Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session K23: Advances in Scanned Probe Microscopy III: Scanning Probes Spectroscopic TechniquesFocus
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Sponsoring Units: GIMS Room: BCEC 158 |
Wednesday, March 6, 2019 8:00AM - 8:36AM |
K23.00001: Fast nanomechanical spectroscopy: From ions to living cells Invited Speaker: Ricardo Garcia tbd |
Wednesday, March 6, 2019 8:36AM - 8:48AM |
K23.00002: Quantifying Tip-Sample Interactions in Vacuum Using Cantilever-based Sensors: An Analysis Omur Dagdeviren, Chao Zhou, Eric Altman, Udo Dietmar Schwarz We theoretically and experimentally show that the force law obtained from data acquired under vacuum conditions with dynamic force microscopy may deviate more than previously assumed from the actual interaction when the oscillation amplitude of the probe is of the order of the decay length of the force near the surface, which may result in a non-negligible error if correct absolute values are of importance [1]. However, the related inaccuracies can be effectively suppressed by using oscillation amplitudes sufficiently larger than the decay length of the tip-sample interaction. We also propose a novel technique that includes modulating the drive amplitude at a constant height from the surface while monitoring the oscillation amplitude and phase. Ultimately, such amplitude sweep-based force spectroscopy enables shorter data acquisition times and increased accuracy for quantitative chemical characterization compared to standard approaches that vary the tip-sample distance [1, 2]. In addition, since no feedback loop is active while executing the amplitude sweep, the force can be consistently recovered deep into the repulsive regime. |
Wednesday, March 6, 2019 8:48AM - 9:00AM |
K23.00003: Single ion hydrates under the SPM tip Jinbo Peng, Duanyun Cao, Zhili He, Jing Guo, Prokop Hapala, Runze Ma, Bowei Cheng, Ji Chen, Wen Jun Xie, Xin-Zheng Li, Pavel Jelinek, Limei Xu, Yi Qin Gao, En-Ge Wang, Ying Jiang Ion hydration and transport at interfaces are relevant to a wide range of applied fields and natural processes. To correlate atomic structure with the transport properties of hydrated ions, both the interfacial inhomogeneity and the complex competing interactions among ions, water and surfaces require detailed molecular-level characterization. Here we constructed individual sodium ion (Na+) hydrates on a NaCl(001) surface by progressively attaching single water molecules to the Na+ using a combined scanning tunnelling microscopy(STM) and atomic force microscopy(AFM) system. We found that the Na+ hydrated with three water molecules diffuses orders of magnitude more quickly than other ion hydrates. Ab initio calculations revealed that such high ion mobility arises from the existence of a metastable state, in which the three water molecules around the Na+ can rotate collectively with a rather small energy barrier. Our work suggests that anomalously high diffusion rates for specific hydration numbers of ions are generally determined by the degree of symmetry match between the hydrates and the surface lattice. |
Wednesday, March 6, 2019 9:00AM - 9:12AM |
K23.00004: Visualizing mineral-solution interfaces using 3D atomic force microscopy Elias Nakouzi, Benjamin A. Legg, Shuai Zhang, Gregory K Schenter, Jaehun Chun, Andew G. Stack, Christopher J Mundy, Marcel D. Baer, Sebastien Kerisit, James J De Yoreo Understanding processes at solid-liquid interfaces is a key challenge for multiple research fields ranging from surface chemistry and catalysis to bio-membranes and living cells. Recent advances in atomic force microscopy–specifically 3D fast force mapping in amplitude modulated mode–have allowed the direct observation of interfacial solution structure with sub-nanometer resolution. We use this capability to probe multiple mineral-solution systems, including layered silicates (phlogopite and muscovite mica) and aluminum (oxy)hydroxides (boehmite and gibbsite) exposed to salt solutions of different pH and ionic strength. Depending on the system, our data show 3-5 structured layers spaced 0.2–0.5 nm apart and extending ~1.5 nm from the surface, with lateral features templated by the underlying crystal lattice. We compare the results to molecular dynamics simulations and discuss the promises and limitations of this exciting technique. |
Wednesday, March 6, 2019 9:12AM - 9:24AM |
K23.00005: Fast multifrequency measurement of nonlinear conductance Riccardo Borgani, David Haviland We demonstrate fast acquisition of nonlinear current-voltage characteristics (IVC) at every pixel of a high-resolution conductive AFM image [1]. The technique exploits phase-coherent multifrequency lock-in measurement to acquire IVCs on a 512x512 grid in under 9 minutes (trace and retrace), and the inverse Fourier transform to perform the analysis in real time. Our approach overcomes the high resistance of the nanometer-scale tip-surface junction and the stray capacitance of the measurement leads which impose speed limitations (tens of seconds) on the traditional methods of measuring IVCs, making maps of variation over a surface impractical. The measurement technique allows for easy cancellation of parasitic displacement current due to the measurement leads and for separation of the galvanic and displacement currents in the junction. This ultrafast (milliseconds) acquisition of IVCs enables the AFM to reveal nanometer-scale variations in the electrical transport properties of organic photovoltaic and semiconducting thin films. |
Wednesday, March 6, 2019 9:24AM - 9:36AM |
K23.00006: Sub resonance AFM imaging coupled with machine-learning to identify cancer Igor Sokolov, Maxim E Dokukin, Vevekanand Kalaparthi, Milos Miljkovic, Andrew Wang, John Seigne, Petros Grivas, Eugene Demidenko We report on a new approach in diagnostic imaging based on nanoscale-resolution scanning of surfaces of cells collected from body fluids using, sub-resonance AFM tapping, Ringing mode, and machine leaning analysis. The surface parameters, which are typically used in engineering to describe surfaces, are used to classify cells. The method is applied to the detection of bladder cancer, which is one of the most common human malignancies and the most expensive cancer to treat. The method, which utilizes cells collected from urine, shows 94% diagnostic accuracy when examining five cells per patient’s urine sample. It is a statistically significant improvement (p<0.05) in diagnostic accuracy compared to the currently used clinical standard, cystoscopy, as verified on 43 control and 25 bladder cancer patients. Furthermore, the described approach can be extended to detect cell abnormalities beyond cancer as well as to monitor cell reaction to various drugs (nanopharmacology). Thus, this approach may suggest a whole new direction of diagnostic imaging. |
Wednesday, March 6, 2019 9:36AM - 9:48AM |
K23.00007: Visualizing the Electrostatic Barrier of a Material Interface to Nanoscale Dimensions: Defects, Silicides, and Dielectrics Westly Nolting, Jack Rogers, Steven Gassner, Hyeoseon Choi, Vincent LaBella Electrostatic barriers at material interfaces are the foundation of current and futuristic electronic and optoelectronic devices. Direct visualizing of the electrostatic barrier of an interface with nanoscale resolution can be accomplished utilizing ballistic electron emission microscopy (BEEM), an STM-based technique [1]. Tens of thousands of BEEM spectra are acquired on a regularly spaced grid and then fit to extract the Schottky barrier height. Physical and chemical insight is provided by computational modeling, which simulates the distributions of barrier heights and includes effects from the interface and transport of the hot electrons in the metal. This presentation will give an overview of the technique and its ultimate spatial and energetic resolution. Measurements of defects, incomplete silicide formation, the presence of multiple metal species at the interface, monolayer thick dielectric layers, and the influence of ionized impurity scattering in the semiconductor will also be presented. |
Wednesday, March 6, 2019 9:48AM - 10:00AM |
K23.00008: Mapped AFM force spectroscopy on gels: methodological and interpretive developments Greg Haugstad, Guichuan Yu, Ying Chen, Gufa Lin, Alon McCormick, Maggie Zeng We present aqueous-immersion force-distance analysis on fibrin gels and polyvinyl pyrrolidone (PVP) gel-phase coatings. Initial applications were mechanical matching (fibrin to tissue) and lubricity/durability assessment (PVP). In both cases we discovered (a) a need for extensive mapping (tens or hundreds of microns) to survey spatial heterogeneities in both mechanics and topography as well as their correlations; and (b) widely ranging modulus values both among gel samples (~0.1-100 kPa) and across individual gels (one order of magnitude). On the softest PVP gel coatings colloid microprobes were used instead of sharp AFM tips to allow a shear contact (friction characterization). |
Wednesday, March 6, 2019 10:00AM - 10:12AM |
K23.00009: Conductance spectroscopy of confined water in Montmorillonite clay nanoparticles Kelsey Yee, Aydin Wells, N. E. Israeloff Montmorillonite (MNT) clay confines water and ions to few-monolayer sheets. We use an SPM-based nano-dielectric-spectroscopy (NDS) technique to study frequency-dependent (10Hz-10 kHz) electrical properties of individual MNT nanoparticles (NP) with variable water content. We study ionic conductivity in this 2D nano-confined geometry, and compare with bulk material with inter-particle contributions. We focus on the high-frequency (HF) power-law regime of the conductivity peak in the electric modulus, M(f) ~ f1-α, related to a hopping-conductivity, σ ~ σdc + σacfα . We apply a sinusoidal voltage to the conducting tip during non-contact portion of a double pass scan, using high-harmonic for feedback, and the fundamental mode to measure the phase and amplitude of the force-derivative (FD). For a range of relative humidity (RH), the FD phase, φ(f) exhibits a peak, similar to the peak in bulk M(f), but shifted to lower frequencies. We use finite-element-modelling to extract NP conductivity spectra from data (poster by A. Wells). Simulated φ(f) for anisotropically conducting NP have HF power-laws matching M(f). In bulk, for various RH we find exponents, α = 0.3 ±0.05. NP exhibited exponents of α = 0.6 ±0.1. This suggests a different conductivity mechanism in bulk and NP. |
Wednesday, March 6, 2019 10:12AM - 10:24AM |
K23.00010: How Much Information is in an STM Image? Mitchell Yothers, Soumya Bhattacharya, Lloyd Bumm Scanning tunneling microscope (STM) images contain a wealth of information. We are developing real-space post-processing image analysis tools to extract information that would otherwise be hidden. We use decanethiol self-assembled monolayers (SAMs) on Au(111) as our model system. We demonstrate measurements of the “molecule” locations that are in principle accurate to less than 1 pm in any direction. By creating an averaged unit cell image from many imaged unit cells, we also demonstrate that the unit cell image has no additional symmetry beyond its lattice symmetry. Average unit cell images from different structural domains of the same image demonstrate which image features are due to the surface and which are due to the tip. Time-lapse image series of SAMs allow for time averaging techniques to be used to track and study individual molecules. |
Wednesday, March 6, 2019 10:24AM - 10:36AM |
K23.00011: Revealing tip-surface interaction with dynamic force curves Daniel Forchheimer, Riccardo Borgani, David Haviland The force between the AFM tip and the surface is conventionally studied using quasi-static deflection-approach curves. These must be converted into force-position curves by a transformation of coordinates, to be compared with models of the interaction, such as the Derjaguin-Muller-Toporov (DMT) model. For the transformation to be valid the motion has to be slow, as to not excite the resonance of the cantilever. |
Wednesday, March 6, 2019 10:36AM - 10:48AM |
K23.00012: Scanning Tunneling Microscopy and Spectroscopy of Novel Silver-Containing DNA Molecules Natalie Fardian-Melamed, Gennady Eidelshtein, Dvir Rotem, Alexander Kotlyar, Danny Porath The quest for a suitable molecule to pave the way to molecular nano-electronics1 has been met with obstacles for over a decade2, 3. Candidate molecules such as carbon nanotubes lack the appealing trait of self-assembly, while DNA seems to lack the desirable feature of conductivity4. Silver-containing poly(dG)-poly(dC) DNA (E-DNA) molecules were recently reported as promising candidates for molecular electronics5, owing to the selectivity of their metallization, their uniform structure, their resistance to deformation, and their most possible conductivity5, 6. Here we present an elaborate temperature dependent high-resolution morphology characterization of these unique molecules, alongside a detailed depiction of their electronic level structure. Our findings7 were acquired by use of an ultra-high vacuum (UHV) scanning tunneling microscope (STM). The temperature dependence of E-DNA’s topographic features and density of states spurs intriguing insights. Moreover, the energy levels found for E-DNA indicate a novel, truly hybrid metal-molecule structure, potentially more conductive than its DNA-based peers. |
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