Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session D3: Undergraduate Research - Society of Physics Students III |
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Sponsoring Units: SPS Chair: Toni Sauncy, Society of Physics Students - American Institute of Physics Room: 107 |
Monday, March 3, 2014 2:30PM - 2:42PM |
D3.00001: Characterizing the Effect of Surface Hydrophobicity on Depletion Layer Shannon Petersen, Mark Seraly, Dylan McNany, Erin Brown, Adele Poynor When water meets an extended hydrophobic surface a region of reduced density called the depletion layer forms, but this phenomenon has only been experimentally verified on surfaces with contact angles \textgreater 100$^{\circ}$. Using self-assembled monolayers of organothiols on gold we produce surfaces with contact angles between 55$^{\circ}$ and 107$^{\circ}$ and then use surface plasmon resonance spectroscopy to quantify the thickness of the depletion layer formed. These experiments allow for the understanding of how the depletion layer changes with the hydrophobicity of a surface which is one of the underlying mechanisms behind several biological systems. [Preview Abstract] |
Monday, March 3, 2014 2:42PM - 2:54PM |
D3.00002: Third Sound Generation in Superfluid $^4$He Films Adsorbed on Multiwall Carbon Nanotubes Vito Iaia, Emin Menachekanian, Gary Williams A technique is developed for generating third sound in superfluid $^4$He films coating the surface of multiwall carbon nanotubes. Third sound is a thickness and temperature wave of the helium film, and in our case we detect the temperature oscillations with a carbon resistance bolometer. The nanotubes are packed in an annular resonator that is vibrated with a mechanical shaker assembly consisting of a permanent magnet mounted on springs, and surrounded by a superconducting coil. The coil is driven with an oscillating current, vibrating the cell at that frequency. Sweeping the drive frequency over the range 100-200 Hz excites the resonant third sound mode of the cell, seen as a high-Q signal in the FFT analysis of the bolometer signal. A problem with our original cell was that the mechanical drive would also shake the dilution refrigerator cooling the cell to low temperatures, and increasing the drive would start to heat up the refrigerator and the cell, which were rigidly coupled together. A new configuration now suspends the cell as a pendulum on a string, with thermal contact made by copper wires. Piezo sensor measurements show this reduces the vibration reaching the refrigerator by two orders of magnitude, which should allow measurements at lower temperatures. [Preview Abstract] |
Monday, March 3, 2014 2:54PM - 3:06PM |
D3.00003: Effects of added dopants on various triboluminescent properties of europium dibenzoylmethide triethylammonium (EuD$_{4}$TEA) Constance Owens, Ross S. Fontenot, Kamala N. Bhat, Mohan D. Aggarwal A triboluminescent (TL) material is one that emits light upon pressure, impact, friction, or mechanical shock. TL materials are desirable for investigation because they have the potential to be used as the active element for smart impact sensors. While the material europium dibenzoylmethide triethylammonium (EuD$_{4}$TEA) produces a TL emission yield that can be observed by the naked eye, it is still not sufficiently bright for use in smart sensor devices. Previous studies have shown that additional materials can be combined with EuD$_{4}$TEA in order to improve the TL emission yield. In this paper, we discuss the effects of doping on EuD$_{4}$TEA at different concentrations with a variety of materials on the TL emission yield and decay times. The dopants that were used in this study were nicotine, dibutyl phosphate (DBP), and magnesium. We also discuss both the effects of pH on EuD$_{4}$TEA, and the doping effects on impact energy. For testing triboluminescent properties, we use a custom-built drop tower that generates triboluminescence by fracturing compounds through impact. Collected data is analyzed using specially written LabVIEW programs. [Preview Abstract] |
Monday, March 3, 2014 3:06PM - 3:18PM |
D3.00004: Two-dimensional Fourier Transform Studies of Excitons in Layered Indium Selenide N. Glikin, P. Dey, J. Paul, D. Karaiskaj, Z. Kovalyuk, Z. Kudrynskyi, A. Romero Indium selenide (InSe) is a layered semiconducting material whose electronic properties are strongly influenced by many-body interactions. Having potential applications including optoelectronic and photovoltaic uses, it is necessary to understand the nature of these interactions in order to understand the material properties of interest. Three-pulse four-wave mixing (FWM) and Two-dimensional Fourier transform (2DFT) spectroscopy are used to study the many-body interactions in $\gamma $-InSe by measuring excitonic dephasing and lifetime. Excitation-density-dependent and temperature-dependent measurements of the homogeneous linewidth indicate strong contributions of exciton-exciton scattering and exciton-phonon interactions. [Preview Abstract] |
Monday, March 3, 2014 3:18PM - 3:30PM |
D3.00005: ABSTRACT WITHDRAWN |
Monday, March 3, 2014 3:30PM - 3:42PM |
D3.00006: Photo-induced Modulation Doping in Graphene/Boron Nitride Heterostructures Salman Kahn, Jairo Velasco Jr, Long Ju, Edwin Hwang, Casey Nosiglia, Hsin Zon Tsai, Wei Yang, Takashi Taniguchi, Kenji Watanabe, Dillon Wong, Yang Wang, Juwon Lee, Yuanbo Zhang, Guangyu Zhang, Michael Crommie, Alex Zettl, Feng Wang Van der Waals heterostructures (VDH) allow a modular platform for materials engineering, where various layered materials with different electrical, optical, and mechanical properties can be stacked together to enable new physics and novel functionalities. To create various VDH, we have employed a ``stamping transfer'' [1] in which two layered materials are exfoliated on separate substrates and then stamped onto each other. Several distinct VDH structures have been realized and characterized through scanned probe and optical measurement schemes. I will discuss recent progress made on these efforts, with an emphasis on optoelectronic measurements of a Graphene/Boron Nitride VDH.\\[4pt] [1] Zomer, P. J. and Dash, S. P. and Tombros, N. and van Wees, B. J., Applied Physics Letters, 99, 232104 (2011) [Preview Abstract] |
Monday, March 3, 2014 3:42PM - 3:54PM |
D3.00007: SAM Surface Domains Of 6-Amino-1-Hexanethiol Hydrochloride And 1-Dodecanethiol Mixtures on Au(111) Investigated Via AFM and STM Spectroscopy Albert Foster, John Murphy, Indrajith Senevirathne, Reshani Senevirathne Bioengineering that utilizes Self Assembled Monolayers (SAMs) has been shown to have large potential in biosensing applications. Since these SAMs can be tailored to have different functional groups attached to them, such as amine groups, it is possible to fabricate highly selective surfaces for biological species. In order to understand these surfaces better, a closer characterization of the morphology, and surface structure is needed. Differing concentrations of the solutions 6-Amino-1-hexanethiol hydrochloride (hydrophilic -- NH$_{2})$ and 1-dodecanethiol (hydrophobic -- R) were prepared, all with a total concentration of 5 mM. The mixture was dissolved in 200 proof Ethanol and hydrogen annealed Au(111) samples on mica were let self assembled in hydrocarbon free, clean glassware for a period of 24 hours to facilitate uniform and systematic assembly. These various SAM systems were then characterized via STM (Scanning Tunneling Microscopy) and AFM (Atomic Force Microscopy). The surface morphology and structure were studied via AFM tapping and phase imaging. Surface charge density variations were studied with STM. These results were then correlated against each other to understand the SAM surface system. Cumulative results of these investigations will be discussed. [Preview Abstract] |
Monday, March 3, 2014 3:54PM - 4:06PM |
D3.00008: A Study of 11-(Ferrocenyl)-1-Undecanethiol Self-Assembled Monolayers on Au(111) Surfaces John Murphy, Reshani Senevirathne, Indrajith Senevirathne SAM (Self-Assembled Monolayer) surfaces terminated with functional/charged groups have exhibited bioactive properties. Improved understanding of surface domain architecture of these systems is needed for bioengineering applications. Solutions of various concentrations of 11-Ferrocenyl-1-Undecanethiol and 1-Dodecanethiol in 200 proof ethanol in clean glassware were used to create a SAM on hydrogen flame annealed Au (111) on mica; 11-Ferrocenyl-1-Undecanethiol has been successfully used in semiconductor interfaces. The potential charge carrying effect of these thiols enables the use of STM (Scanning Tunneling Microscopy) to investigate these SAMs. These SAMs were then investigated further with an AFM (Atomic Force Microscopy) in Non-Contact mode, using topographic and phase imaging. These investigations help to characterize these SAMs from morphological, structural, and electronic perspectives. [Preview Abstract] |
Monday, March 3, 2014 4:06PM - 4:18PM |
D3.00009: Hydrophilic and Hydrophobic Probe Functionalization of 11-Mercapto-1-undecanol and 1-Dodecanthiol SAMs for Chemical Force Microscopy Mackenzie Maurer, Indrajith Senevirathne CFM (Chemical Force Microscopy), a variation in AFM (Atomic Force Microscopy) is a technique that provides details on the chemical nature of surfaces regardless of any particular morphology. An application of this surface analysis technique may lead to a deeper understanding of the surface domain architecture of SAMs (Self Assembled Monolayers) with multi component mixtures of thiols on Au(111) on mica substrates. Unique methods of probe functionalization were developed regarding the formation of SAMs of 11-mercapto-1-undecanol (hydrophilic -OH end) and 1-dodecanthiol (hydrophobic -R end) self assembled on a sputter Au coated, silicon nitride, AFM tip. Resulting hydrophilic and hydrophobic probes were evaluated with the AFM via non contact and tapping mode with topography and phase imaging to determine the success of the unique functionalization methods. Significant progress was made in developing a novel technique, which created functionalized hydrophilic and hydrophobic probes. This may lead to the identification of domains of distinct thiols on the SAMs substrates. The repeatability and accuracy of each functionalization method was assessed to determine the validity of the techniques. [Preview Abstract] |
Monday, March 3, 2014 4:18PM - 4:30PM |
D3.00010: SAM Surface Domains of (11-Mercaptooundecyl)-N,N,N-Trimethlyammonium Bromide and Dodecanthiol Mixtures on Au(111) Investigated Via AFM Michael Schell, Indrajith C. Senevirathne, John Murphy, Albert Foster III Charged/functional SAM (Self Assembled Monolayer) surfaces have many potential applications in various domains including devices for bioengineering. These surfaces also may be interesting because of the complex physics and chemistry of the charged/conductive molecular layers. The SAM used in our study is (11-Mercaptoundecyl)-N,N,N-trimethylammonium bromide, which have shown conductive properties. The substrate support for SAMs are by Au(111) on mica. Crystalline substrate Au surface was established via in-house hydrogen flame annealing. Thiolated solutions of (11-Mercaptoundecyl)-N,N,N-trimethylammonium bromide and dodecanthiol of varying concentration ratios were used as media for self assembly. Total molarity of the solutions was kept at 5mM for with the time for self assembly at 24 hours or more. Morphology, structure and conductivity characteristics were measured via tapping mode Atomic Force Microscopy (AFM) in the topography/phase imaging and Scanning Tunneling Microscopy (STM) in constant current mode. Data will be used to assess the surface structure of these systems. [Preview Abstract] |
Monday, March 3, 2014 4:30PM - 4:42PM |
D3.00011: First order reversal curve study of the dipolar interaction in Ni three-dimensional antidot arrays Bingqing Li, Xuzhao Chai, Sina Moeendarbari, Yaowu Hao, Dustin A. Gilbert, Kai Liu, Di Zhang, Gang Feng, Ping Han, X. M. Cheng Three-dimensional antidot arrays (3DAAs) have attracted considerable attention due to potential applications in sensors, energy storage and transducers. Magnetic 3DAAs also provide an ideal system for studying the effect of dimensionality and morphology on magnetic properties. We report study of dipolar interactions in Ni 3DAAs using the first-order reversal curve (FORC) method. Ordered Ni 3DAAs were fabricated by electrochemical deposition into colloidal crystal templates of self-assembled polystyrene spheres. The samples have the same pore size of about 500 nm but different thicknesses, ranging from 0.3 $\mu $m to 1.2 $\mu $m, confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). FORCs of the samples with thicknesses of 0.3 $\mu $m, 0.8 $\mu $m, and 1.2 $\mu $m were measured by a vibrating sample magnetometer. The FORC diagram analysis reveals a demagnetizing magnetic dipolar interaction, and a decrease in the interaction strength with the increasing sample thickness, evidenced by a decrease in the spread of the irreversible peak in the bias distribution, as well as a decrease in the tilting of the FORC distribution from the local coercivity axis. [Preview Abstract] |
Monday, March 3, 2014 4:42PM - 4:54PM |
D3.00012: Quartz microbalance study of photovoltaic energy balance in fullerene systems Benjamin Keller, Zijian Liu, Jacqueline Krim Energy transfer at an interface is closely linked to the topic of photovoltaic energy conversion, as well as geometries involving tip-substrate contact. To explore this phenomenon, we have employed a Quartz Crystal Microbalance (QCM) in combination with an STM for characterization of QCM oscillator amplitudes and surface morphology. With this setup we are able to detect the degree to which a temperature disparity is present between the tip (nominally at room temperature) and the sample, whose temperature can be regulated. The method provides \textit{in situ} data, making use of the fact that QCM is extremely sensitive to abrupt changes in temperature, with literature reports of sensitivities of mK or less. Similar measurements have been performed by reflecting laser light off of QCM electrodes with a variety of coatings, to explore whether the small heating effects are also detectable and can distinguish the heat absorption of the coating. Studies have been performed on fullerenes and control sample photovoltaics, to explore the balance of the incoming light energy with overall device efficiency. [Preview Abstract] |
Monday, March 3, 2014 4:54PM - 5:06PM |
D3.00013: Engineering and Characterization of Collagen Networks Using Wet Atomic Force Microscopy and Environmental Scanning Electron Microscopy Jenna Osborn, Tonya Coffey, Brad Conrad, Jennifer Burris, Brooke Hester Collagen is an abundant protein and its monomers covalently crosslink to form fibrils which form fibers which contribute to forming macrostructures like tendon or bone. While the contribution is well understood at the macroscopic level, it is not well known at the fibril level. We wish to study the mechanical properties of collagen for networks of collagen fibers that vary in size and density. We present here a method to synthesize collagen networks from monomers and that allows us to vary the density of the networks. By using biotynilated collagen and a surface that is functionalized with avidin, we generate two-dimensional collagen networks across the surface of a silicon wafer. During network synthesis, the incubation time is varied from 30 minutes to 3 hours or temperature is varied from 25$^{\circ}$C to 45$^{\circ}$C. The two-dimensional collagen network created in the process is characterized using environmental atomic force microscopy (AFM) and scanning electron microscopy (SEM). The network density is measured by the number of strands in one frame using SPIP software. We expect that at body temperature (37$^{\circ}$C) and with longer incubation times, the network density should increase. [Preview Abstract] |
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