Bulletin of the American Physical Society
2017 Annual Spring Meeting of the APS Ohio-Region Section
Volume 62, Number 6
Friday–Saturday, May 5–6, 2017; Ypsilanti, Michigan
Session D1: Contributed: Applied Physics and Materials Science |
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Chair: Ernest Behringer, Eastern Michigan University Room: Pray-Harrold 301 |
Saturday, May 6, 2017 8:36AM - 8:48AM |
D1.00001: COMSOL modeling of filamentary switching in a RRAM device. Dipesh Niraula, Victor Karpov Resistive switching (RS) in resistive random access memory (RRAM) devices operate by the processes of growth and dissolution of the conducting filament (CF) in an insulating matrix. Several proposed microscopic models relate these processes to the migration of ions and defects. A more general phenomenological approach by our group is based on the thermodynamics of phase transformations. It involves the transitions between 3 phases representing one insulating and two conductive states of the material. That approach yields a number of analytical solutions describing RRAM operations including the current voltage (I-V) characteristics. Here, we present the corresponding numerical modeling reproducing the unique features of the I-V. Our computational technique emulates the free energy of the system and finds a stable phase configuration of the RS structure. The corresponding electric current and voltage are then computed. We use the COMSOL Multiphysics package to calculate the electric field and temperature distributions, which are used then to find the system free energy; the MATLAB package is used to find the stable phase configurations and to communicate with COMSOL. Using the known material parameters, our modeling results so far appear rather approximate compared to the measured [Preview Abstract] |
Saturday, May 6, 2017 8:48AM - 9:00AM |
D1.00002: Innovation in Earth-Abundant Hole Transport Materials for High Efficiency Cadmium Telluride Solar Cells Ebin Bastola, Kamala KhanalSubedi, Suneth Watthage, Zhaoning Song, Niraj Shrestha, Adam Phillips, Khagendra Bhandari, Michael Heben, Randy Ellingson Colloidal nanocrystal-based thin films have been demonstrated as effective light-absorbing layers for solar energy harvesting applications. Such nanocrystalline thin films can also be applied as efficient hole transport materials in solar cells including cadmium telluride (CdTe) for the efficient transfer and transport of photo-generated charge carriers. Here, we report the properties of specific earth abundant solution-processing materials acting as the efficient hole transport layers (HTLs) in CdTe solar cells, and we summarize the key properties for effective HTL's in CdTe and more generally for an arbitrary photovoltaic (PV) absorber material. Colloidal nanocrystals are promising materials for opto-electronic applications, and may in many cases be synthesized by using earth-abundant materials via a thermal-injection route. Examples of materials we will discuss include iron pyrite (FeS$_{\mathrm{2}})$, Co$_{x}$Fe$_{\mathrm{1-}}_{x}$S$_{\mathrm{2}}$, Ni$_{x}$Fe$_{\mathrm{1-}}_{x}$S$_{\mathrm{2}}$, (CuS)$_{x}$(ZnS)$_{\mathrm{1-}}_{x}$ and perovskites. The HTLs are fabricated on the top of the CdTe devices using these colloidal NCs. Our results using solution-processed NC-based thin films as HTLs for CdTe PV devices show improvements in photoconversion efficiency reaching approximately 10 {\%}. [Preview Abstract] |
Saturday, May 6, 2017 9:00AM - 9:12AM |
D1.00003: Effects of Inclusion Particle Properties on the Viscoelastic Properties of Silica/Polydimethylsiloxane Composites Nathaniel Orndorf, Richard Vallery Polymers are an important class of materials that are a part of many of our everyday products, as well as a key component in the development of new materials and technology. Polymer composites are often used in products because they offer economical and physical advantages over other materials, including the pure polymer. Although commonly used, the effects of inclusion properties (such as size, shape, material, etc.) on the composite's material properties is not fully understood. In this study, an apparatus was built in order to study the viscoelastic properties of Silica/Polydimethylsiloxane(PDMS) composites of varying filler volume fractions and particle sizes. [Preview Abstract] |
Saturday, May 6, 2017 9:12AM - 9:24AM |
D1.00004: Investigation of smart magnetic nanoparticles for the use in magnetic-field-induced hyperthermia treatment of cancer Megan Allyn, Parashu Ram Kharel, Prem Vaishnava, Ronald Tackett The use of aqueous suspensions of magnetic nanoparticles, or ferrofluids, in the magnetic-field-induced hyperthermia (MFH) treatment of cancer has emerged as a possible low-side-effect alternative to standard chemo- and radiotherapy-based treatments. Typically, superparamagnetic iron oxide nanoparticles (SPIONs) are used for their relative biocompatibility; however, their high Curie temperatures ($T_{C}$ > 500 $^{\circ}$C) require external temperature monitoring as the fluids can easily heat to temperatures well above the desired 40 $^{\circ}$C – 60 $^{\circ}$C therapeutic window. To combat this problem, we propose the use of strontium-doped lanthanum manganate nanoparticles, La$_{1-x}$Sr$_{x}$MnO$_{3}$. These materials allow for the tuning, through strontium doping, of the Curie temperature within the desired therapeutic range. The synthesis and characterization of these nanoparticles by x-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and magnetic calorimetry will be presented. [Preview Abstract] |
Saturday, May 6, 2017 9:24AM - 9:36AM |
D1.00005: Optical Method for Measuring the Curie Temperature of Magnetic Nanoparticles. Joshua Ramaglia, Corneliu Rablau, Ronald Tackett, Megan Allyn Ferrofluids - colloidal suspensions of magnetic nanoparticles in a carrier liquid -- have been investigated extensively over the past decade for their potential application in targeted cancer therapy through magnetic field induced hyperthermia (overheating) of tumor cells. The vast majority of these studies have been performed using aqueous suspensions of bio-compatible surfacted superparamagnetic iron oxide nanoparticles (SPIONs). For better temperature control, it is desirable to use ferrofluids involving ferromagnetic nanoparticles that have a Curie temperature in the 40 degrees Celsius to 60 degrees Celsius range. This allows the ferrofluid to have a built in switch that prevents it from overheating once the target temperature around 45 degrees Celsius is achieved. Such ferrofluids for self-regulated hyperthermia based on La$_{\mathrm{1-x}}$Sr$_{\mathrm{x}}$MnO$_{\mathrm{3}}$ (LSMO) nanoparticles are currently investigated in the Materials Science lab at Kettering University. In the process, there is a need for a quick -- if not most accurate -- preliminary method of determining the Curie temperature of the synthesized nanoparticles. In this work we report on the development of a visual semi-quantitative method for determining the Curie temperature based on temperature-induced changes in the light scattering patterns produced by ferrofluids in static magnetic fields. [Preview Abstract] |
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