{\mathrm{o}}$Cto 300$^{\mathrm{o}}$C, and these films were then studied by X -- ray diffraction, scanning electron microscopy, photoluminescence measurements and other spectral analysis. [Preview Abstract] |
Saturday, April 9, 2016 9:06AM - 9:18AM |
D1.00004: Optical Absorption and Luminescence Studies of Sn Doped ZnO Single Crystals Micah Haseman, Matthew Kusz, Keith McBride, Pooneh Saadatkia, Farida Selim High quality undoped and Tin doped Zinc Oxide (ZnO:Sn) single crystals were grown by the chemical vapor transport (CVT) method and studied by optical absorption and thermo-luminescence (TL) spectroscopies. Significant changes in TL and absorption spectra were induced by Sn doping. By varying Sn concentration, the color of the samples has changed from colorless to dark blue. Optical absorption measurements revealed no change in the band gap and indicated that the dark blue color is due to a broad peak beyond 600 nm. Following our recent approach in applying low temperature TL in measuring donor ionization energies in ZnO, inspection of TL glow spectroscopy showed a change in the donor ionization energy and density after doping. [Preview Abstract] |
Saturday, April 9, 2016 9:18AM - 9:30AM |
D1.00005: Identification of chemical environment of defects in ZnO by means of digital coincidence Doppler broadening of positron annihilation spectroscopy. Petr Stepanov The first fully digital Doppler broadening positron annihilation spectrometer has been developed and employed to investigate point defects in ZnO single crystals. ZnO crystals were grown by chemical vapor transport method and annealed in hydrogen and deuterium atmospheres. Doppler broadening measurements were carried out in single-detector, coincidence and timestamp acquisition modes. Digital signal processing dramatically improves quality of data and the energy resolution, increasing the sensitivity of the spectrometer. This enables precise measurements of the electron momentum of core electrons which retain the chemical identity and thus reveals the chemical environments of impurities and clusters around defects even for very small concentrations. The electron momentum distributions of as-grown, hydrogen-doped, and deuterium doped ZnO single crystals were measured and expressed as ratio curves of the electron momentum of aluminum. Presence of H and D atoms in ZnO is reflected by a notable change in the obtained ratio curves. The developed system allows detection of very small concentration of clusters, which is significantly important for existing and future ZnO applications in optoelectronic and spintronic devices. [Preview Abstract] |
Saturday, April 9, 2016 9:30AM - 9:42AM |
D1.00006: Characterization of neutron-induced defects in metals by positron annihilation spectroscopy Tara Gray, Petr Stepanov, Donald Wall, Farida Selim The development of radiation-tolerant materials is crucial for the next generation of nuclear fission and fusion reactors. Recent molecular-dynamic simulations predict that nanostructured materials may demonstrate radiation resistance due to effective defect annealing at the grain boundaries. In this work, we investigate and compare neutron-induced defects in copper in the single crystal and ceramic forms. Samples were irradiated by neutrons inside a nuclear reactor and characterized by positron lifetime spectroscopy and Doppler broadening measurements. The study reveals the effect of grain boundaries on defect formation and annealing. [Preview Abstract] |
Saturday, April 9, 2016 9:42AM - 9:54AM |
D1.00007: Study of the Source Contribution to the Positron Lifetime Spectrum. Md Salah Uddin, Herbert Jaeger We are investigating the source contribution of a $^{\mathrm{22}}$Na positron source to the positron annihilation lifetime spectrum. We use a standard a fast-slow delayed coincidence apparatus to record positron lifetimes in simple metal samples. Our samples are commercial grade, and an annealing process is developed to minimize the defect concentration in the samples. The goal of the process is to allow separation of bulk lifetimes from the components due to source contributions. Multiple measurements will be performed to quantify the contribution of the positron source to the lifetime spectrum. 0 [Preview Abstract] |
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