Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session A46: Advances in Scanning Probe Microscopy I: Novel Approaches and Ultrasensitive DetectionFocus
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Sponsoring Units: GIMS Chair: Hongwoo Baek, National Magnet Laboratory Room: 311 |
Monday, March 14, 2016 8:00AM - 8:12AM |
A46.00001: AFM cantilever vibration detection with a transmitted electron beam Taylor Woehl, Ryan Wagner, Robert Keller, Jason Killgore Cantilever oscillations for dynamic atomic force microscopy (AFM) are conventionally measured with an optical lever system. The speed of AFM cantilevers can be increased by decreasing the size of the cantilever; however, the fastest AFM cantilevers are currently nearing the smallest size that can be detected with the current optical lever approach. Here we demonstrate an electron detection scheme in an SEM for detecting AFM cantilever oscillations. An oscillating AFM tip is positioned perpendicular to the propagation direction of a stationary $\approx $ 1 nm diameter electron probe, and the oscillatory change in electron scattering resulting from the changing thickness of the electron irradiated area of the AFM tip is detected with a transmitted electron detector positioned below the AFM tip. We perform frequency sweep and ring-down experiments to determine the first resonant frequency and Q factor of an AFM cantilever. [Preview Abstract] |
Monday, March 14, 2016 8:12AM - 8:24AM |
A46.00002: Innovative SPM Probes for Energy-Storage Science: MWCNT-Nanopipettes to Nanobattery Probes Jonathan Larson, Alec Talin, Alexander Pearse, Alexander Kozen, Janice Reutt-Robey As energy-storage materials and designs continue to advance, new tools are needed to direct and explore ion insertion/de-insertion at well-defined battery materials interfaces. Scanned probe tips, assembled from actual energy-storage materials, permit SPM measures of local cathode-anode (tip-sample) interactions, including ion transfer. We present examples of ``cathode'' MWCNT-terminated STM probe tips interacting with Li(s)/Si(111) anode substrates. The MWCNT tip functions as both SPM probe and Li-nanopipette,$^{\mathrm{[1]}}$ for controlled transport and manipulation of Li. Local field conditions for lithium ionization and transfer are determined and compared to electrostatic models. Additional lithium metallic and oxide tips have been prepared by thin film deposition on conventional W tips, the latter of which effectively functions as a nanobattery. We demonstrate use of these novel probe materials in the local lithiation of low-index Si anode interfaces, probing local barriers for lithium insertion. Prospects and limitations of these novel SPM probes will be discussed. [1] J.M. Larson et al, Small, 2015, DOI: 10.1002/smll.201500999 [Preview Abstract] |
Monday, March 14, 2016 8:24AM - 8:36AM |
A46.00003: Carbon nanotube/carbon nanotube composite AFM probes prepared using ion flux molding Grace Chesmore, Carrollyn Roque, Richard Barber The performance of carbon nanotube-carbon nanotube composite (CNT/CNT composite) atomic force microscopy (AFM) probes is compared to that of conventional Si probes in AFM tapping mode. The ion flux molding (IFM) process, aiming an ion beam at the CNT probe, aligns the tip to a desired angle. The result is a relatively rigid tip that is oriented to offset the cantilever angle. Scans using these probes reveal an improvement in image accuracy over conventional tips, while allowing higher aspect ratio imaging of 3D surface features. Furthermore, the lifetimes of CNT-CNT composite tips are observed to be longer than both conventional tips and those claimed for other CNT technologies. Novel applications include the imaging of embiid silk. [Preview Abstract] |
Monday, March 14, 2016 8:36AM - 9:12AM |
A46.00004: Nanometer-scale scanning magnetometry of spin structures and excitations using Nitrogen-vacancy centers Invited Speaker: Yuliya Dovzhenko The development of increasingly sensitive scanning techniques has led to new insights into the physics of interacting condensed matter systems. Recently, Nitrogen-Vacancy (NV) centers in diamond emerged as a promising scanning magnetic imaging platform capable of operating in a broad range of temperatures and magnetic fields, with sensitivity and resolution capable of imaging a single electron spin with sub-nanometer resolution under ambient conditions [1,2]. In this talk we will review some of the recent developments in this new scanning platform. We will describe our recent progress in using a single NV center in a scanning diamond nano-pillar to study condensed matter magnetism at both room and low temperatures. In particular, we demonstrate the use of scanning NV magnetometry to image stray fields originating from static chiral spin structures, as well as to detect resonant and off-resonant low-energy spin excitations [3].~ [1] Grinolds et al., Nature Phys 9, 215 (2013) [2] Grinolds et al., Nature Nanotech. 9, 279 (2014) [3] Van der Sar et al., Nature Comm. 6, 7886 (2015) [Preview Abstract] |
Monday, March 14, 2016 9:12AM - 9:24AM |
A46.00005: Nanoscale imaging of paramagnetic spin labels using a single spin in diamond. Amila Ariyaratne, Bryan Myers, Matthew Pelliccione, Ania Jayich Spin-labeling molecules with paramagnetic species is a powerful technique for probing molecular structure. However, current techniques are ensemble measurements, inherently lacking the sensitivity to detect a single spin or the conformational properties of a single biomolecule. In this talk, we demonstrate an imaging technique that has the promise of single-spin imaging and ultimately molecular structure imaging. We present two-dimensional nanoscale imaging of a monolayer of gadolinium (Gd) atomic spin labels at ambient conditions. The sensing element is a single nitrogen-vacancy (NV) center in diamond. A patterned monolayer of Gd atoms self-assembled on a Si atomic force microscopy tip is controllably interacted with and detected by the NV center. The fluctuating magnetic field generated by GHz-scale Gd spin flips relaxes the NV center in a manner that depends strongly on the Gd-NV separation. Using this technique, we demonstrate a Gd-induced reduction of the T1 relaxation time of the NV center with nm spatial resolution. Our results indicate that nanometer-scale imaging of individual electronic spins at ambient conditions is within reach. This will ultimately enable the study of structural and functional studies of single biomolecules in their native, folded state. [Preview Abstract] |
Monday, March 14, 2016 9:24AM - 9:36AM |
A46.00006: ABSTRACT WITHDRAWN |
Monday, March 14, 2016 9:36AM - 9:48AM |
A46.00007: How to simultaneously scan connected tips in a dual-tip STM Wan-Ting Liao, Michael Dreyer, James Anderson, Christopher Lobb, Frederick Wellstood Starting with a dual independent-tip scanning tunneling microscope (STM) design [1], we have connected the two tips by a short ($\sim$3 mm) flexible Nb foil strip that was patterned by a laser. To enable simultaneous imaging with both tips, we move both tips to within tunneling distance of a surface and modulate one tip's z-piezo at $\sim$ 5 kHz and the other at$\sim$10 kHz. The resulting combined tunneling current from the system has modulation at both frequencies, which we detect using two lock-in amplifiers. The two outputs (dI/dz1 and dI/dz2) are feedback to individual STM electronic controllers to allow simultaneous topographic imaging using both tips. We tested our setup at room temperature using Pt-Ir tips on Au/Mica and HOPG samples. The next step is to operate this dual-tip STM at 30 mK on a superconducting sample so that the device forms a novel type of scanning SQUID. Holding one of the tips fixed as a reference junction, the other tip will be scanned to image the gauge-invariant phase difference of a superconductor at the atomic scale [2]. [1] A. Roychowdhury, et al., Rev. Sci. Inst. 85, 04.706(2014) [2]D. F. Sullivan, et al., J. Appl. Phys. 113,183905 (2013) [Preview Abstract] |
Monday, March 14, 2016 9:48AM - 10:00AM |
A46.00008: High-resolution imaging of interfacial water by noncontact atomic force microscopy. Jinbo Peng, Jing Guo, Prokop Hapala, Duanyun Cao, Pavel JelĂnek, Limei Xu, Enge Wang, Ying Jiang Resolving the hydrogen-bonding configuration of water on the solid surfaces with atomic-scale precision is crucial in water science yet it remains challenging. Recently we have shown the possibility of attacking this problem by STM based on the submolecular orbital imaging of water. However, STM mainly probes the spatial distribution of the density of states near the Fermi level, thus is not sensitive to the chemical structure of molecules. Here we report the ultrahigh resolution imaging of water molecules on a NaCl film by NC-AFM, which enables us to determine the topology of hydrogen-bonding network in unprecedented details. Comparison with the theoretical simulations reveals that the sharp features in the AFM images result from the relaxation of the tip apex mainly due to the electrostatic force between the tip and the water molecules. Our results shed new light on the underlying mechanism of the ultrahigh imaging with NC-AFM and highlight the importance of electrostatics in the imaging of polar molecules such as water. [Preview Abstract] |
Monday, March 14, 2016 10:00AM - 10:12AM |
A46.00009: Tip relaxation in atomic force microscopy imaging simulations to resolve intermolecular bonds Alex Lee, Yuki Sakai, Jim Chelikowsky Experimental noncontact atomic force microscopy (AFM) studies have reported distinct lines in regions with no electron density for a variety of systems. The appearance of these lines is unexpected because Pauli repulsion is thought to be the dominant factor in the AFM imaging mechanism. These lines have been proposed to represent intermolecular bonding. Recent theoretical studies have shown that accounting for tip probe relaxation can sharpen images and highlight features that make simulations more comparable to experiment. We will apply a similar tip relaxation scheme to our computational method--which uses an \emph{ab initio} real-space pseudopotential formalism with frozen density embedding theory added--to the study of dibenzo[a,h]thianthrene and an 8-hydroxyquinoline dimer to develop our interpretation of imaged intermolecular bonds. [Preview Abstract] |
Monday, March 14, 2016 10:12AM - 10:24AM |
A46.00010: First-principles AFM image simulation with frozen density embedding theory Yuki Sakai, Alex J. Lee, James R. Chelikowsky We present efficient first-principles method of non-contact atomic force microscopy (nc-AFM). Ordinary nc-AFM simulations based on density functional theory (DFT) require exhaustive computational cost because it involves thousands of total energy calculations. Regarding the sample as a fixed external potential can reduce the computational cost, and we adopt frozen density embedding theory (FDET) for this purpose. Simulated nc-AFM images with FDET using a carbon monoxide tip well reproduces the full DFT images of benzene, pentacene, and graphene, although optimized tip-sample distances and interaction energies in FDET are underestimated and overestimated, respectively. The FDET-based simulation method is promising for AFM image simulation of surfaces and two-dimensional materials. [Preview Abstract] |
Monday, March 14, 2016 10:24AM - 10:36AM |
A46.00011: Isotope-Resolved and Charge-Sensitive Force Imaging Using Scanned Single Molecules Yan Sun, Dominik Rastawicki, Yang Liu, Warren Mar, Hari Manoharan, Anna Miglio, Sorin Melinte, Jean-Christophe Charlier, Gian-Marco Rignanese, Lianhua He, Fang Liu, Aihui Zhou Originally conceived as surface imaging instruments, the scanning tunnelling microscope (STM) and the atomic force microscope (AFM) were recently used to probe molecular chemical bonds with exquisite sensitivity. Remarkably, molecule-functionalized scanning tips can also provide direct access to the inelastic electron tunneling spectrum (IETS) of the terminal molecule. Here we report atomic manipulation experiments addressing carbon monoxide (CO) isotopes at low temperatures. The unique and quantifiable dependence of the CO vibrational modes offers insight into tip-controlled force and charge sensing of surface adsorbates, subsurface defects, and quantum nanostructures. The specific behavior of the monitored vibrational modes originates from the interplay of interaction forces between the top electrode---a scanned tip functionalized with a single molecule---and the atomic scale force field surrounding the target atomically-assembled nanostructure. We also present density functional theory (DFT) computations that have been performed in order to scrutinize and visualize the vibrational spectroscopic fingerprints and local force fields. [Preview Abstract] |
Monday, March 14, 2016 10:36AM - 10:48AM |
A46.00012: A cryogen-free variable temperature scanning tunneling microscope capable for inelastic electron tunneling spectroscopy Shuai Zhang, Di Huang, Shiwei Wu While low temperature scanning tunneling microscope (STM) has become an indispensable research tool in surface science, its versatility is yet limited by the shortage or high cost of liquid helium. The makeshifts include the use of alternative cryogen (such as liquid nitrogen) at higher temperature or the development of helium liquefier system usually at departmental or campus wide. The ultimate solution would be the direct integration of a cryogen-free cryocooler based on GM or pulse tube closed cycle in the STM itself. However, the nasty mechanical vibration at low frequency intrinsic to cryocoolers has set the biggest obstacle because of the known challenges in vibration isolation required to high performance of STM. In this talk, we will present the design and performance of our home-built cryogen-free variable temperature STM at Fudan University. This system can obtain atomically sharp STM images and high resolution dI/dV spectra comparable to state-of-the-art low temperature STMs, but with no limitation on running hours. Moreover, we demonstrated the inelastic tunneling spectroscopy (STM-IETS) on a single CO molecule with a cryogen-free STM for the first time. [Preview Abstract] |
Monday, March 14, 2016 10:48AM - 11:00AM |
A46.00013: Cryogen free scanning probe microscope: the solution for atomic scale surface science below 10 Kelvin without liquid helium Byoung Choi, Miguel Venegas We present a cryogen free low temperature scanning probe microscope (LT-SPM) working at 9K on both tip and sample. The performance of the microscope was validated in various conditions such as noisy environment and modulated temperature as well as the long time elapsed measurements. Building on the stability and consistency of the closed cycle refrigerator, time extended measurements are available with this state-of-the-art LT-SPM. Studies can now be performed without interrupting the critical moment of the tip on the surface while refilling the conventional liquid cryogen tank. We will present the time evolution of the dopant induced topographic and spectroscopic properties of some topological insulators such as Bi2Se3 and Bi2Te3. The compact and rigid design of the microscope also allows this instrument to work as a practical variable temperature microscope without the hassle of liquid cryogen consumption. We will present temperature dependent STM/STS results on a TiSe2 surface at the temperature between 10K and 350K. Finally, we will discuss how the cryogen free LT-SPM will make the study of the atomic scale phenomenon at low temperature both economical and easy, opening promising new capabilities to surface scientists and researchers in nanotechnology. [Preview Abstract] |
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