Bulletin of the American Physical Society
2018 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 63, Number 18
Friday–Saturday, October 19–20, 2018; University of Houston, Houston, Texas
Session C04: Materials Science |
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Chair: Shuo Chen, University of Houston Room: Science and Engineering Classroom (SEC) 204 |
Friday, October 19, 2018 2:25PM - 2:37PM |
C04.00001: Electrode Design from Atomistic to Mesoscale Dimensions Luis De Jesus Baez, Sarbajit Banerjee The invention of rechargeable batteries has dramatically changed our landscapes and lives, underpinning the explosive worldwide growth of consumer electronics. Unfortunately, current battery technologies suffer from a myriad of challenges. Mechanistic understanding of compositional and electronic structure heterogeneities is imperative to facilitate the design of high-performing electrodes. X-ray microscopy observations indicate the formation of lithiation gradients in a LixV2O5 nanowire that arise from electron localization coupled to local structural distortions, giving rise to small polarons. I will also discuss the first direct visualization of patterns of compositional inhomogeneities within cathode materials. Two patterns are evidenced: core—shell separation and striping modulations. 3D compositional maps have been developed and translated to stress and strain maps, providing a hitherto unprecedented visualization of stress and strain inhomogeneities. Moreover, a cluster of interlaced LixV2O5 nanoparticles is evaluated, where increased heterogeneity at the interfaces suggest the exchange of Li-ions, implying a “winner-takes-all” behavior. Finally, I will discuss prospects for “beyond-Li” batteries. |
Friday, October 19, 2018 2:37PM - 2:49PM |
C04.00002: Hybrid perovskite transistor: performance limitations and solution approach Mehedhi Hasan, Chris Manspeaker, Alex Zakhidov Perovskite has been a material of extreme interest due to its dramatic improvement in performance of photovoltaic solar cells. The electronic and transport properties of perovskites have desired properties that can be used as the channel for field effect transistors (FET). However, only few reports are available on the successful fabrication of perovskite transistor (PFET) and those had limited performance. We have identified two main performance limitations of PFET from careful review of published literature. These are poor drain current and high threshold voltage (Vth). In this report, we investigated behind the limitations. Our capacitance-voltage study on perovskite/dielectric/conductor structures with different types of dielectric materials reveal that the Vth can be significantly reduced to operate PFET by selection of a suitable dielectric. Comparative I-V study of lateral vs vertical direction perovskite films were performed in dark and light. We identified that, the lateral resistivity is substantially larger than vertical counterpart which causes the poor drain current. This difference is attributed to the higher number of grain boundaries along the lateral direction as confirmed by cross-sectional SEM analysis |
Friday, October 19, 2018 2:49PM - 3:01PM |
C04.00003: Copper-induced features in rocksalt NiO using ab initio calculations Samuel R Cantrell, Luisa M Scolfaro, Pablo D Borges, Wilhelmus J Geerts Nickel oxide (NiO) is a transparent conducting oxide which has become an active area of research due to potential to be used in the next generation of Resistive RAM (RRAM) and Solar Cell devices. Doping N i1−xO with Cux has been shown to improve transparency and conductivity. The optical bandgap was experimentally found to decrease with increasing Cu concentration (from 3.2 to 2.96 eV, for x = 0% − 10%)[1]. Density Functional Theory (DFT) together with the VASP-PAW method based ab initio calculations to study the effects of substitutional Cu dopants into rocksalt NiO. Exchange-correlation effects included in the calculations within the generalized gradient approximation (GGA). To better describe d-orbitals of Ni and Cu a Hubbard potential U contribution was added (GGA+U). Results also considering a hybrid functional (HSE06) to treat exchange correlation are shown for pristine and Cu-doped systems. Doped NiO systems were studied using supercells grown along [111] direction of 32 and 108 atoms to simulate anti-ferromagnetic configurations. Concentrations of Cu of 1.85%, 3.70%, 6.25%, and 12.5% were investigated. Cu-induced trends in the stability and energetics of NiO are analyzed as a function of doping concentration. |
Friday, October 19, 2018 3:01PM - 3:13PM |
C04.00004: Crystal grain orientation and characterization mapping in CVD diamond using polarized micro-Raman spectroscopy. Jaime Ruiz-Avila, M Nazari, Raju Ahmed, Mark W Holtz Raman spectroscopy is well-established method of characterizing samples. Polarized Raman methods have been previously shown to be effective in determining the crystal orientation of a point on a specific grain within a polycrystalline silicon sample. We combine line focus micro Raman and an addressable polarization laser light source to establish an orientation mapping capability. Our technique interrogates a region of the sample and returns grain size, frequency, crystal orientation, and geographic information allowing a 2d map of the interrogated area. Parallel processing techniques are used to perform symbolic logic computations, the necessary numerical integrations, and intensity-polarization angle curve fits as well as outlier-cosmic ray filtering for effective Raman scanning at relatively low intensities and integration times. |
Friday, October 19, 2018 3:13PM - 3:25PM |
C04.00005: Cold Plasma Effects on Optical Properties of Salmon DNA Thin-films Moses O Nnaji, Ben Jang, Heungman Park Fabrication of organic semiconductor electronics is attractive due to the prospective lower cost when compared to inorganic devices. In particular, Deoxyribonucleic acid (DNA) bio-polymers show excellent promise for use in organic electronics due to their great electron-blocking/hole-transmitting capability and abundance in animal waste products. While DNA thin-films are often created by associating DNA-sodium salt with hexadecyltrimethylammonium chloride (CTMA) surfactant to promote DNA solubility in organic solvents and spin coat higher quality films, some success in reproducing uniform, water-based DNA thin-films on silicon and glass substrates has been achieved by incorporation of methanol as well as implementation of UV-ozone cleaning. Water-based salmon DNA films are being subjected to cold plasma treatment to study its effects on the films via ellipsometry and spectrophotometry, where optical properties such as the refractive index and extinction coefficient have been characterized. Key words: DNA, spin coating, cold plasma treatment, ellipsometry, spectrophotometry |
Friday, October 19, 2018 3:25PM - 3:37PM |
C04.00006: Electrical Characterization of Nickel oxide and Nickel Iron Oxide thin films and Resistive Random Access Memory Devices Grown by Radio Frequency Sputtering. James N Talbert, Wilhelmus Johannes Geerts, Luisa Scolfaro The market for non-volatile memory is potentially about to hit a brick wall with the flash technology as it might not be scalable beyond the 14nm node. The need for other storage devices is a hot topic in said market, and one possibility is Resistive RAM (RRAM). These devices can store information through a reversible switch from high to low resistance by means of a soft break-down. In this project the use of NiO and Ni1-xFexO also known as Permalloy Oxide (Ni80Fe20O, PyO) in ReRAM devices are being investigated. Device test wafers with different oxygen concentrations, thicknesses, and electrode materials were made by RF magnetron co-sputtering on p- and n-type Si wafers. Each device wafer contains 32 dies and each die 41 devices. The automated Probe system Summit 12000 was used to measure the IV and CV curves, and the impedance spectra at room temperature. Au/NiFeO/n-Si devices show a strong rectifying effect with forward currents up to 1600 times higher than the reverse current. Devices on p-Si show larger currents than similar devices on n-Si. Results will be discussed in terms of band offsets and the electrode’s work functions of the materials involved. |
Friday, October 19, 2018 3:37PM - 3:49PM |
C04.00007: Buildup Factor and Linear Attenuation Coefficient of MCP-69 alloy Muhammad Maqbool, Mohammed S Islam, Joshua Clark MCP-69 alloy was investigated using gamma ray sources ranging from 0.662 MeV to 1.333 MeV for its possible use in radiation shielding and as wedges in radiation treatment planning. Narrow beam geometries were used to determine the linear attenuation coefficient, mass attenuation coefficients and half value layer of the alloy. Linear attenuation confident was also calculated theoretically and numerically using the ideas and concepts of Compton scattering. Broad beam geometry was used to determine the Buildup factor as a function of beam energy, attenuator thickness and geometry of experimental set up. |
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