Bulletin of the American Physical Society
2019 Annual Meeting of the APS Far West Section
Volume 64, Number 17
Friday–Saturday, November 1–2, 2019; Stanford, California
Session B02: Poster Session - Condensed Matter and Material Sciences |
Hide Abstracts |
Chair: Hendrik Ohldag, Lawrence Berkeley National Laboratory Room: Huang Engineering Center Foyer |
|
B02.00001: Electrostatic Gating in Carbon Nanotube (CNT) Networks Using Scanning Gate Microscopy Savannah Silva, Marissa Dierkes, Erica Happe, Natalie Plank, Colleen Marlow Carbon Nanotube (CNT) field effect transistor aptasensors show promise for biosensing applications because of their sensitivity to electrical changes in the environment at the molecular level. Previous work using a biased atomic force microscope (AFM) tip to electrostatically gate specific locations in the network demonstrated that individual metallic-semiconducting junctions were sensing hotspots. To better understand the role of these junctions within the context of the entire network morphology, we created a scanning gate microscopy setup using a conductive AFM tip as a movable, localized gate and an electronic measurement system to track the network current. The change in device current is measured using a multichannel lock-in amplifier as the conductive tip of fixed bias and height is scanned over the network. The resulting data reflects the response of the network to specific network locations being gated. We combine the conductance data with the topographic AFM image to create a conductive map which can reveal regions of higher network sensitivity. We have successfully created a scanning gate microscopy system at Cal Poly making it possible to map the electrical sensitivity across the entire CNT network to localized gating. [Preview Abstract] |
|
B02.00002: Estimating Schottky barrier heights using the current characteristics of sparse CNT networks Alejandro Jimenez, Hong Phan Nguyen, Natalie Plank, Colleen A. Marlow Carbon nanotube (CNT) thin film networks are a promising platform used for field effect transistor devices with bio-sensitivity. There is compelling evidence that this sensitivity occurs due to changes in the transport across metallic (m) and semiconducting (s) tube junctions in the network due to electrostatic gating. Transport across individual m-s junctions is asymmetric and nonlinear due to the Schottky barriers formed at the m-s CNT junctions. In large dense CNT network devices the nonlinear signature of individual m-s junctions is washed out in the overall current characteristics. However, we have observed the nonlinear signature of the m-s junctions in the current characteristics of sparse CNT network devices. To understand the interaction between the individual junctions and the overall network morphology we studied the current characteristics of sparse CNT network devices from room temperature down to 20 K. By varying the temperature of these devices we were able to probe the energetic dependence of the CNT Schottky barriers. We used two distinct models to extract the height of the Schottky barriers from the set of temperature data. While the models differ significantly, both models suggest a transition in the dominant transport mechanism at low temperatures. [Preview Abstract] |
|
B02.00003: Reversible Motion of a Contact Line Charity Lizardo, Esmeralda Orozco, Audrey Profeta, Nathan Keim We study behavior of the liquid-solid-vapor contact line between two solid plates. A syringe pump injects water though one plate which is kept in a narrow gap between the plates, forming the contact line. The pump cyclically injects and withdraws a small, constant volume of water, changing the contact line shape. After each cycle, we take photos of the contact line from above. When we compare subsequent photos, we find that after many cycles the contact line reaches one of two steady states: a reversible steady state, where its shape stops changing, or a fluctuating steady state, where its shape continues to change slightly. Experiments on glass plates show a reversible steady state even at high volumes. However, experiments on acrylic show a fluctuating steady state at high volumes. We investigate the critical volume that marks the transition between low-volume reversible steady states and high-volume fluctuating steady states on acrylic. [Preview Abstract] |
|
B02.00004: Memory in a Contact Line Esmeralda Orozco, Charity Lizardo, Audrey Profeta, Nathan Keim We investigate whether cyclically driving a liquid-solid-vapor contact line can encode memory. We use a syringe pump to infuse and withdraw a set volume of water in a narrow gap between the two glass plates. This allows for the shape of the contact line to change each time the system is driven. To analyze the evolution of the contact line, we take photos after each cycle. Comparing each subsequent image to each other, we find that the contact line may become reversible, so that its shape stops changing. This behavior is seen even at high volumes. This motivated the search for memory behavior in the contact line. We train the contact line with a certain volume to reach a steady state. This establishes a memory of the training volume that allows the steady state to be recovered by applying the training volume at a later time. This memory is erased by applying larger volumes, but not smaller volumes. These behaviors are reminiscent of return-point memory, best known in ferromagnets. Our results indicate memory exists, and that the trained volume can be stored as retrievable information in the contact line. [Preview Abstract] |
|
B02.00005: Electrical Current Characteristics of Simulated Carbon Nanotube Network Field Effect Transistors James Raj, Roberto Valenzuela, Colleen Marlow \begin{figure}[htbp] \centerline{\includegraphics[width=0.32in,height=0.33in]{270920191.eps}} \label{fig1} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.25in,height=0.25in]{270920192.eps}} \label{fig2} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.32in,height=0.33in]{270920193.eps}} \label{fig3} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.25in,height=0.25in]{270920194.eps}} \label{fig4} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.32in,height=0.33in]{270920195.eps}} \label{fig5} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.25in,height=0.25in]{270920196.eps}} \label{fig6} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.32in,height=0.33in]{270920197.eps}} \label{fig7} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.25in,height=0.25in]{270920198.eps}} \label{fig8} \end{figure} Carbon nanotube (CNT) network field effect transistors (FETs) offer a promising method for creating biosensors. Sensing occurs due to electrostatic gating which impacts the metallic-semiconducting (m-s) junctions in particular, and is heavily influenced by the morphology of the CNT network. Using a simulated random stick network, we assigned sticks to be either metallic (m) or semiconducting (s) with ratios and densities similar to actual devices and simulated electrostatic gating at each m-s junction in the network. For biosensing applications CNT FETs should have optimized sensitivity. However, it is not fully understood how a network's morphological parameters impact its overall network sensitivity. Using our simulation, we mapped sensitivity as the impact of gating each m-s junction within the network to the overall change in network current. This process was done for multiple simulated networks of varying tube densities. Our results showed that not all m-s junctions influence the network the same, and allowed us to determine which m-s junctions act. In addition, we verified that m-s junctions most influence the network response when the networks are of low density affirming that sparse networks have higher sensitivity. [Preview Abstract] |
|
B02.00006: Computationally Analyzing the Impact of Schottky Barriers on Current Characteristics of Carbon Nanotube Networks Samuel Philliber, Roberto Abril Valenzuela, Alejandro Jimenez, H.P. Nguyen, N. O. V. Plank, C. A. Marlow Nonlinear asymmetric current characteristics have been observed in field effect transistor device in which sparse networks of carbon nanotubes (CNTs) are the active layer. We propose this asymmetry is due to Schottky barriers formed at the junctions between metal (M) and semiconducting (S) carbon nanotubes within the network. To determine if this is the case we simulated random stick networks of low density and assigned sticks as either metal or semiconducting with the same ratio as the actual device networks. We then modeled the M-S junctions in the simulated network as ideal diodes. Using modified nodal analysis, we are able to simulate a potential difference across our simulated networks and determine the current. In this way we generated current voltage characteristics for multiple simulated networks of density and metallic ratio of the measure device. We observe current characteristics similar to what is seen experimentally indicating that the Schottky barriers at M-S junctions within CNT sparse networks have significant impact on the overall network properties. [Preview Abstract] |
|
B02.00007: First principles study of electronic, magnetic and inter-layer coupling in a layered magnetic insulator Santosh KC, Michael McGuire, Valentino Cooper The crystallographic, electronic and magnetic properties of layered CrCl$_{3}$ were investigated using density functional theory. We use the newly developed spin van der Waals density functional (svdW-DF) in order to explore the atomic, electronic and magnetic structure. Our results indicate that treatment of the long-range interlayer forces with the svdW-DF improves the accuracy of crystal structure predictions. The cleavage energy was estimated to be 0.29 J/m$^{2}$ suggesting that CrCl$_{3}$ should be cleavable using standard mechanical exfoliation techniques. The inclusion of spin in the non-local vdW-DF allows us to directly probe the coupling between the magnetic structure and lattice degrees of freedom. An understanding of the link between electronic, magnetic and structural properties can be useful for novel device applications such as magnetoelectric devices, spin transistors, and 2D magnet. [Preview Abstract] |
|
B02.00008: Development of a Thin-Film Rheometer Claire Olney, Nathan Keim, Jameson Jewell, Mara Niesyt, Dani Medina, Xiang Cheng We report progress in developing a thin-film rheometer, a device used to investigate the characteristics of a freely suspended film of liquid by shearing it. The design will allow sensitive measurements and imaging of complex fluids, such as bacterial suspensions. To gather data we suspend a magnetized needle in the film and move it with an oscillating magnetic field to shear the liquid. By measuring the phase difference between the forcing current and the motion of the needle, we can extract information about the properties of the liquid, such as the viscosity. Using this principle we show a proof-of-concept measurement of the viscosity of water. By tracking particles suspended in the fluid, we find that in our current prototype the needle does not cause a simple shear in the fluid, and we will describe the implications this has for future designs of the rheometer. [Preview Abstract] |
|
B02.00009: Advancing Carbon Fiber Based Dual Extrusion Additive Manufacturing Catherine Crichton, Andrew Brown, James Lewicki, William S. Compell Additive manufacturing (AM) is a maturing and expanding technology that is going through rapid development. Researchers working to improve AM processes must be able to quickly adapt to new challenges and technological advancements while performing accurate and reproducible experiments. The work presented here is focused on facilitating this research while improving and streamlining the functionality of direct-ink-write (DIW) carbon additive manufacturing. Spanning both hardware and software, these new mechanisms and improvements will allow for additional print axes, greater reproducibility and ease of dual nozzle extrusion, rheological data collection, and an overall simpler, easier, and faster print setup procedure. These advancements will allow for future research that would not otherwise be possible. [Preview Abstract] |
|
B02.00010: Atomistic simulation of the ultrafast melting of gold: Benchmarking to experiments Jacob Molina, Thomas White With the advent of ultrafast MeV electron diffraction, experiments are now able to probe the structure of matter on a nanometer scale. Such techniques have recently been used to observe the transition from heterogeneous to homogeneous melting in gold irradiation with an ultrafast optical laser pulse. On a picosecond timescale these systems form a complex non-equilibrium state of matter that cannot be fitted with a simple linear equilibration model. Due to the commensurate spatial and temporal scales between these experiments and classical molecular dynamics, such simulations provide an ideal test-bed where additional non-linear effects can be included. However, current simulations fail to match the experimental results due to over the simplification of the general properties and behavior of the electronic and atomic subsystems. We perform new simulations that improve on those in the literature by introducing a variable electron specific heat capacity, a more physically accurate potential, and the correct thin-film geometry. As a result of these improvements, our simulations better match experimental results and more accurately predict the transition between homogeneous and heterogeneous melting. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700