Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session S50: Focus Session: Mesoscopic Materials and Devices I |
Hide Abstracts |
Sponsoring Units: DMP Chair: John Sarrao, Los Alamos National Laboratory Room: Mile High Ballroom 1D |
Thursday, March 6, 2014 8:00AM - 8:36AM |
S50.00001: Mesoscale Science with High Energy X-ray Diffraction Microscopy at the Advanced Photon Source Invited Speaker: Robert Suter Spatially resolved diffraction of monochromatic high energy ($> 50$ keV) x-rays is used to map microstructural quantities inside of bulk polycrystalline materials. The non-destructive nature of High Energy Diffraction Microscopy (HEDM) measurements allows tracking of responses as samples undergo thermo-mechanical or other treatments. Volumes of the order of a cubic millimeter are probed with micron scale spatial resolution. Data sets allow direct comparisons to computational models of responses that frequently involve long-ranged, multi-grain interactions; such direct comparisons have only become possible with the development of HEDM and other high energy x-ray methods. Near-field measurements map the crystallographic orientation field within and between grains using a computational reconstruction method that simulates the experimental geometry and matches orientations in micron sized volume elements to experimental data containing projected grain images in large numbers of Bragg peaks. Far-field measurements yield elastic strain tensors through indexing schemes that sort observed diffraction peaks into sets associated with individual crystals and detect small radial motions in large numbers of such peaks. Combined measurements, facilitated by a new end station hutch at Advanced Photon Source beamline 1-ID, are mutually beneficial and result in accelerated data reduction. Further, absorption tomography yields density contrast that locates secondary phases, void clusters, and cracks, and tracks sample shape during deformation. A collaboration led by the Air Force Research Laboratory and including the Advanced Photon Source, Lawrence Livermore National Laboratory, Carnegie Mellon University, Petra-III, and Cornell University and CHESS is developing software and hardware for combined measurements. Examples of these capabilities include tracking of grain boundary migrations during thermal annealing, tensile deformation of zirconium, and combined measurements of nickel superalloys and a titanium alloy under tensile forces. [Preview Abstract] |
Thursday, March 6, 2014 8:36AM - 9:12AM |
S50.00002: Adding magnetic functionalities to epitaxial graphene by self assembly on or below its surface Invited Speaker: Rodolfo Miranda We show how to add magnetic functionalities to graphene's set of extraordinary electronic, mechanical or optical properties. We will discuss such two examples: \begin{enumerate} \item \textit{Achieving long range magnetic order on a monolayer of TCNQ adsorbed on graphene /Ru(0001). } \end{enumerate} Cryogenic STM and Spectroscopy and DFT simulations show that isolated TCNQ molecules deposited on gr/Ru(0001) [1-3] acquire charge from the substrate and develop a sizeable magnetic moment, which is revealed by a prominent Kondo resonance. The self-assembled molecular monolayer develops spatially extended spin-split electronic bands with only the majority band filled, thus becoming a 2D organic magnet whose predicted spin alignment in the ground state is visualized by spin-polarized STM at 4.6 K [4]. The long range magnetic order is originated by the charge transfer from graphene to TCNQ (which creates the magnetic moments) \underline {plus} the self-assembly of the molecular adlayer on the graphene layer (which creates spin-polarized intermolecular bands where the added electrons partly delocalize). Examples will be shown where the adsorbed molecules accept charge and develop magnetic moments, but do nor form bands (F4-TCNQ on graphene/Ru(0001)), or where similar bands do form, but they are not populated, because there is no charge transfer to the molecules (TCNQ on gr/Ir(111)). ii) \textit{Introducing a giant spin-orbit interaction on graphene/Ir(111) by intercalation of Pb.} The intercalation of an ordered array of Pb atoms below graphene results in the appearance a series of equally spaced, sharp peaks in the differential conductance, as revealed by STS at 4.6 K. The vicinity of Pb enhances the, usually negligible, spin-orbit interaction of graphene. The spatial variation of the spin-orbit coupling creates a gauge field that acts as an pseudo magnetic field opening a gap, confining electrons and originating pseudo Landau levels [5].\\[4pt] [1] A.L. V\'{a}zquez de Parga et al, Phys. Rev. Lett. \underline {100}, 056807 (2008);\\[0pt] [2] B. Borca et al, Phys. Rev. Lett. \underline {105}, 036804 (2010);\\[0pt] [3] D. Stradi et al, Phys. Rev. Lett. \underline {106}, 186102 (2011);\\[0pt] [4] M. Garnica et al, Nature Physics \underline {9}, 368 (2013);\\[0pt] [5] F. Calleja et al, in preparation. [Preview Abstract] |
Thursday, March 6, 2014 9:12AM - 9:24AM |
S50.00003: Parallelization of Thermochemical Nanolithography Jennifer E. Curtis, Keith Carroll, Xi Lu, Suenne Kim, Yang Gao, Hoe-Joon Kim, Suhas Somnath, Laura Polloni, Roman Sordan, WIlliam King, Elisa Riedo One of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. We demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of luminescent polymer nanostructures and graphene-based nanoribbons. [Preview Abstract] |
Thursday, March 6, 2014 9:24AM - 9:36AM |
S50.00004: Measurement of mesoscopic Si:P delta-doped devices fabricated by rapid STM hydrogen depassivation lithography via field-emission M. Rudolph, S.M. Carr, G. Subramania, G. Ten Eyck, J. Dominguez, M.P. Lilly, M.S. Carroll, E. Bussmann Recently, a method to fabricate nanoelectronic and quantum devices has been developed that utilizes scanning tunneling microscopy (STM) to place dopants (P) into Si with deterministic atomic-precision. Dopant placement is achieved via STM hydrogen depassivation lithography (HDL). Typically HDL is performed in a low-voltage tunneling mode where electrons desorb one H at a time, which requires extremely slow scan rates. Here, we introduce a high-voltage field-emission HDL, increasing patterning scan rate by an order of magnitude. Using the field-emission mode, we fabricated several HDL-patterned Si:P delta-doped devices, including a microscale multi-terminal Hall Effect device and a nanoscale quantum point contact. Low temperature transport measurements of the Hall device reveal a dopant density of 10$^{14}$ cm$^{-2}$, resistance of 2 k$\Omega $/square, and mobility of 30 cm$^{2}$/Vs. The quantum point contact showed a blockaded voltage range of 80 mV, comparable to other similar devices patterned using conventional HDL. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. The work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000. [Preview Abstract] |
Thursday, March 6, 2014 9:36AM - 9:48AM |
S50.00005: Negative Differential Transconductance in Silicon CMOS Quantum Well Field Effect Transistors Clint Naquin, Mark Lee, Hal Edwards, Tathagata Chatterjee, Guru Mathur Quantum well (QW) devices are potentially useful as high-speed oscillators and sensors, as well as high-density memory and multi-state logic. Historically, these devices have been built using III-V heterostructures grown epitaxially in the vertical direction. Silicon CMOS field effect transistors (FETs) that incorporate QWs through the lateral confinement of a silicon inversion layer are of particular interest due to their capability for mass production and industrial scalability. We report on the observation of negative differential transconductance (NDTC) in a set of Si CMOS QW FETs fabricated using industrial 45 nm node processing. Measurements of drain current as a function of gate voltage from 5 K to room temperature were conducted, and local current maxima and minima were observed leading to negative differential transconductance. When voltage-biasing the body terminal, NDTC appears at temperatures as high as 218 K; however, for measurements taken with the body terminal current-biased, NDTC appears at higher temperatures with peak-to-valley ratios (PVR) greater than two. [Preview Abstract] |
Thursday, March 6, 2014 9:48AM - 10:00AM |
S50.00006: Transport spectroscopy and modeling of a clean MOS point contact tunnel barrier Amir Shirkhorshidian, Nathaniel Bishop, Jason Dominguez, Robert Grubbs, Joel Wendt, Michael Lilly, Malcolm Carroll We present transport spectroscopy of non-implanted and antimony-implanted tunnel barriers formed in MOS split-gate structures at 4K. The non-implanted barrier shows no signs of resonant behavior while the Sb-implanted barrier shows resonances superimposed on the clean transport. We simulate the transmission through the clean barrier over the entire gate and bias range of the experiment using a phenomenological 1D-tunneling model that includes Fowler-Nordheim tunneling and Schottky barrier lowering to capture effects at high bias. The model is qualitatively similar to experiment when the barrier height has a quadratic dependence in contrast to a linear one, which can be a sign of 2D effects such as confinement perpendicular to the transport direction. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. This work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Thursday, March 6, 2014 10:00AM - 10:12AM |
S50.00007: Current-current correlations in time domain for a tunnel junction in the quantum regime Karl Thibault, Christian Lupien, Bertrand Reulet We have measured the current fluctuations emitted by a tunnel junction with a very wide bandwidth, from 0.5 to 12 GHz, down to very low temperature T=35mK. This allowed us to perform the spectroscopy (i.e., measure the frequency dependence) of thermal noise (no dc bias, variable temperature), shot noise (low temperature, variable dc voltage bias) and photon-assisted noise (ac bias). Thanks to the very wide bandwidth of our measurement, we can deduce the current-current correlator in time domain. We observe the thermal decay of this correlator as well as its oscillations with a period h/eV, a direct consequence of the effect of the Pauli principle in quantum transport. [Preview Abstract] |
Thursday, March 6, 2014 10:12AM - 10:24AM |
S50.00008: Evidence For Photon Pairing In The Photoassisted Shot Noise Of A Tunnel Junction Jean-Charles Forgues, Christian Lupien, Bertrand Reulet We report the observation of photon pairs in the photo-assisted shot noise of a tunnel junction in the quantum regime, $\hbar \omega \gg k_BT$. This was realised by measuring the correlation between the noise power generated by the junction at two different frequencies, 4.4 and 7.2 GHz, while driving the junction with an ac excitation of variable frequency. We observe clear correlations even when the mean photon number per measurement is smaller than one, a strong evidence for photons being emitted in pairs. These data are in good agreement with predictions based on the fourth cumulant of the current fluctuations generated by the junction. [Preview Abstract] |
Thursday, March 6, 2014 10:24AM - 10:36AM |
S50.00009: An Experimental and Theoretical Investigation of Ultrasound Transmission in Bubbly PDMS Phononic Crystals Caleb Christianson, Saikat Mukhopadhyay, Wolfgang Sachse, Derek Stewart Phononic crystals are two- and three-dimensional structures with a periodic arrangement of two or more materials with different acoustic properties. Depending on the size, structure, and characteristics of the constituent materials, metamaterials with interesting acoustic properties can be formed. These crystals can be used to control the transmission of sound at selected frequencies, focus sound, or serve as waveguides. In this talk, we will focus on the transmission of ultrasonic waves through polydimethylsiloxane (PDMS) films with entrapped air bubbles. Two different theoretical models were used to predict ultrasonic transmission through air-PDMS crystals: (1) a simple scattering model for a series of partially reflective thin films and (2) the code MULTEL, which calculates the transmission using multiple scattering theory. A fabrication process was also developed to stack layers of the crystals with unprecedented alignment. We measured the ultrasonic transmission through the films using the ultrasonic through-transmission mode in a water bath and found an excellent agreement between the measured and calculated transmission. Additionally, we used these models to predict the performance of new phononic structures by scanning a large parameter space and showed how ultrasonic transmission through PDMS layers can be engineered by varying the dimensions, separation, and arrangement of air bubbles. [Preview Abstract] |
Thursday, March 6, 2014 10:36AM - 10:48AM |
S50.00010: Kondo effect in ferromagnetic atomic scale junctions Pavlo Zolotavin, Patrick Wheeler, Douglas Natelson The Kondo effect is one of the hallmark manifestations of electron-electron interactions in solids. Interest to the Kondo effect was reignited recently in connection with quantum dots and molecular junctions. In particular, it was theoretically predicted that when a quantum dot is in the Kondo regime, simultaneous one- and two-quasiparticle scattering results in a universal average quasiparticle charge of (5/3)$e$ that could be measured by shot noise. Experiments in quantum dots and carbon nanotubes have indeed found enhanced noise in the Kondo regime. The abovementioned theoretical prediction and experimental verification were made for a weak-coupling limit, when Kondo temperature, $T_{K},$ amounts to only several degrees. Recently the presence of Kondo resonance with substantially larger $T_{K}$ was demonstrated in mechanical breakjunctions made from ferromagnetic metals. This discovery opens the possibility of testing the validity of the theoretical predictions in the strong coupling limit and in the presence of magnetically correlated electrodes. We will report the results of the ongoing shot noise measurements in ferromagnetic breakjunctions. [Preview Abstract] |
Thursday, March 6, 2014 10:48AM - 11:00AM |
S50.00011: A magnetized quantum wire can act as an optical amplifier Manvir S. Kushwaha We focus on the magnetoplasmon excitations investigated in a quantum wire characterized by a confining harmonic potential and subjected to a perpendicular magnetic field. Essentially, we embark on the device aspects of the intersubband collective (magnetoroton) excitation which observes a negative group velocity between the maxon and the roton. The computation of the gain coefficient suggests an interesting and important application: the electronic device based on such magnetoroton modes becomes capable of amplifying a small optical signal of definite wavelength [J. Appl. Phys. {\bf 109}, 106102 (2011)]. [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