Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session H06: Instrumentation and Measurements I |
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Sponsoring Units: GIMS Room: LACC 153A |
Tuesday, March 6, 2018 2:30PM - 2:42PM |
H06.00001: Unveiling a laser-free 300 kV stroboscopic TEM with a projected sub 10-ps temporal resolution June Lau, Karl Schliep, Michael Katz, Jason Gorman, Yimei Zhu, Chunguang Jing, Alexei Kanareykin, Ao Liu, Yubin Zhao, Bryan Reed, Daniel Masiel For the last several decades, time-resolved transmission electron microscopes (TEM) exploring the sub-microsecond timescale have relied on laser-actuated photocathodes for precisely timed, pulsed probe beams, while another laser beam, typically locked to or split-off from the probe-generating laser, delivers the sample stimulus (pump). These instruments can study a wide range of laser-driven phenomena in both stroboscopic and single-shot modes, for repeatable and one-time events, respectively. However, not all processes of interest are amenable to the laser-driven approach. In the last three years, this collaboration has made substantial progress towards pioneering a new kind of time-resolved TEM, complementary to the existing laser-based techniques. Using RF beam-modulators, we can achieve a pulsed electron beam at 10% duty cycle with continuously tuneable GHz and MHz pulse rates. This RF-modulator approach extends the application of time-resolved TEM to in operando, electromagnetically-pumped experiments up to 20 GHz. |
Tuesday, March 6, 2018 2:42PM - 2:54PM |
H06.00002: Atomic Electron Tomography: Probing 3D Structure and Physical Properties at the Single-Atom Level Yongsoo Yang, Rui Xu, Alan Pryor Jr., Li Wu, Jihan Zhou, Matthias Bartels, Michael Sawaya, Jianwei Miao, Chien-Chun Chen, M. C. Scott, Peter Ercius, Colin Ophus, Fan Sun, Hao Zeng, W. Theis, Markus Eisenbach, Paul Kent, Renat Sabirianov, Hendrik Heinz, Hadi Ramezani-Dakhel, Laurence Marks To understand material properties and functionality at the fundamental level, it is essential to precisely determine their 3D atomic arrangement. For crystalline materials, crystallography can provide this information. However, perfect crystals are rare in nature. Real materials often contain crystal defects, surface reconstructions, nanoscale heterogeneities, and disorders, which strongly influence material properties and performance. Here, we present atomic electron tomography (AET) for 3D structure determination of crystal defects and disordered materials at the single-atom level. By combining the tomographic tilt series acquired from aberration corrected electron microscopes with advanced algorithms [1], we localized the coordinates of individual atoms and point defects in materials with a 3D precision of ~19 pm, and determined full 3D strain tensor [2]. More recently, we determined the 3D coordinates of 6,569 Fe and 16,627 Pt atoms in an FePt nanoparticle, and correlated chemical order/disorder and crystal defects with material properties at the individual atomic level [3]. |
Tuesday, March 6, 2018 2:54PM - 3:06PM |
H06.00003: X-ray Diffraction in the 25 T Florida Split Coil Magnet at the National High Magnetic Field Laboratory (NHMFL) Drew Rebar, Kaya Wei, Josiah Cochran, Julia Smith, Alexey Kovalev, Alexey Suslov, Theo Siegrist A novel x-ray diffraction system is under construction at the 25T Florida split coil magnet at the DC Field Facility of NHMFL, Tallahassee, FL. The purpose of the system is to probe spin-lattice coupling and crystal structure transitions as observed in various metamagnetic, magnetocaloric, multiferroic, and magnetostrictive materials. The project builds upon the proof-of-concept study at NHMFL by Wang, et al (Rev Sci Instrum 86, 123902, 2015) and fills a niche among applied field diffraction systems for the following reasons. First, high-field diffraction is made possible with small sample sizes compared to the large sample sizes needed for neutron diffraction. Second, high-field diffraction is made possible for materials with inherent difficulties in pulse fields (sample heating, etc). In addition to the 25T split coil magnet, the primary elements of the system consist of a Mo rotating anode x-ray source and a PILATUS 300K-W X hybrid pixel array detector customized to tolerate the fringe field of the split coil magnet. The challenges of XRD in a magnetic field, the strategies to overcome them, and the ongoing evolution of the system are discussed. A preliminary study of metamagnetic materials is presented with emphasis on the role of high-field XRD in the investigation. |
Tuesday, March 6, 2018 3:06PM - 3:18PM |
H06.00004: Utilizing photoactivated ZnO-coated silica nanospring mats for chemical detection Lyndon Bastatas, Elena Echeverria, Punya Mainali, Phadindra Wagle, Aaron Austin, Dave McIlroy Detecting ammonium nitrate remains difficult owing to its low vapor pressure. To address this, we are investigating the utility of silica-based nanospring mats coated with zinc oxide as the sensors. We are measuring the electrical responses of the sensors when exposed to heated ammonium nitrate while illuminated with near-UV light source in ambient condition. In general, since the ZnO coated nanosprings have very high surface-to-volume ratio, they offer a wider area for components of ammonium nitrate to interact with oxygen ions in the sensors, thereby making them more sensitive compared to thin films. In addition, illuminating the sensors help in generating electron-hole pairs that would offset the effect of redox processes in their detection capabilities. The generated holes can recombine with the adsorbed O2 species in the surface and the uncompensated electrons enhance the electrical conductivity. Furthermore, to improve the sensors’ selectivity, we are exploring the usage of functional groups that can attract ammonium nitrate. |
Tuesday, March 6, 2018 3:18PM - 3:30PM |
H06.00005: Casimir-driven Parametric Amplification of a MEMS Accelerometer Alex Stange, David Bishop In this work, we use the gradient of the attractive Casimir interaction existing between an Au-coated silicon plate and an Au-coated microsphere bonded to the proof mass of a commercial MEMS capacitive accelerometer to modulate the effective spring constant of the MEMS proof mass. By modulating this system parameter, the accelerometer output at resonance can be greatly amplified or de-amplified depending on the frequency and phase of modulation. The extraordinary distance dependence of the Casimir force (1/r3 for a sphere-plane geometry) leveraged with the parametric amplification results in a system capable of resolving sub pm changes in sphere-plate separation or sub pN changes in force. On top of that, the robust built-in signal processing in the MEMS circuitry provides low noise density of ~fN/√Hz. Such a highly sensitive device allows for further investigation into the not yet fully understood physics of Casimir cavities and also provides a versatile platform for conducting a variety of quantum metrology experiments. |
Tuesday, March 6, 2018 3:30PM - 3:42PM |
H06.00006: Efficiency of Nanoelectrothermal Actuators in Fluids Atakan ARI, Mehmet Hanay, Kamil Ekinci Electrothermal actuation relies on non-uniform thermal expansion of a bilayer structure that consist of materials with different thermal expansion coefficients. Typically, a small metallic electrode on a suspended semiconductor structure is heated by a periodic voltage, which excites mechanical oscillations of the structure. Electrothermal actuators have recently been scaled into the NEMS domain, thanks to advances in nanofabrication methods. To date, most electrothermally-actuated devices have been operated in vacuum; however, future NEMS applications are in fluids. Here, we characterized the efficiency of nanoelectrothermal actuation in different fluids, such as air and water. We fabricated doubly-clamped silicon nitride nanomechanical beam resonators with gold actuation and detection loops. We then measured the displacement amplitudes of the beams as a function of the excitation power using optical interferometry. With data from devices and actuators of different linear dimensions, we developed a model for nanoelectrothermal actuation in fluids. |
Tuesday, March 6, 2018 3:42PM - 3:54PM |
H06.00007: Applying four coefficient transport measurements to strongly correlated electron systems Keith White, Joseph Roth, Alexej Pogrebnyakov, Lei Zhang, Roman Engel-Herbert The direct experimental determination of transport relevant parameters, such as effective mass and scattering time, is conventionally achieved using Shubnikov de Haas oscillations, which occur in the limit of high magnetic fields. In strongly correlated electron systems the conduction band width is usually narrow and the strong electron-electron interaction results in a mass enhancement, making it difficult to fulfill this criteria. An elegant way out of the dilemma is the determination of the four transport coefficients resistivity (ρ), Seebeck (α), Nernst (Q), and Hall (RH) to determine transport relevant parameters1. We report on an experimental setup to determine these four transport coefficients, which has been integrated into a PPMS system. The validity of the measurements is shown by analyzing Al-doped ZnO and Sn-doped In2O31, and then utilized to determine effective carrier mass and scattering time from the strongly correlated metal SrVO3 as a function of temperature. |
Tuesday, March 6, 2018 3:54PM - 4:06PM |
H06.00008: Measuring Hall Conductivity Using a Cantilever Torque Magnetometer Samuel Mumford, Aharon Kapitulnik, Tiffany Paul, Amir Yacoby We present measurements of Hall conductivity of a Corbino-disc patterned thin film sample fabricated on a cantilever-based torque magnetometer. Applying a voltage difference across the disc creates a magnetic dipole moment propotional to σxy. This dipole moment interacts with an applied magnetic field, exerting a torque on the cantilever. Such a technique uses symmetry to eliminate the longitudinal resistance dependence which spoils measurements of σxy in insulators at low temperaure. We have fabricated high-Q cantilevers with Corbino-disks and tested the minimum detectible σxy both at room temperature and when cooling. Our preliminary results indicate that this technique could be used to accurately probe σxy in previously inaccessible materials. |
Tuesday, March 6, 2018 4:06PM - 4:18PM |
H06.00009: Fast Hall™: A High Speed Hall Measurement for Material Characterization Jeffrey Lindemuth The Hall effect is the primary method to measure carrier density, mobility and carrier type in materials. The most common method for measuring the Hall effect in semiconductors uses a DC magnetic field. This method depends are reversing the direction of the magnetic field. This method breaks down for materials with mobility < ~ 10 cm2 /(V s). We present a measurement protocol based on the reverse-field reciprocity theorem. The reverse-field reciprocity theorem considers a four-port network with current inputs and voltage measurements and an applied magnetic field. If a current is applied to two of the inputs (say 1 and 3) and a positive field B a voltage (V) is measured on terminals 2 and 4. If the current and voltage leads are interchanged, current on terminals 2 and 4, voltage measured between 1 and 3, V2(B). The theorem states that V2(B) = V1(-B). This is a very general result; the only requirement of the material is that it is electrically linear. This means that thermoelectric voltages require special treatment. The method presented here has been extended for material characterization, in particular the measurement of low mobility materials based of the reverse-field reciprocity theorem. |
Tuesday, March 6, 2018 4:18PM - 4:30PM |
H06.00010: Characterization of XFEL single pulses using single particle imaging: application to PAL-XFEL Heemin Lee, Do Hyung Cho, Daewoong Nam, Sangsoo Kim, Tae-Yeong Koo, Do Young Noh, Changyong Song XFELs from the SASE lasing process produces single pulses with intrinsic stochastic nature. Thus, understanding the characteristics of each individual X-ray pulse is important for applications exploiting single femtosecond X-ray pulses. Here we introdue that single particle diffraction imaging can provide a straightforward route to characterize the X-ray pulse energy and spatial coherence of each single pulse radiation from XFELs. This straightforward experimental scheme reduces the effort in developing much demanding appratus for an absolute flux measurements, etc. Analysis was made for the data obtained from recently established PAL-XFEL. |
Tuesday, March 6, 2018 4:30PM - 4:42PM |
H06.00011: Dynamic Characterization of Nanomaterials Using Acoustic Levitator Md Abdul Momen, Ahmed Farghaly, Nicholas Debban, Kamlesh Suthar, Anthony DiChiara Acoustic levitation provides a platform to trap and hold a small amount of material by using standing pressure waves and obviates the need of a container. The technique has a potential to be used for experiments that utilize a combination of laser and x-ray beams; x-ray scattering and laser distortion from the container can be avoided, sample consumption can be minimized, and unwanted chemistry that may occur at the container interface can be avoided. In an effort to integrate acoustic levitator into small angle X-ray scattering (SAXS) experiment at Advanced Photon Source (APS), a solution of gold nanoparticles has been dispensed and trapped into acoustic levitator for the time-resolved characterization of the nanoparticles. Results showed good reproducibility and a cumulative damage mechanism, likely due to the laser removal of the ligands from the nanoparticles. In another experiment, gold nanoparticles have been synthesized in the acoustically levitated droplets. Two microdispensers were employed to inject the solutions, a gold precursor (HAuCl4) and a reducing agent (NaBH4), into the levitator for mixing and synthesis of nanoparticles. SAXS was used for real-time characterization of nanoparticles formation. |
Tuesday, March 6, 2018 4:42PM - 4:54PM |
H06.00012: Testing Interpretations of Electron-Phonon Coupling as Measured by RIXS Keith Gilmore, Andrey Geondzhian Electron-phonon coupling plays a key role in many condensed matter phenomena, notably superconductivity. However, this quantity can be difficult to measure, particularly in many unconventional superconductors for which large, single crystals cannot be grown. Even in these challenging cases resonant inelastic X-ray scattering (RIXS) is sufficiently sensitive to probe both the phonon dispersion and electron-phonon coupling strength. Correctly quantifying the latter remains contentious. We turn to simple organic molecules, such as acetone, to perform quantitative tests on the interpretation of electron-phonon coupling as probed by RIXS. We use density functional theory and excited-state calculations to obtain parameters for typical model Hamiltonians and test whether the models, with calculated, non-adjustable parameters, can explain the experimental RIXS data. We apply our improved understanding of RIXS modeling to explain recent experimental data on strontium titanate and STO/LAO multilayers. |
Tuesday, March 6, 2018 4:54PM - 5:06PM |
H06.00013: Resonant Inelastic X-ray Scattering studies of Rare Earth Hexaborides Donal Sheets, Sahan Handunkanda, Erin Curry, Vincent Flynn, Jian-Xin Zhu, Maxim Dzero, Diego Casa, Mary Upton, Jung Ho Kim, Thomas Gog, Priscilla Rosa, Zachary Fisk, Ignace Jarrige, Jason Hancock We present new hard-X-ray Resonant Inelastic X-ray Scattering (RIXS) data at the L edges of several rare-earth hexaborides. Our incident-energy-, momentum-, and polarization-dependent measurements display some features which appear to be well described using density functional theory calculations related to 5d bands in these materials. Polarization-dependent data shows anomalies particularly at high incident energy in the divalent materials and we propose a process which describes the origin of this scattering. Our investigations lay the groundwork for future high energy resolution RIXS studies in materials based on f electrons, where moment screening, hybridization, and mixed valency control the low-energy behavior. |
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