Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session K01: Advances in Scanned Probe Microscopy III |
Hide Abstracts |
Sponsoring Units: GIMS Chair: Fereshte Ghahari, NIST/University of Maryland, College Park Room: LACC 150A |
Wednesday, March 7, 2018 8:00AM - 8:12AM |
K01.00001: Charge Fluctuations in Pairs of Silicon Dangling Bonds Thomas Dienel, Wyatt Vine, Mohammad Rashidi, Lucian Livadaru, Jacob Retallick, Taleana Huff, Konrad Walus, Robert Wolkow Several non-contact atomic force microscopy (nc-AFM) techniques have arisen in recent years to study and manipulate atomic species with single electron sensitivity. Thus far, however, this suite of techniques has relied upon the use of thin insulating films to stabilize the charged species and the application of large perturbative fields to control charge. By engineering charge configurations from silicon dangling bonds, which are mid-gap states, and performing all experiments with zero applied bias we bypass these difficulties. Crucially, we find both the contact potential difference and the image charge induced in the tip are required to explain the total tip induced band bending at the semiconductor surface. By employing a series of nc-AFM measurements at different heights, amplitudes, and scan speeds we elucidate the strong distance dependence of these interactions. We demonstrate that with carefully chosen tip-sample separations we can monitor the charge states of dangling bond structures nearly non-perturbatively, revealing surprisingly long sticking times on the order of minutes. |
Wednesday, March 7, 2018 8:12AM - 8:24AM |
K01.00002: Lateral Manipulation of Single Electrons within Atom-Defined Nanostructures via nc-AFM Wyatt Vine, Mohammad Rashidi, Thomas Dienel, Lucian Livadaru, Jacob Retallick, Taleana Huff, Konrad Walus, Robert Wolkow In recent years non-contact atomic force microscopy (nc-AFM) has been used to study and control the charge of surface-supported species by exploiting its atomic resolution and single electron sensitivity. Still, few studies have demonstrated the ability to laterally manipulate charge between single atoms or molecules. We investigate atom-defined charge configurations composed of patterned silicon dangling bonds on a hydrogen-terminated Si(100)-2x1 surface. With the tip-sample separation as our key experimental parameter we uncover two interaction regimes: a strongly interacting regime where we can controllably position single electrons within the structures; and a weakly interacting regime, approximating field-free conditions, where we can track the position of charge within the structures over time. Via atomic manipulation we design symmetric and asymmetric confining potentials; subsequently we demonstrate the ability to strongly enhance the occurrence of ground and excited state charge configurations. |
Wednesday, March 7, 2018 8:24AM - 8:36AM |
K01.00003: Single molecule measurements of fully quantum redox reactions at metal-molecule interface Yoichi Miyahara, Antoine Roy-Gobeil, Kirk Bevan, Peter Grutter We report on the measurements of the electron transfer events in the redox reaction at single molecule–metallic electrode interface, which exhibit the quantized nuclear state transitions mediated by an electron-vibron coupling. We use a sensitive electric charge sensing technique using an atomic force microscopy (AFM) cantilever as a mechanical resonator to detect the electron transfer events [1]. Ferrocene molecules tethered to C16 alkanethiol are adsorbed on a gold surface. We measure the electron transfer that takes place as single-electron tunneling through the C16 alkanethiol at 4 K in vacuum. The electron transfer events appear as the peaks in the bias voltage dependences of the resonance frequency and damping of the AFM cantilever. With increasing oscillation amplitude, the intensity of the observed peak increases and then exhibits a series of peaks which are indicative of vibronic excitation. The evolution of the peak shape can be explained by the single-electron tunneling model which takes into account the overlap integral of the nuclear wave functions of two charge states (Franck-Condon factor). The experimental spectra show a very good agreement with the theoretical ones. [1] Y. Miyahara, A. Roy-Gobeil and P. Grutter, Nanotechnology 28, 064001 (2017). |
Wednesday, March 7, 2018 8:36AM - 8:48AM |
K01.00004: Scanning diamond NV center probes compatible with conventional AFM technology Tony Zhou, Rainer Stohr, Amir Yacoby Scanning probe microscopy using nitrogen vacancy (NV) centers in diamond has become a versatile tool with applications in physics, chemistry, life sciences, and earth and planetary sciences. However, the fabrication of diamond scanning probes with high photon collection efficiency, NV centers with long coherence times, and integrated radio frequency (RF) remains challenging due to the small physical dimensions of the probes and the complexity of the fabrication techniques. In this work, we present a simple and robust method to reliably fabricate probes that can be integrated with conventional quartz tuning fork based sensors as well as commercial silicon AFM cantilevers. An integrated RF micro-antenna for NV center spin manipulation is directly fabricated onto the probe making the design versatile and compatible with virtually all AFM instruments. This integration marks a complete sensor package for NV center-based magnetometry and opens up this scanning probe technique to the broader scientific community. |
Wednesday, March 7, 2018 8:48AM - 9:00AM |
K01.00005: Quantum Force Measurements Using Macroscopic Molecular Tunneling Yi-Ting Chen, Dominik Rastawicki, Yang Liu, Hari Manoharan Microscopic force sensing is at the center of many technologies, such as atomic force microscope, inertial sensor and pressure sensor. While the stress or Van der Waals force are measured by these sensors, Casimir force is in the same scope but seldom probed experimentally. Casimir force arises from the alteration of boundary in zero point electromagnetic field, as predicted by quantum field theory. In condensed matter, alternation of the electronic wave function on a metallic surface also causes forces between nano structures under the same principle. We present a technique to measure this electron-mediated force between atomic objects using scanning tunneling microscope. Unlike Van der Waals force, this force is a strong function of geometry. The force is measured under different geometrical designs. The results are consistent with theoretical calculations. |
Wednesday, March 7, 2018 9:00AM - 9:12AM |
K01.00006: Development of low temperature scanning probe microscope for electrostatic force measurements on LaAlO3/SrTiO3 interface devices Aaveg Aggarwal, Venkat Chandrasekhar A low temperature scanning probe microscope (SPM) is a powerful instrument to study a wide variety of effects in solid state systems. Simultaneous SPM and transport measurements are a great tool for probing new and unknown physics. Our goal is to study novel emergent phenomena in complex oxide heterostructures, in particular, LaAlO3/SrTiO3 interface devices. With this goal in mind, we report on our progress in developing a SPM that can be cooled down to sub-kelvin temperatures in a dilution refrigerator, capable of carrying out simultaneous transport and electrostatic force microscopy, scanning capacitance microscopy and scanning gate microscopy measurements. |
Wednesday, March 7, 2018 9:12AM - 9:24AM |
K01.00007: Effects of SQUID Alignment on Penetration Depth Measurements Irene Zhang, John Kirtley, Christopher Watson, Hilary Noad, Kathryn Moler Scanning SQUID (Superconducting QUantum Interference Device) susceptometry is a powerful tool for measuring a sample’s response to a small, local magnetic field. For example, measuring the diamagnetic susceptibility due to a superconductor as a function of height yields information about the local penetration depth. In our susceptometer geometry, this is accomplished by passing an alternating current through a field coil, then phase sensitively measuring the resulting flux through a smaller concentric pickup loop. The result is then reported in units of flux per ampere of current applied, which is an inductance. Normalizing this figure by the unloaded mutual inductance between the field coil and pickup loop results in a dimensionless susceptibility that depends sensitively on the sample as well as the measurement geometry. In this talk, we discuss the systematic errors introduced by geometric factors such as the sensor height, pitch, and roll in extracting the penetration depth from scanning SQUID susceptometry data, providing insight into the interpretation of future measurements. |
Wednesday, March 7, 2018 9:24AM - 9:36AM |
K01.00008: Fabrication and Characterization of sub-100nm Pb SQUIDs for nanoscale SQUID-on-Tip Microscopy Avi Shragai, Marec Serlin, Charles Tschirhart, Martin Huber, Andrea Young Scanning nanoSQUID-on-tip (nSOT) microscopy is a highly sensitive probe of local magnetic field. Unlike traditional microSQUID microscopy and other nanoscale scanned probes, nSOTs provide noninvasive magnetic imaging at sub-100nm length scales while operating in ambient magnetic fields as large as several Tesla (Vasyukov et al. Nature Nano. 8:639-644). I will describe the process for fabricating high-sensitivity nSOTs on the tip of a pulled quartz pipette, including the construction of a home-built thermal evaporator for self-aligned, three-angle deposition of a superconducting Pb film at cryogenic temperatures. Using this instrument, and an associated 4.2K squid-array amplifier based characterization set-up, we achieve reliable production of nSOTs with effective diameter as small as 40nm and spin-sensitivity of approximately 3μB/√Hz that remain functional in magnetic fields over 1T. |
Wednesday, March 7, 2018 9:36AM - 9:48AM |
K01.00009: Construction of a 4.2 K Scanning NanoSQUID-on-Tip Microscope Incorporating Topographic Feedback Charles Tschirhart, Marec Serlin, Avi Shragai, Jiacheng Zhu, Martin Huber, Andrea Young Scanning probe techniques provide access to local information not obtainable from bulk measurements of thermodynamic properties or transport. Nanoscale SQUIDs fabricated on the ends of quartz pipettes have recently emerged as high sensitivity cryogenic magnetometers and thermometers capable of providing the spatial resolution necessary for investigating mesoscopic transport phenomena. |
Wednesday, March 7, 2018 9:48AM - 10:00AM |
K01.00010: Scanning SQUID microscopy in a cryogen-free dilution refrigerator David Low, George Ferguson, Rachel Resnick, Brian Schaefer, Alexander Jarjour, Eric Smith, Katja Nowack Scanning probe microscopy in cryogen-free refrigerators is challenging due to vibrations introduced by the cryocooler. We have implemented a magnetic flux microscope using a scanning superconducting quantum interference device (SQUID) in a cryogen-free dilution refrigerator with a base temperature of 10 millikelvin. We report on our design of the microscope and present progress toward a detailed analysis of the vibrations in the system. These include vibrations of the cold plates in the refrigerator measured with geophones and sample-to-probe vibrations obtained from analyzing noise spectra near a localized source of magnetic field. Following Schiessl et al. (Appl. Phys. Lett. 109, 232601 (2016).), we can determine the x, y, and z components of the sensor-sample vibrations. Finally, we discuss strategies to further reduce vibrations in our refrigerator. |
Wednesday, March 7, 2018 10:00AM - 10:12AM |
K01.00011: Remote Bias Induced Electrostatic Force Microscopy for Subsurface Imaging Joseph Kopanski, Lin You, Yaw Obeng Contrast in electrostatic force microscopy (EFM) depends on the electrostatic force between the tip and sample. In the related technique, scanning Kelvin force microscopy (SKFM), contrast arises from the force due to the capacitance gradient with tip-to-sample distance (dC/dz). Since these forces act over long distances, EFM can image structures beneath the sample surface. The measured quantities arise from variations in sample dielectric constant, any charge accumulated on subsurface structures or interfaces, and subsurface variations in conductivity. Using subsurface structures that could be independently biased, we were able to implement a mode of EFM where the AC+DC signal was applied to the buried structures instead of the cantilever. An external high frequency lock-in amplifier (LIA) monitors the deflection signal of the cantilever, using the AC signal applied to the buried structure as its reference. Small changes in the phase of the cantilever oscillation can then be detected to map subtle electrostatic force variation between the subsurface metal lines and the EFM tip. Our technique allows us to separate the effect of buried charge and capacitance gradient. By applying a backing potential to the substrate, the subsurface resolution can be enhanced. |
Wednesday, March 7, 2018 10:12AM - 10:24AM |
K01.00012: Subsurface imaging using tip generated stress and electric fields in atomic force microscopy Maria Cadena, Yuhang Chen, Ronald Reifenberger, Arvind Raman It is well known that subsurface nano-objects can be detected by Atomic Force Microscopy (AFM) with either stress or electric fields by using resonance-enhanced dynamic AFM methods, such as Contact Resonance AFM (CR-AFM) or 2nd-harmonic Kelvin Probe Force Microscopy (KPFM), respectively. However, little is understood regarding the relative differences between the two methods. We present a head-to-head comparison between the subsurface imaging capabilities of these two methods through experiments and computational models based on finite element analysis (FEA). High resolution subsurface images are obtained using both techniques from an identical area of a polymer composite film. The film contains single-walled carbon nanotube networks embedded in a polyimide matrix. The depth of the buried carbon nanotube bundles is estimated by combining experiments and FEA. The results obtained by CR-AFM (depth 33.7 ± 2.6 nm) and KPFM (depth 29.1 ± 2.8 nm) are in good agreement. Both techniques exhibit similar depth sensitivity while CR-AFM has a higher lateral resolution. |
Wednesday, March 7, 2018 10:24AM - 10:36AM |
K01.00013: Optically Coupled Methods for Microwave Impedance Microscopy Scott Johnston, Eric Ma, Zhi-Xun Shen Scanning Microwave Impedance Microscopy (MIM) measurement of photoconductivity with 50 nm resolution is demonstrated using a modulated optical source. The use of a modulated source allows for measurement of photoconductivity in a single scan without a reference region on the sample, as well as removing most topographical artifacts and enhancing signal to noise as compared with unmodulated measurement. A broadband light source with tunable monochrometer is then used to measure energy resolved photoconductivity with the same methodology. Finally, a pulsed optical source is used to measure local photo-carrier lifetimes via MIM, using the same 50 nm resolution tip. |
Wednesday, March 7, 2018 10:36AM - 10:48AM |
K01.00014: Direct Mapping of Localized Noise Sources in Monolayer MoS2 Myungjae Yang, Tae-Young Kim, Takhee Lee, Seunghun Hong Electrical noises in MoS2-based conducting channels have been extensively studied by measuring the current noises from MoS2-based devices. However, it has been very difficult to directly map the sources of such electrical noises in the channels. Herein, we report a method to directly map localized noise sources and their activities in a monolayer MoS2 with a nanoscale resolution. In this method, currents and noises were measured through a conducting atomic force microscopy probe which made a direct contact on the monolayer MoS2. By analyzing the measured data, we could estimate sheet resistance and noise source activities in the grain structures of the MoS2, revealing clear correlations between them. In addition, we measured the effect of lights on noise sources activities inside MoS2. Our results provide a valuable insight about noise source activities in MoS2 and can be utilized for various electrical noise researches. |
Wednesday, March 7, 2018 10:48AM - 11:00AM |
K01.00015: Simulations of atomic force microscopy image “flickering” on a doped Si (111) 7x7 surface using real-space pseudopotential calculations. Dingxin Fan, James Chelikowsky, Daniel Meuer, Franz Giessibl Recently a “flickering” phenomena has been reported using atomic force microscopy (AFM) imaging applied to a heavily B doped Si (111) 7x7. The flickering corresponds to a brightening and dimming image of the Si adatoms as the AFM tip height is changed. We employ real-space pseudopotential-density functional theory calculations to address this phenomenon. We consider stable structures of B doped Si structures with and without a CO-functionalized AFM tip. We find a bistable configuration of the B doped Si system with the presence of CO tip, which may account for the observed image changes. |
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