Bulletin of the American Physical Society
2018 Annual Spring Meeting of the APS Ohio-Region Section and the AAPT Michigan Section
Volume 63, Number 7
Friday–Saturday, March 23–24, 2018; East Lansing, Michigan
Session E3: Contributed: Condensed Soft Matter, and Chemical Physics |
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Room: Biomedical and Physical Sciences Building 1300 |
Saturday, March 24, 2018 10:15AM - 10:27AM |
E3.00001: Measurements of Ultrasound Backscatter Coefficient Timothy Stiles Quantitative ultrasound imaging can produce images based on underlying physical properties of tissue. Of the various parameters that are available for imaging, the backscatter coefficient (BSC) has been of particular interest as it relates to tissue microsctructure and may indicate the presence or progression of various conditions. Despite being a basic physical parameter of tissue, measurements of BSC remain difficult in practice. Interlaboratory comparisons have yielded results that vary by up to two orders of magnitude for identical samples of tissue-mimicking materials. This investigation seeks to characterize two possible reasons for such discrepancies: nonlinear propagation and errors arising from data reduction. BSC was measured for a tissue-mimicking material consisting of glass microspheres embedded in agar gel. Data were collected over a range of peak acoustic pressures and using a variety of data reduction and analysis schemes. Results indicate that data reduction methods yield comparable results and that BSC can depend dramatically on input pressure, with difference of an order of magnitude for results collected at pressures ranging from 0.15 to 1.5 MPa in water. [Preview Abstract] |
Saturday, March 24, 2018 10:27AM - 10:39AM |
E3.00002: Single CaO accelerated densification and microstructure control of highly transparent YAG ceramic Tianyuan Zhou, Sahil Agarwal, Pooneh Saadatkia, Farida Selim, Le Zhang, Hao Chen In this work, CaO single dopant was adopted to realize the densification and microstructure control of fine- grained YAG ceramic by a solid state reaction method and highly transparent YAG ceramics were obtained after vacuum sintering at 1820 $^{\mathrm{o}}$C. The average grain size was only 2.7 $\mu $m, when the amount of CaO used was 0.045 wt.{\%}. It was found that the CaO dopant promoted densification of YAG ceramics when the sintering temperature was lower than 1660 $^{\mathrm{o}}$C, however it dramatically inhibited grain growth when the sintering temperature was further increased. [Preview Abstract] |
Saturday, March 24, 2018 10:39AM - 10:51AM |
E3.00003: Temperature dependent luminescence characteristics of Ce: YAG nanophosphors and transparent ceramics and observation of novel phenomenon Sahil Agarwal Cerium-doped YAG (Ce: YAG) has received considerable attention because of its intense emission at 525 nm and its important role in converting blue emission to white light in InGaN light-emitting diodes. In this work, the physical and luminescence properties of Ce: YAG NPs and their dependence on annealing temperature and atmosphere were investigated. Furthermore, photo-luminescence (PL) was measured as a function of temperature and compared with PL from Ce: YAG single crystals and transparent ceramics to understand the mechanism of luminescence decay with temperature. While the characteristics of PL emission as a function of temperature for single crystals and NPs are similar and follow common decay trends, Ce: YAG transparent ceramics exhibit an interesting unusual increase in PL with temperature. We explained this unique novel behavior by a 4-step mechanism involving localized states in the band gap, and provided evidence from thermo-luminescence measurements to support this interpretation. The work reveals a new luminescence phenomenon arising from the overlap of PL and TL emissions; this phenomenon is most likely characteristic of transparent ceramics. [Preview Abstract] |
Saturday, March 24, 2018 10:51AM - 11:03AM |
E3.00004: Correlation between native defects, conductivity and green luminescence in ZnO single crystals Naresh Adhikari, Petr Stepanov, Pooneh Saadatkia, Micah Haseman, Jack T. Warfield, Gerald E. Jellison, Lynn A. Boatner, Farida Selim Zinc oxide (ZnO) attracts great attention in the optoelectronic field due to its direct wide band gap and high exciton binding energy. Native point defects play a significant role on the electrical and optical properties of ZnO and should be well investigated to control the electronic properties of ZnO. In this work, bulk ZnO single crystals grown by different methods were studied using a wide range of characterization techniques including Hall Effect, Thermo-luminescence (TL) spectroscopy, Photoluminescence spectroscopy (PL), Positron Annihilation Lifetime Spectroscopy (PALS) and digital coincidence Doppler broadening positron annihilation spectroscopy. It was found that the increase in well-known green luminescence is associated with the decrease in conductivity and charge carrier concentration. Positron lifetime spectroscopy measurements were carried out to reveal the origin of defects responsible for decreasing the conductivity and enhancing the green luminescence. Thermoluminescence measurements reveal that the presence of hydrogen donors in the conductive samples. Lastly, it was interesting to observe the decrease in the ratio between green luminescence to near band emission with increasing laser power. [Preview Abstract] |
Saturday, March 24, 2018 11:03AM - 11:15AM |
E3.00005: Vertical Organic Tunnel Field-Effect Transistor Shiyi Liu, Max L. Tietze, Akram Al-Shadeedi, Vikash Kaphle, Changmin Keum, Bjorn Lussem Among the large number of different OFET designs, vertical OFETs stand out for their aggressively shortened channel length and the potential to be integrated vertically with devices such as organic OLEDs or photodiodes. However, it is challenging to control the leakage current between the drain and source by the gate electric field [Greenman, M. et al. Journal of Applied Physics, 121(20), 204503]. Here, to further optimize vertical OFET, we propose a novel OFET concept-- vertical organic tunnel field-effect transistors (VOTFETs). To realize VOTFET, drain and source contacts are heterogeneously doped in a Pentacene-based vertical OFET, which forms a p-i-n structure. Depending on the mechanism of charge carrier injection, the transistor can work in two distinct modes -- forward and backward (tunneling). The injection of charge carriers is systematically investigated, which shows that charge carriers are injected by Zener tunneling in the tunneling mode. A comparison to the lateral OFET shows that the VOTFET has an improved performance. Overall, VOTEFTs provide new ways to optimize the performance of organic transistor. Furthermore, the device principles discussed here can be applied to other material systems, broadening the impact of the results. [Preview Abstract] |
Saturday, March 24, 2018 11:15AM - 11:27AM |
E3.00006: High Transconductance Organic Electrochemical Transistor With Ionic Gel Electrolyte And Its Possible Application As Biosensor. Vikash Kaphle, Shiva Bhattrai, Shiyi Liu, Bjorn Lussem Organic Electrochemical Transistors (OECTs) are seen as a key device for the field of bioelectronics. OECTs operate in aqueous environment and at low voltages, they can be flexible, and they are bio- compatible. Currently, OECTs are mainly used as sensors, e.g. to detect ions, metabolites, hormones, DNA, Dopamine, lactic acid. Furthermore, they are used to record brain activity, the activity of electrically active cells or tissues, or to drive an active matrix display$^{\mathrm{[1][2]}}$. Transconductance is the most important parameter of OECTs as it determines the performance of the device. Here we discuss high transconductance OECTs and their limiting factors$^{\mathrm{[3]}}$. We present OECTs with a transconductance greater than 2 mS and on/off ratios in excess of 10$^{\mathrm{3}}$ using a room temperature ionic liquid (C2MIM EtSo4) and PBS as electrolyte. This electrolyte can be crosslinked into a solid gel, which is essential to integrate these devices into wearable sensors. We also discuss the origin of gate bias stress and hysteresis effects of this transistor, and propose approaches to minimize these instabilities. Furthermore, possible application of OECTs as a lactate acid sensor and neurotransmitter sensors are evaluated. References [1] X. Strakosas, M. Bongo, \textbf{2015}, \textit{41735}, 1. [2] D. Khodagholy, J. Rivnay, M. Sessolo et. al., \textit{Nat. Commun.} \textbf{2013}, \textit{4}, 2133. [3] V. Kaphle, S. Liu, A. Al-Shadeedi, C. M. Keum, B. L??ssem, \textit{Adv. Mater.} \textbf{2016}, \textit{28}, 8766. [Preview Abstract] |
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