Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B46: Undergraduate Research IIIRecordings Available Undergrad Friendly
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Sponsoring Units: APS/SPS Chair: Brad Conrad, Society of Physics Students Room: McCormick Place W-470A |
Monday, March 14, 2022 11:30AM - 11:42AM |
B46.00001: Optoadmittance Spectroscopy Steven J Marz, Kevin R Davenport, Andrey Rogachev Admittance spectroscopy detects and analyzes the magnitude and phase shift of electrical current in response to an applied oscillatory voltage. It is a well-known tool used to study dynamical and relaxational properties of electronic devices and materials. Here we present an extension of this technique into the optical domain. Similar to its electrical analog, a periodic voltage and DC bias is applied to a light emitting device. In addition to the current, the oscillatory modulation of the light is detected and its magnitude and phase shift are measured as a function of frequency. We show that this method is equivalent to the usual measurements of the relaxation in time-domain. The advantages of optoadmittance spectroscopy include a simple experimental setup and direct recording of the data in the frequency domain, which simplifies the analysis and often provides better resolution of the processes with different relaxation times. The analysis of both light and electrical current allows us to disentangle the relaxation processes related to the light emission from other purely electrical processes present in a device. This talk describes the experimental setup and presents the characterization of industry and research grade light emitting diodes and organic light emitting diodes. |
Monday, March 14, 2022 11:42AM - 11:54AM |
B46.00002: Raman Spectroscopy of Novel Materials Scott A Hillen, Christopher L Smallwood Raman spectroscopy is a powerful tool for understanding the structure of materials. In brief, the technique examines the changes in frequency that occur as a beam of light scatters off of a sample. By examining these changes in detail, one can determine properties like vibrational mode structure and symmetry classification. In this talk, we will summarize the construction and characterization of a high-sensitivity Raman spectrometer featuring an Andor Shamrock 303i spectrograph outfitted with a Zyla 4.2 sCMOS imaging array and a custom-build optical collection scheme. These developed capabilities are aimed at facilitating measurements of the quantum mechanical properties of novel materials like transition metal dichalcogenides and color centers in diamond. |
Monday, March 14, 2022 11:54AM - 12:06PM |
B46.00003: X-ray angular momentum and polarization behavior in magnetic x-ray scattering Richard E Baker, Mark P Dean, Trinanjan Datta
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Monday, March 14, 2022 12:06PM - 12:18PM |
B46.00004: Piston-cylinder clamp cell for neutron scattering experiments at high pressure, low temperature, and high magnetic field Michael E Bates, Shubham Sinha, Derrick VanGennep, Marc Janoschek, James J Hamlin Neutron scattering offers a unique method for probing the structure and magnetic properties of matter. Here, we present a pressure cell which has been designed to enable neutron scattering under conditions of high pressure, low temperature, and high magnetic field. The piston-cylinder type hydrostatic clamp cell accommodates a 120mm3 volume with sample pressures reaching as high as 3 GPa. Through careful selection of materials, the cell sustains a significant stress state while providing a wide neutron “window” to the sample without compromising on cell geometry. The process of design and development of this cell will be discussed. |
Monday, March 14, 2022 12:18PM - 12:30PM |
B46.00005: Spectral Holography: Acoustic Imaging with Broadband Sound Lauren K Jones, David G Grier
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Monday, March 14, 2022 12:30PM - 12:42PM |
B46.00006: Wide field super resolution microscopy for electronics Dongheon Ha, Emily S Wilcox, Nikolai Zhitenev As time goes on, the nanoscale components of electronic chips are getting smaller, and the smallest features are currently less than 10 nm in length. To examine the real-time operation of those chips, it is desirable to simultaneously observe the variation of physical quantities, such as electrical signal generations and transfers, in the form of optical information. In this regard, microscopy techniques that involve raster scanning, such as atomic force microscopy, are not practical for imaging despite the high spatial resolution. Therefore, the way to see real-time images of these small components would be with wide-field views on an optical microscope. However, the diffraction limit of light does not allow the optical microscope to image nanoscale features of electronic chips at a visible resolution. In this presentation, we will show how to improve the resolution of optical microscopes with arrays of high-index solid immersion lenses. Once we place a polymethylsiloxane (PDMS) mold containing those arrays of lenses atop a specimen, features smaller than the diffraction limit of optical microscopes can be clearly resolved. We will also discuss how the viscosity of PDMS affects imaging, the way to improve the positioning of lenses, and the way to convert electrical signal generations and transfer to optical information. |
Monday, March 14, 2022 12:42PM - 12:54PM |
B46.00007: Exploding single electrons in liquid helium using ultrasound focused by a Fresnel Zone Plate Ayanesh Maiti, Ambarish Ghosh, Dillip K Pradhan Electrons in liquid helium prefer to stay trapped in nanometer-sized vacuum bubbles. These bubbles can be exploded with high amplitude ultrasound and optically imaged. This serves as a means of tracking single electrons. However, material limitations make it very difficult to generate uniform pressure fluctuations of the required strength. Previous studies have attempted to resolve this issue by using hemispherical piezoelectric transducers and focusing weak sound waves into small regions. While this method allows for the imaging of electrons, observations can only be made at a single focus which is fixed by the transducer dimensions. Also, it is difficult to introduce uniform electric fields in the system due to the curvature involved. We introduce diffraction zone plates to focus plane waves in liquid helium, which allows for multiple focal spots with flexible control on positioning and amplification. We have developed a method to design zone transparency profiles from an intended focal point distribution, and fabricated a few plates using femtosecond laser micromachining technology. Remarkably, our setup has not involved curvature, enabling detailed further studies of individual electron mobilities in liquid helium. Also, our designs directly extend to studies of the long-standing problem of "exotic ions" in liquid helium. |
Monday, March 14, 2022 12:54PM - 1:06PM |
B46.00008: Temperature Dependence of the index of refraction of Rare-Earth Metal Oxides Landin M Barney The index of refraction (n) of rare-earth metal oxides provides a wide range of applications spanning from communications to photovoltaics to optics. Given the oxide’s ability to withstand extreme temperatures, this utility spans much further, especially in refractory fields which require high temperatures. This work explores the temperature dependence of varying concentrations of neodymium and yttrium thin film oxides. We perform spectroscopic scans before and after the temperature experiment at a wavelength range of 290nm-3200nm. Pre-temperature treatment measurements yield indexes of refraction of about 1.8 for all samples. Post temperature treatment, the index of refraction of all samples returns to within 10% of pre-temperature treatment values. In-situ ellipsometry is conducted at temperature values of 25°C to 600°C in an oxygen-free environment. As the temperature rises, the index of refraction tends to drop to about 80% of pre-temperature treatment values. The goal of future experiments is to determine the dependence of rare-earth metal oxides in an oxygen-rich environment, with the hopes of further expanding practical application such as being a component in high-temperature alloys. |
Monday, March 14, 2022 1:06PM - 1:18PM |
B46.00009: Design and Optimization of Epsilon-Near-Zero Metamaterial for Negative Refraction Anna Shelton, Mariama Dias Negative refraction is a nonlinear optical phenomenon in which light crosses the interface between two materials and is refracted at an angle negative relative to the normal line. Negative refraction shows great promise in applications to high depth-of-field endoscopes in oncology, as well as super lensing and ultra-fast signal processing. Negative refraction typically requires high intensity incident light to be witnessed, but through the joint phenomena of epsilon-near-zero (ENZ) modes and localized surface plasmon polaritons (LSPP), negative refraction can be achieved at orders of magnitude lower intensity incident light. In this work, we computationally optimized four materials exhibiting ENZ modes in the visible and near-infrared using a combination of three metals with strong LSPP responses and six novel nanophotonic structures in Ansys Lumerical's FDTD. We find that strongly coupled metamaterials exhibit surface energy density enhancement in excess of 300x, revealing optimal metamaterial combinations as strong candidates for producing efficient negative refraction at the on-chip scale. |
Monday, March 14, 2022 1:18PM - 1:30PM |
B46.00010: PdxAu1-x alloys for opto-electronic devices from surface plasmon resonance sensors to photocatalysts Molly K Kreider, Mariama Rebello PdxAu1-x alloys have shown promise as good candidates for applications in surface plasmon resonance (SPR) based sensors with tunable frequency and catalysis. In this work, we perform calculations using the transfer matrix method, Mie scattering, and finite-difference-time-domain analysis to evaluate the merit of various concentrations of PdxAu1-x alloys. We evaluate these alloys as SPR sensors and in photocatalysis systems in seven different media (air, water, ethanol, polyethylene, phenol, and covalent triazine). We show that Au0.65Pd0.35 exhibits particular promise for angular-based SPR sensors in covalent triazine, and Au0.86Pd0.14 exhibited the best overall merit for angular based SPR sensors with its high sensitivity and good peak definition for all sensing media. Taken together, all alloys exhibit a strong response and show promise as nanoparticle photocatalysts due to their potential for wavelength tunability. Notably, Au0.86Pd0.14 demonstrated a particularly strong integrated absorption efficiency in all environments. In an antenna-reactor heterodimer system, all alloys outperformed pure gold in integrated absorption (while maintaining comparable values to pure Pd), with Au0.86Pd0.14 outperforming all other alloyed and pure samples. |
Monday, March 14, 2022 1:30PM - 1:42PM |
B46.00011: Terahertz Broadnband Rotating Polarizer Device Chase L Lyon, Yufei Li, Daniel M Heligman, Rolando Valdes Aguilar In order to understand and depict light-matter interactions of various materials, spectroscopic responses of materials are crucial in the regime of linear-response. This allows for more in-depth analysis of quantum materials, which can differ depending on whether the incoming light is polarized with respect to the material’s symmetry axes. We report on the development of a rotating polarizer device for broadband spectroscopy in the terahertz range of the electromagnetic spectrum. This device allows for both horizontal and vertical orientations of the incoming light to be measured simultaneously. This device can generate a digital signal of about 40Hz when rotating with maximum speed. This, in turn, allows for the use of a lock-in amplifier for use in an optical set-up. |
Monday, March 14, 2022 1:42PM - 1:54PM |
B46.00012: MOKE Microscope Design and Construction Lincoln Draper, Susan Kempinger, Paul Bloom Magneto-optical Kerr effect (MOKE) microscopy is frequently employed to study the magnetic properties of a material. The microscope is generally comprised of a light source, a series of focusing optics, a polarizer/analyzer pair, a beamsplitter, an objective lens, a detector, and a magnet mounted behind the sample. There are several necessary operations to complete in order to create a functional MOKE microscope beyond simply aligning the optical components. Those operations include mounting the magnet at the proper orientation behind the sample and calibrating the magnetic field. In the case where data collection is automated, as is the case in our lab, several additional tasks must be accomplished. Those tasks primarily revolve around interfacing various pieces of equipment, such as the camera and the magnet's power supply, with the data collection program we wrote in National Instruments' LabView application. The data collection program allows the user to generate an array of magnetic field values to be applied to the sample and to take images of the sample at each field value. Once the microscope is properly setup a future area of interest includes working with various artificial magnetic systems. |
Monday, March 14, 2022 1:54PM - 2:06PM |
B46.00013: Deep learning for anomaly detection in scanning transmission electron microscopy Enea Prifti, Robert F Klie, Jack Farrell, James Buban Identifying point defects and other structural anomalies using scanning transmission electron microscopy (STEM) is important to understand a material's properties caused by the disruption of the regular pattern of a crystal. Thanks to the high spatial resolution of aberration-corrected transmission electron microscopes, atomic-resolution images with a field of view of several hundred nanometers can be taken. Such data, which often contains thousands of atomic columns need to be analyzed. This process has been done manually in the past, but recent developments in machine learning (ML) can be very useful to speed it up. In this contribution, we will utilize a convolutional variational autoencoder (VAE) which, after being trained with a set of bulk samples, generates an example (prediction) of given input images based on the trained features. We will demonstrate that the performance of a VAE in replicating an input image can be used to differentiate between bulk or defects. In the case of a bulk input, the VAE can replicate well the input within a threshold value that can be set by testing the predictions. For a defect input, the VAE will fail to output a prediction within the set threshold, allowing for a clear and automatic distinction of defects. |
Monday, March 14, 2022 2:06PM - 2:18PM |
B46.00014: Scanning Probe Microscopy of Two-dimensional (2D) Field Effect Transistors Angéline Lafleur, Ryan Plumadore, Justin Boddison-Chouinard, Laurent Molino, Adina A Luican-Mayer Transition Metal Dichalcogenides (TMDs) are 2D van der Waals materials of interest as many of them are semiconducting, opening opportunities for developing ultra-thin components such as field effect transistors. Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM) are invaluable tools for the development of such devices as they map morphology and electronic properties down to the atomic level. This enables concomitant characterization of a material’s electronic band structure, surface morphology and defects, all contributing to the behavior of the macroscopic devices. Development of TMD devices involves layer-by-layer assembly, followed by surface cleaning methods such as thermal annealing, aimed to remove residual polymers from fabrication. However, this can alter the properties of an electronic device, for example by introducing defects or electrostatic potentials. In this presentation, we aim to characterize topographic features of WSe2 devices fabricated on Si/SiO2 using a room temperature, ambient atmosphere STM/AFM and we seek to identify changes in the defect density upon heating at different temperatures. These results give insights into the microscopic behavior of electrons in 2D materials, helping to optimize the performance of 2D electronic devices. |
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