Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session R01: Advances in Scanned Probe Microscopy IV |
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Sponsoring Units: GIMS Chair: Christopher Gutierrez, Univ British Columbia Room: LACC 150A |
Thursday, March 8, 2018 8:00AM - 8:12AM |
R01.00001: Three-Dimensional sub-10 nm resolution using Bessel Beam Microscopy Chumki Chakraborty, Craig Snoeyink In Optical microscopes, determining the three-dimensional information from a two-dimensional view is a challenging task. Even if this information is extracted by optics manipulation, diffraction of light limits the resolution of optical microscopes to ~200 nm and ~500 nm in the lateral and axial directions, respectively. In our group, an optical super-resolution microscopy system, based on Bessel Beam has been developed. A Gaussian light beam is converted to Bessel Beam from which, the three-dimensional information of optical images is obtained. With this simple optical manipulation, a sub-10 nm resolution has been achieved in both lateral and axial directions. In the talk, details of the novel microscopy set up and results from the resolution testing experiments will be presented. Also, methods to tackle the effect of optical distortions on this microscopy system, using Adaptive Optics will be discussed, which can further improve the resolution as well as photon efficiency. |
Thursday, March 8, 2018 8:12AM - 8:24AM |
R01.00002: Enhancing Microscopy through Deep Learning Yair Rivenson, Zoltán Göröcs, Harun Günaydin, Yibo Zhang, Hongda Wang, Aydogan Ozcan Extending the field of view, depth of-field and resolution of images acquired using a microscope is the end goal of various techniques involving different combinations of hardware and/or software improvements. Here, we demonstrate that a convolutional deep neural network can enhance optical microscopy images, without any hardware modification to the microscope. For this aim, a deep network is trained using experimentally acquired high-resolution and low-resolution microscopic images of different samples. Following its training, the deep network remains fixed and rapidly outputs an image with enhanced resolution, matching the performance of a high numerical aperture objective lens, while also significantly advancing its limited field-of-view and depth-of-field. This deep learning based framework can be broadly applied to imagers at different parts of the electromagnetic spectrum and it demonstrates the potential of convolutional neural networks for solving inverse problems in imaging, which is especially important when accurate modeling of the light-matter interaction is a challenging task. |
Thursday, March 8, 2018 8:24AM - 8:36AM |
R01.00003: Phase Retrieval and Hologram Reconstruction Using a Neural Network Yair Rivenson, Yibo Zhang, Harun Günaydin, Da Teng, Aydogan Ozcan The ability to recover the missing phase information of waves has been transformative for a wide set of fields, such as material science and life sciences, leading to numerous scientific discoveries so far. Here, we demonstrate that a deep convolutional neural network can achieve phase retrieval and holographic image reconstruction, using a single intensity-only hologram of a complex sample, which conventionally required multiple measurements for phase recovery. Using a trained convolutional neural network, phase recovery and holographic image reconstruction of a complex-valued sample are performed in a single feed-forward pass, considerably reducing the measurement and the computation time when compared to measurement diversity based phase recovery approaches. We validated this approach by imaging various samples including blood and Pap smears and tissue samples. The results demonstrate the potential of convolutional neural networks for solving challenging inverse problems in computational imaging field. |
Thursday, March 8, 2018 8:36AM - 8:48AM |
R01.00004: XTIP - A New Dedicated Beamline for Synchrotron X-ray Scanning Tunneling Microscopy Volker Rose, Nozomi Shirato, Saw-Wai Hla, Ruben Reininger, Mike Fisher Recently, substantial progress was made on Argonne’s Synchrotron X-ray Scanning Tunneling Microscopy (SX-STM) project. In particular, we demonstrated the power of SX-STM for elemental characterization of individual nano-islands with single atom height sensitivity, developped a new smart tip concept, and demonstrated imaging of nanoscale magnetic domains. Further substantial advances are expected using the new low temperature (LT) SX-STM system. |
Thursday, March 8, 2018 8:48AM - 9:00AM |
R01.00005: Buried Interface Magnetism and Near Edge X-ray Absorption Fine Structures Probed by Synchrotron X-ray STM Hao Chang, Nozomi Shirato, Marvin Cummings, Daniel Rosenmann, John Freeland, Volker Rose, Saw Hla Synchrotron X-ray STM (SXSTM) combines two of the most powerful materials characterization techniques, synchrotron X-ray and STM. SXSTM has a great potential revolutionize material characterizations with simultaneous elemental, magnetic and topological contrast down to the atomic scale. Here, we present our recent SXSTM results of nanoscale materials measured at the APS of Argonne National Lab. Based on SXSTM X-ray absorption spectroscopy, by employing circular polarized X-rays, we are able to demonstrate X-ray magnetic circular dichroism of LSMO/LNO superlattices at low temperature. Polarization dependent x-ray absorption spectra have been obtained through a specially fabricated tip that captures photo-electrons. Unlike conventional spin-polarized STM, x-ray excitations provide magnetic contrast even with a non-magnetic tip. Here we demonstrate the buried magnetism at LNO/LSMO interface by analyzing the XMCD and near edge X-ray absorption fine structure. Without magnetic field, the magnetism is completely induced by the LNO/LSMO interface through charge transfer and interfacial strain. In contrast, LSMO/LNO superlattice does not present interfacial magnetism. In addition to presenting the recent results, we will also discuss potential future research directions using SXSTM. |
Thursday, March 8, 2018 9:00AM - 9:12AM |
R01.00006: Nanoscale Visualization of Schottky Barrier Interfaces with Ballistic Electron Emission Microscopy Westly Nolting, Jack Rogers, Steven Gassner, Dan Pennock, Joshua Goldberg, Vincent LaBella Visualizing the electrostatics of a buried interface to nanoscale resolution can be accomplished with Ballistic Electron Emission Microscopy (BEEM), an STM based technique[1-2]. In this work, we measure and model the nanoscale fluctuations in the electrostatics of metal semiconductor interfaces. Assorted metal/silicon and silicide/silicon systems are studied to determine the Schottky barrier height and its nanoscale fluctuations. This is accomplished by acquiring tens of thousands of BEEM spectra on a regularly spaced grid and fitting the results to determine the Schottky barrier height. Computational modeling is utilized to simulate the distributions of barrier heights that includes effects from the interface and transport of the hot electrons in the metal. Agreement between the model and data provides insight into effects that disturb the Schottky barrier height such as: incomplete silicide formation, the presence of multiple metal species at the interface, and the influence of ionized impurity scattering in the semiconductor. |
Thursday, March 8, 2018 9:12AM - 9:24AM |
R01.00007: Nanoscale Electrochemistry via Lithium Focused Ion Beam William McGehee, Evgheni Strelcov, Jamie Gardner, Saya Takeuchi, Oleg Kirrilov, Vladimir Oleshko, David Gundlach, Christopher Soles, Nikolai Zhitenev, Jabez McClelland We report progress in developing Li+ focused ion beams (FIB) as a novel probe for exploring nanoscale electrochemistry in battery-relevant materials. This work focuses on implantation of lithium ions in crystalline silicon to benchmark this technique and builds on recent, qualitative studies of FIB implantation in Sn microspheres [Takeuchi et al. JES 163 (6), A1010-A1012]. FIB implantation opens the possibility of precise spatial control of nanoscale lithium concentration though variation of the beam positioning and current. Experiments are performed in vacuo without the presence of electrolytes or associated solid-electrolyte interface. The Li+ ion beam operates with energies ranging from 0.5 to 5 keV, currents up to 15 pA, and minimum spot size of 27 nm using a magneto-optical trap ion source (MOTIS). |
Thursday, March 8, 2018 9:24AM - 9:36AM |
R01.00008: In-situ quantum transport measurement system in the milliKelvin range Shimin Cao, Chaoyi Cai, Chuanwu Cao, Zhijian Xie, Guangyi Chen, Shaomian Qi, Jianhao Chen We will present the design, development and performance of an ultra-high vacuum (UHV) in-situ quantum transport measurement facility operating at a base temperature at the milliKelvin range in magnetic field up to 14 Tesla. The system is capable of in-situ bottom sample exchange with single-axle sample rotation for tilted field measurement. Multiple species of ions, atoms and molecules can be controllably absorbed on or implanted into the sample surface during a single experiment on a single device. The system also includes a complete set of UHV chambers and an inertial gas filled glove box for sample preparation, device fabrication, room temperature sample measurement and doping, as well as the transport of the removable sample stage within the system. To show how the equipment functions, we will demonstrate the evolution of Shubnikov–de Haas oscillation, quantum Hall states and the apparent Berry phase of graphene as a function of different types of impurities, absorbed on the sample during the transport measurement at low temperature. |
Thursday, March 8, 2018 9:36AM - 9:48AM |
R01.00009: Single-Crystalline Micro-Oscillators: Elastic Constants in Strongly Correlated Electron Systems on the Micrometer Scale Amelia Estry, Maja Bachmann, Toni Helm, Philip Moll The elastic moduli are second derivatives of the free energy with respect to strain, and therefore thermodynamic constants that can probe symmetry breaking at phase transitions. We propose a new measurement technique based on resonant measurements of elastic micro-resonators. By using a Focused Ion Beam (FIB), we cut micro-cantilevers with precisely known orientations and geometries along selected crystal directions from small single crystals. With the FIB, we can create thin cantilevers in the micron scale to explore single domains and domain walls – a capability unique to this technique. These cantilevers are excited by a piezo-electric transducer and the resonance frequencies are detected optically, such that the elastic moduli can be directly calculated from the eigenfrequencies as a function of magnetic field and temperature. This novel technique can provide symmetry-resolved information that is useful in exploring nematicity in materials such as iron-based superconductors and the pseudo-gap in underdoped cuprates. Moreover, finite-element based simulations will be used to determine the elastic constants via the resonance frequencies of various cantilever geometries. |
Thursday, March 8, 2018 9:48AM - 10:00AM |
R01.00010: Cryogenic imaging of metal-insulator transitions and quantum hall edge states using a commercial Atomic Force Microscope with Scanning Microwave Impedance Microscopy (sMIM) Yongliang Yang, Oskar Amster We report the instrumentation and experimental results of a cryogenic scanning microwave impedance microscope, which is now commercially available from PrimeNano Inc. The microwave probe, cryogenic amplifier, and positioning/scanning stages are located inside the variable temperature insert of a helium cryostat equipped with a superconducting magnet. Both contact mode and height-modulation mode scanning (using shielded cantilever probes) have been achieved. At temperatures down to 4 K and magnetic fields up to 9 T, the system has demonstrated the ability to spatially resolve the metal–insulator transition in a doped silicon sample, the quantum Hall edge states in graphene with a BN capping layer, and the conducting magnetic domain walls in polycrystalline Nd2Ir2O7. The data can be quantitatively analyzed by finite element simulation. Effects of the thermal energy and electric fields on local charge carriers can be seen in the images taken at different temperatures and dc biases. Electrical imaging in the microwave regime down to the liquid helium temperature opens up a new avenue to probe complex materials and phase transitions in the nanometer length scale under various conditions. |
Thursday, March 8, 2018 10:00AM - 10:12AM |
R01.00011: Scattering-Type Scanning Near-Field Optical Microscopy for Optical Microscopy and Spectroscopy at the Nanoscale Max Eisele, Adrian Cernescu, Nicolai Hartmann Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) is a scanning probe approach to optical microscopy and spectroscopy bypassing the ubiquitous diffraction limit of light to achieve a spatial resolution below 10 nanometer. s-SNOM employs the strong confinement of light at the apex of a sharp metallic AFM tip to create a nanoscale optical hot-spot. Analyzing the scattered light from the tip enables the extraction of the optical properties (absorption, reflectivity) of the sample directly below the tip and yields nanoscale images simultaneous to topography. In addition to near-field microscopy the technology has been advanced to enable hyperspectral, nanoscale Fourier-transform spectroscopy (nano-FTIR) using broadband radiation from the far-infrared to the visible spectral range. This presentation will summarize the latest achievements in the in the field of near-field microscopy and spectroscopy on polymers, biomaterials and 2D materials. In addition, the combination of near-field microscopy with ultrafast pump-probe experiments will be discussed opening a complete new approach solid-state physics where intriguing phenomena like surface plasmons polaritons or carrier relaxation dynamics can be observed with a combined <200fs temporal and <20nm spatial resolution. |
Thursday, March 8, 2018 10:12AM - 10:24AM |
R01.00012: Phase Contrast in Scanning Transmission Electron Microscopy with Nanostructured Phase Gratings Tyler Harvey, Colin Ophus, Fehmi Yasin, Jordan Chess, Jordan Pierce, Benjamin McMorran Off-axis electron holography, which uses an electrostatic biprisim to interfere electrons transmitted through a specimen with a reference wave, has for many years been the premier technique for retrieving the phase of electrons. With holography, one can both reconstruct long-range electric and magnetic fields [1], and map the charge distribution in a nanowire [2]. However, the resolution of off-axis electron holography is fundamentally limited because interference fringes are recorded in real space; standard reconstruction of the phase has a resolution on the order of the fringe spacing. |
Thursday, March 8, 2018 10:24AM - 10:36AM |
R01.00013: Nanoprinting of Metallic Conductive Inks with Fountain Pen Nanolithography Aaron Lewis, Talia Yeshua, Rimma Dechter, Uwe Huebner, Shlomo Magdassi, Michael Layan Printing of conductive metallic lines with widths as small as 15 nm can be controlled up to a few µm by using Fountain Pen Nanolithography (FPN). The FPN technique is based on a force sensing bent nanopipette and the printing with force feedback is similar to a pen in the nano regime. The geometry of the nanopen and atomic force microscopy system used allows the placement of the printing tip with the highest of optical resolutions. Any desired location can be rapidly accessed with sub-micrometer precision. Using this nanopen, investigations of various inks were undertaken together with instrumental and script-tool development. This led to the printing of conductive lines using inks composed of silver nanoparticles and salt solutions of silver and copper. In addition, it is shown that printing over structures with varying heights and material characteristics is achievable without changing the line dimensions. The line widths are varied by using nanopens with different orifices or by tailoring wetting properties of the ink on the substrate. Metallic interconnections of conducting lines are reported with a conductivity of up to 0.45% of bulk silver. The results demonstrate both conductive lines and electrical interconnections can be printed at scales presently not being addressed. |
Thursday, March 8, 2018 10:36AM - 10:48AM |
R01.00014: Atomic magnetometer-based high-sensitivity multichannel magnetic sensor Young Jin Kim, Igor Savukov Multichannel parallel magnetic measurements are required for various applications in many fields such as neuroscience and biomedical research. The leading high-sensitivity multichannel sensors are based on arrays of a low-temperature superconducting quantum interference device (SQUID) magnetometer, which presents multiple technological challenges mainly due to cryogenic operation and a high cost. In order to improve the current technologies of multichannel sensors, we recently constructed a highly sensitive 16-channel magnetic sensor based on an atomic magnetometer. The multichannel operation is based on a single large Rb vapor cell, two broad laser beams, and a two dimensional photodiode array. In this talk, we will describe the basic principle and the design of our multichannel sensor. We experimentally demonstrate that each channel of the sensor has a high sensitivity of a few tens femtotesla at low frequency. We anticipate that this sensor will be useful for many applications. |
Thursday, March 8, 2018 10:48AM - 11:00AM |
R01.00015: Multidimensional Mapping of Electrical properties using Fast Force Volume Peter De Wolf, Zhuangqun Huang, Bede Pittenger, Mickael Febvre, Denis Mariolle, Nicolas Chevalier AFM-based property mapping modes such as Force Volume & PeakForce Tapping provide force spectra at each pixel enabling detailed mechanical characterization. In this work, the force spectra are augmented by also acquiring electrical spectra for every pixel of the image. During each force-distance cycle, a ‘hold segment’ is inserted during which a fixed force is applied and electrical spectra are collected by ramping certain electrical operating parameters. This results in multi-dimensional datacubes whereby electrical & mechanical spectra are present for each pixel. Optimization of the force mapping movements and the electrical measurement setup allowed us to maintain a relatively high imaging speed (typ. 20-100 ms/pixel). The approach is illustrated by four modes: In C-AFM, I-V spectra in each pixel are acquired by ramping the DC bias. The resulting datacube is used to extract high-resolution current barrier property maps. Applied to SCM and sMIM, dC/dV-V and C-V spectra are acquired. In PFM either switching loops or contact resonance spectra are obtained. Investigation of a variety of materials illustrates the capability to reveal sample properties which are not accessible or easily missed in conventional methods where maps at only one or a few discrete settings are acquired. |
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