Journal articles on the topic 'Tip-sample-substrate interaction'
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1
Jaafar, Miriam, Oscar Iglesias-Freire, Luis Serrano-Ramón, Manuel Ricardo Ibarra, Jose Maria de Teresa, and Agustina Asenjo. "Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy–magnetic force microscopy combination." Beilstein Journal of Nanotechnology 2 (September 7, 2011): 552–60. http://dx.doi.org/10.3762/bjnano.2.59.
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The most outstanding feature of scanning force microscopy (SFM) is its capability to detect various different short and long range interactions. In particular, magnetic force microscopy (MFM) is used to characterize the domain configuration in ferromagnetic materials such as thin films grown by physical techniques or ferromagnetic nanostructures. It is a usual procedure to separate the topography and the magnetic signal by scanning at a lift distance of 25–50 nm such that the long range tip–sample interactions dominate. Nowadays, MFM is becoming a valuable technique to detect weak magnetic fields arising from low dimensional complex systems such as organic nanomagnets, superparamagnetic nanoparticles, carbon-based materials, etc. In all these cases, the magnetic nanocomponents and the substrate supporting them present quite different electronic behavior, i.e., they exhibit large surface potential differences causing heterogeneous electrostatic interaction between the tip and the sample that could be interpreted as a magnetic interaction. To distinguish clearly the origin of the tip–sample forces we propose to use a combination of Kelvin probe force microscopy (KPFM) and MFM. The KPFM technique allows us to compensate in real time the electrostatic forces between the tip and the sample by minimizing the electrostatic contribution to the frequency shift signal. This is a great challenge in samples with low magnetic moment. In this work we studied an array of Co nanostructures that exhibit high electrostatic interaction with the MFM tip. Thanks to the use of the KPFM/MFM system we were able to separate the electric and magnetic interactions between the tip and the sample.
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Chan, Nicholas, Carrie Lin, Tevis Jacobs, Robert W. Carpick, and Philip Egberts. "Quantitative determination of the interaction potential between two surfaces using frequency-modulated atomic force microscopy." Beilstein Journal of Nanotechnology 11 (May 6, 2020): 729–39. http://dx.doi.org/10.3762/bjnano.11.60.
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The interaction potential between two surfaces determines the adhesive and repulsive forces between them. It also determines interfacial properties, such as adhesion and friction, and is a key input into mechanics models and atomistic simulations of contacts. We have developed a novel methodology to experimentally determine interaction potential parameters, given a particular potential form, using frequency-modulated atomic force microscopy (AFM). Furthermore, this technique can be extended to the experimental verification of potential forms for any given material pair. Specifically, interaction forces are determined between an AFM tip apex and a nominally flat substrate using dynamic force spectroscopy measurements in an ultrahigh vacuum (UHV) environment. The tip geometry, which is initially unknown and potentially irregularly shaped, is determined using transmission electron microscopy (TEM) imaging. It is then used to generate theoretical interaction force–displacement relations, which are then compared to experimental results. The method is demonstrated here using a silicon AFM probe with its native oxide and a diamond sample. Assuming the 6-12 Lennard-Jones potential form, best-fit values for the work of adhesion (W adh) and range of adhesion (z 0) parameters were determined to be 80 ± 20 mJ/m2 and 0.6 ± 0.2 nm, respectively. Furthermore, the shape of the experimentally extracted force curves was shown to deviate from that calculated using the 6-12 Lennard-Jones potential, having weaker attraction at larger tip–sample separation distances and weaker repulsion at smaller tip–sample separation distances. This methodology represents the first experimental technique in which material interaction potential parameters were verified over a range of tip–sample separation distances for a tip apex of arbitrary geometry.
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Gilliss, Shelley R., Jeffrey K. Fairer, N. Ravishankar, Mark G. Schwabel, and C. Barry Carter. "Microanalysis of AFM Tips Coated with Cerium Oxide." Microscopy and Microanalysis 7, S2 (August 2001): 1236–37. http://dx.doi.org/10.1017/s1431927600032256.
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Cerium oxide is widely used for chemomechanical polishing (CMP) of silicate glasses. Uses include finishing of optical elements and planarizing dielectrics in the semiconductor industry. This study is designed to investigate the fundamentals of the cerium oxide/silica CMP process by measuring the interaction force between silicate glasses and cerium oxide. Surface forces involved in the polishing of glass by a cerium oxide abrasive can be studied in a controlled manner by measuring sample-tip interactions between a glass substrate and a cerium oxide tip in an atomic force microscope (AFM). Commercially available AFM tips have been coated with thin, uniform films of cerium oxide. By using a square pyramid tip as a template for the shape of the cerium oxide film, challenges related to irregular or blunt tip shape can be overcome. However, complete characterization of structure, shape and chemical composition is required before useful information can be obtained using the AFM.
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Yamanishi, Junsuke, Hidemasa Yamane, Yoshitaka Naitoh, Yan Jun Li, and Yasuhiro Sugawara. "Local spectroscopic imaging of a single quantum dot in photoinduced force microscopy." Applied Physics Letters 120, no. 16 (April 18, 2022): 161601. http://dx.doi.org/10.1063/5.0088634.
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Analysis of environmentally sensitive materials is essential for developing and optimizing nanostructured photochemical materials and devices. Photoinduced force microscopy (PiFM) is a promising local spectroscopic technique to visualize nanoscale local optical responses by measuring the optical forces between the scanning tip and sample. In this study, we examined isolated single quantum dots (QDs) with ligands on a gold substrate via PiFM under ultra-high vacuum to characterize the QD adsorption state on the basis of the optical force. The strong self-consistent optical interaction through the tip-substrate plasmonic gap induced by laser light modulates the PiFM image depending on QD crystal existence in the gap. This observation clarified the QD absorption situation on the substrate, and the crystal position in the QDs was determined even though the ligand walls covered the crystal. This insight concerning force spectroscopy can aid further research on the photochemistry of nanostructured materials and molecular spectroscopy.
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Keivanidis, Panagiotis E., Andrea di Donato, Davide Mencarelli, Alessandro Esposito, Tengling Ye, Guglielmo Lanzani, Giuseppe Venanzoni, Tiziana Pietrangelo, Antonio Morini, and Marco Farina. "Determining the Efficiency of Fast Ultrahigh-density Writing of Low-Conductivity Patterns on Semiconducting Polymers." MRS Proceedings 1729 (2015): 125–30. http://dx.doi.org/10.1557/opl.2015.81.
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ABSTRACTWe present a nano-patterning process for semiconducting polymeric composites that could potentially be utilized for the development of polymer-based data storage devices. Nano-patterning (writing) operates on the basis of the mechanical interaction between the electrically unbiased tip of an atomic force microscope and the surface of polymeric composite films. Via friction forces, the tip/sample interaction produces a local increase of molecular disorder in the polymer matrix, inducing a localized lowering in the conductivity of the organic semiconductor. Herein we suggest a figure of merit for quantifying the efficiency of pattern formation and we address the dependence of the writing process on the thermal annealing temperature of the composite film. Control experiments on composite films deposited on substrates with different roughness suggest that the writing effect is invariant to the roughness of the substrate. The potential storage density of the writing process depends on the tip curvature.
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Kheirodin, Mohsen, Hossein Nejat Pishkenari, Ali Moosavi, and Ali Meghdari. "Study of Biomolecules Imaging Using Molecular Dynamics Simulations." Nano 10, no. 07 (October 2015): 1550096. http://dx.doi.org/10.1142/s1793292015500964.
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The process of imaging a biomolecule by atomic force microscope (AFM) is modeled using molecular dynamics (MD) simulations. Since the large normal force exerted by the tip on the biosample in contact and tapping modes may damage the sample structure and produce irreversible deformation, the noncontact mode of AFM (NC-AFM) is employed as the operating mode. The biosample is scanned using a carbon nanotube (CNT) as the AFM probe. CNTs because of their small diameter, high aspect ratio and high mechanical resistance attract many attentions for imaging purposes. The tip–sample interaction is simulated by the MD method. The protein, which has been considered as the biomolecule, is ubiquitin and a graphene sheet is used as the substrate. The effects of CNT's geometric parameters such as the CNT height, the diameter, the tilt angle, the flexibility and the number of layers on the image quality have been evaluated.
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CZAJKA, R., A. KASUYA, A. WAWRO, N. HORIGUCHI, and Y. NISHINA. "FORMATION AND MODIFICATION OF MESOSCOPIC STRUCTURES ON GRAPHITE (HOPG) AND SILICON SURFACES BY MEANS OF SCANNING TUNNELING MICROSCOPY." Surface Review and Letters 03, no. 01 (February 1996): 961–67. http://dx.doi.org/10.1142/s0218625x96001728.
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This paper presents results of our experimental investigations of the adsorption and interaction of microclusters on some crystalline surfaces to form regular arrangements. Microclusters were produced and deposited up to a monolayer coverage on the c-plane of graphite (HOPG) or Si(111) substrates by thermal evaporation, laser ablation, or deposition from STM tip. A rectangular lattice arrangement of Se n(n=5–8) ring cluster has been fabricated for the first time on the HOPG. Also, arrays of Au clusters with a well-controlled diameter, desired periodicity, and size have been obtained by applying a sequence of voltage pulses between the STM tip and the substrate. A variety of carbon clusters have been produced by laser modification of C 60 fullerenes, and observed by means of scanning tunneling microscope (STM). Finally, various nanometer-scale structures have been modified by applying different bias voltages (between tip probe and sample) or induced by thermal treatment.
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Leite, F. L., E. C. Ziemath, O. N. Oliveira Jr., and P. S. P. Herrmann. "Adhesion Forces for Mica and Silicon Oxide Surfaces Studied by Atomic Force Spectroscopy (AFS)." Microscopy and Microanalysis 11, S03 (December 2005): 130–33. http://dx.doi.org/10.1017/s1431927605051068.
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The possibility of analyzing surfaces at the nanoscale provided by atomic force microscopy [1] (AFM) has been explored for various materials, including polymers [2], biological materials [3] and clays [4]. Further uses of AFMs involved nanomanipulation [5] and measurements of interaction forces, where the latter has been referred to as atomic force spectroscopy (AFS) [6]. Measurements of surface-surface interactions at the nanoscale are important because many materials have their properties changed at this range [7]. For samples in air, the interactions with the tip are a superimposition of van der Waals, electrostatic and capillary forces. A number of surface features can now be monitored with AFS, such as adsorption processes and contamination from the environment. Many implications exist for soil sciences and other areas, because quantitative knowledge of particle adhesion is vital for understanding technological processes, including particle aggregation in mineral processing, quality of ceramics and adhesives. In this paper, we employ AFS to measure adhesion (pull-off force) between the AFM tip and two types of substrate. Adhesion maps are used to illustrate sample regions that had been contaminated with organic compounds.
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Meyer, G., and K. H. Rieder. "Lateral Manipulation of Single Adsorbates and Substrate Atoms With the Scanning Tunneling Microscope." MRS Bulletin 23, no. 1 (January 1998): 28–32. http://dx.doi.org/10.1557/s0883769400031432.
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The stability and precision of modern scanning-tunneling-microscope (STM) systems allow positioning of the tip on a subnanometer scale. This advancement has stimulated diverse efforts on surface modifications in the nanometer and even atomic range, as recently reviewed by Avouris. The lateral movement of individual adatoms and molecules in a controlled manner on solid surfaces and the construction of structures on a nanoscale were first demonstrated by Eigler and collaborators at 4 K. The reason for operating the STM at low temperatures (apart from increased stability and sensitivity of the STM setup itself) is the necessity to freeze the motion of single adsorbates, which are very often mobile at ambient temperatures. By selecting strongly bonded adsorbate/substrate combinations and large molecules, it was possible to extend the lateral manipulation technique even to room temperature. In the case of large molecules, not only their translational motion but also internal flexure of the molecule during the positioning process must be considered. In general, different physical and chemical interaction mechanisms between tip and sample can be exploited for atomic-scale manipulation. We will concentrate in the following on lateral manipulation where solely the forces that act on the adsorbate because of the proximity of the tip are used. This means that long-range van der Waals and short-range chemical forces can be used to move atoms or molecules along the surface. No bias voltage or tunneling current is necessary. Apart from this technique, additional advances using the effects caused by the electric field generated by the bias voltage between tip and sample and by the current flowing through the gap region can be used for atomic or molecular modification.
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Cruz Valeriano, Edgar, José Juan Gervacio Arciniega, Christian Iván Enriquez Flores, Susana Meraz Dávila, Joel Moreno Palmerin, Martín Adelaido Hernández Landaverde, Yuri Lizbeth Chipatecua Godoy, Aime Margarita Gutiérrez Peralta, Rafael Ramírez Bon, and José Martín Yañez Limón. "Stochastic excitation for high-resolution atomic force acoustic microscopy imaging: a system theory approach." Beilstein Journal of Nanotechnology 11 (May 4, 2020): 703–16. http://dx.doi.org/10.3762/bjnano.11.58.
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In this work, a high-resolution atomic force acoustic microscopy imaging technique is developed in order to obtain the local indentation modulus at the nanoscale level. The technique uses a model that gives a qualitative relationship between a set of contact resonance frequencies and the indentation modulus. It is based on white-noise excitation of the tip–sample interaction and uses system theory for the extraction of the resonance modes. During conventional scanning, for each pixel, the tip–sample interaction is excited with a white-noise signal. Then, a fast Fourier transform is applied to the deflection signal that comes from the photodiodes of the atomic force microscopy (AFM) equipment. This approach allows for the measurement of several vibrational modes in a single step with high frequency resolution, with less computational cost and at a faster speed than other similar techniques. This technique is referred to as stochastic atomic force acoustic microscopy (S-AFAM), and the frequency shifts of the free resonance frequencies of an AFM cantilever are used to determine the mechanical properties of a material. S-AFAM is implemented and compared with a conventional technique (resonance tracking-atomic force acoustic microscopy, RT-AFAM). A sample of a graphite film on a glass substrate is analyzed. S-AFAM can be implemented in any AFM system due to its reduced instrumentation requirements compared to conventional techniques.
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Narlikar, A. V., S. B. Samanta, P. K. Dutta, L. S. Grigoryan, and A. K. Majumdar. "High-resolution direct observation of the carbon-cage structure of C60 buckyballs." Journal of Applied Crystallography 25, no. 5 (October 1, 1992): 657–60. http://dx.doi.org/10.1107/s0021889892007490.
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In C60 films containing higher fullerene derivatives and having electrically conducting islands, it has been possible for the first time to observe, using high resolution scanning tunnelling electron microscopy (STM), the individual carbon cage of C60 buckyballs forming a f.c.c. lattice on a silver-coated glass substrate. The observed images of the molecule are surprisingly distinct and not smeared out, indicating their ambient-temperature reorientational motion to be pinned. The possible causes of the freezing are: (i) the presence of higher fullerene derivatives; (ii) changes in the electronic structure of the films due to interaction and proximity of Ag atoms; and (iii) the pinning of the molecules by the presence of large electric field gradients between the STM tip and the sample surface, a factor which, in addition, is considered responsible for the distortion observed in the buckyball images.
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Khalsa, Partap S., Robert H. Lamotte, and Peter Grigg. "Tensile and Compressive Responses of Nociceptors in Rat Hairy Skin." Journal of Neurophysiology 78, no. 1 (July 1, 1997): 492–505. http://dx.doi.org/10.1152/jn.1997.78.1.492.
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Khalsa, Partap S., Robert H. LaMotte, and Peter Grigg. Tensive and compressive responses of nociceptors in rat hairy skin. J. Neurophysiol. 78: 492–505, 1997. Mechanically sensitive nociceptor afferents were studied in a preparation of isolated skin from rat leg. Each neuron was studied while the skin was subjected to tensile and compressive loading. The experiment was designed to create highly uniform states of stress in both tension and compression. Tensile loads were applied by pulling on the edges of the sample. Applied loads were used to determine the tensile stresses. Surface displacements were used to determine tensile strains. Compressive loads were applied by indenting the surface of the skin with flat indenter tips applied under force control. The skin was supported by a flat, hard substrate. Compressive stresses were determined from the applied loads and tip geometry. Compressive strains were determined from skin thickness and tip excursions. All nociceptors were activated by both tensile and compressive loading. There was no interaction between the responses to compressive and tensile stimuli (i.e., the responses were simply additive). Responses of nociceptors were better related to tensile and compressive stresses than to strains. Nociceptors responded better to tensile loading than to compressive loading. Response thresholds were lower and sensitivities were higher for tensile stress than for compressive stress. The response to compression was better related to compressive stress than to other stimulus parameters (i.e., load/circumference or simply load). Indentations of intact skin over a soft substrate such as muscle would be expected to cause widespread activation of nociceptors because of tensile stresses.
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Fei, L. "Distortion in lattice-resolution scanned-probe microscope images." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 522–23. http://dx.doi.org/10.1017/s0424820100148447.
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Scanned probe microscopes (SPM) have been widely used for studying the structure of a variety material surfaces and thin films. Interpretation of SPM images, however, remains a debatable subject at best. Unlike electron microscopes (EMs) where diffraction patterns and images regularly provide data on lattice spacings and angles within 1-2% and ∽1° accuracy, our experience indicates that lattice distances and angles in raw SPM images can be off by as much as 10% and ∽6°, respectively. Because SPM images can be affected by processes like the coupling between fast and slow scan direction, hysteresis of piezoelectric scanner, thermal drift, anisotropic tip and sample interaction, etc., the causes for such a large discrepancy maybe complex even though manufacturers suggest that the correction can be done through only instrument calibration.We show here that scanning repulsive force microscope (SFM or AFM) images of freshly cleaved mica, a substrate material used for thin film studies as well as for SFM instrument calibration, are distorted compared with the lattice structure expected for mica.
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Chen, Y. H., X. J. Li, X. F. Zhou, Jia Lin Sun, W. H. Huang, and J. Hu. "Determining the Radial Modulus of DNA Measured by VPSFM." Key Engineering Materials 295-296 (October 2005): 83–88. http://dx.doi.org/10.4028/www.scientific.net/kem.295-296.83.
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Mechanical properties of DNA, for example the elastic modulus, are of vital importance for its biological function. Previously, the modulus is mainly obtained by bending, stretching and twisting DNA using various techniques and tools. By applying vibrating mode scanning polarization force microscopy (VPSFM), deformations of DNA under ultra-small indentation forces can be measured and so the radial modulus can be computed. In this paper, modeling of the VPSFM measuring system is presented. The system is modeled as a spring-mass-damper oscillator under various force fields, such as van der Waals force, attractive electrical force and repulsive interactions between the tip and sample. The electrical polarization force is described by using uniformly charged line model and the DNA is considered to be a simple elastic rod. By numerically integrating the equation of tip motion, the contact force and the radial modulus of DNA under different deformation can be calculated. We found that in measuring radial modulus of DNA, the existence of substrate cannot be neglected, especially when the relative large deformation is reached.
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Montazeri, Mohadeseh, Amir Hashemi, Behzad Houshmand, and Shahab Faghihi. "The Effect of Bio-Conditioning of Titanium Implants for Enhancing Osteogenic Activity." Journal of Oral Implantology 45, no. 3 (June 1, 2019): 187–95. http://dx.doi.org/10.1563/aaid-joi-d-18-00020.
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Early and effective integration of titanium-based materials into bone tissue is of vital importance for long-term stability of implants. Surface modification is commonly used to enhance cell-substrate interactions for improving cell adhesion, proliferation, and activity. Here, the surface of titanium substrates and commercial implants were coated with blood (TiB), fetal bovine serum (TiF), and phosphate-buffered saline (TiP) solution using a spin coating process. Surface roughness and wettability of samples were measured using contact angle measurements and atomic force microscopy. The samples were then exposed to human osteoblast-like MG63 cells in order to evaluate adhesion, growth, differentiation, and morphology on the surface of modified samples. Untreated titanium disks were used as controls. The lowest roughness and wettability values were found in unmodified titanium samples followed by TiP, TiF, and TiB. The percentage of cellular attachment and proliferation for each sample was measured using an MTT (3-[4,5-dimethylthiazol-2yl] 2,5diphenyl-2H-tetrazoliumbromide) assay. Cell adhesion and proliferation were most improved on TiB followed closely by TiF. The results of this study revealed an increased expression of the osteogenic marker protein alkaline phosphatase on TiB and the coated commercial titanium implants. These results suggested that precoating titanium samples with blood may improve cellular response by successfully mimicking a physiological environment that could be beneficial for clinical implant procedures.
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Falvo, M. R., G. Clary, A. Helser, S. Paulson, R. M. Taylor, V. Chi, F. P. Brooks, S. Washburn, and R. Superfine. "Nanomanipulation Experiments Exploring Frictional and Mechanical Properties of Carbon Nanotubes." Microscopy and Microanalysis 4, no. 5 (October 1998): 504–12. http://dx.doi.org/10.1017/s1431927698980485.
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In many cases in experimental science, the instrument interface becomes a limiting factor in the efficacy of carrying out unusual experiments or prevents the complete understanding of the acquired data. We have developed an advanced interface for scanning probe microscopy (SPM) that allows intuitive rendering of data sets and natural instrument control, all in real time. The interface, called the nanoManipulator, combines a high-performance graphics engine for real-time data rendering with a haptic interface that places the human operator directly into the feedback loop that controls surface manipulations. Using a hand-held stylus, the operator moves the stylus laterally, directing the movement of the SPM tip across the sample. The haptic interface enables the user to “feel” the surface by forcing the stylus to move up and down in response to the surface topography. In this way the user understands the immediate location of the tip on the sample and can quickly and precisely maneuver nanometer-scale objects. We have applied this interface to studies of the mechanical properties of nanotubes and to substrate-nanotube interactions. The mechanical properties of carbon nanotubes have been demonstrated to be extraordinary. They have an elastic modulus rivaling that of the stiffest material known, diamond, while maintaining a remarkable resistance to fracture. We have used atomic-force microscopy (AFM) to manipulate the nanotubes through a series of configuration that reveal buckling behavior and high-strain resilience. Nanotubes also serve as test objects for nanometer-scale contact mechanics. We have found that nanotubes will roll under certain conditions. This has been determined through changes in the images and through the acquisition of lateral force during manipulation. The lateral force data show periodic stick-slip behavior with a periodicity matching the perimeter of the nanotube.
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Zhou, Huimin, Yingchun Jiang, Christopher M. Dmuchowski, Changhong Ke, and Jia Deng. "Electric-Field-Assisted Contact Mode AFM-Based Nanolithography with Low Stiffness Conductive Probes." Journal of Micro and Nano-Manufacturing, April 9, 2022. http://dx.doi.org/10.1115/1.4054316.
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Abstract Electric-field-assisted atomic force microscope (E-AFM) nanolithography is a novel polymer-patterning technique that has diverse applications. E-AFM uses a biased AFM tip with conductive coatings to make patterns with little probe-sample interaction, which thereby avoids the tip wear that is a major issue for contact-mode AFM-based lithography, which usually requires a high probe-sample contact force to fabricate nanopatterns; however, the relatively large tip radius and large tip-sample separation limit its capacity to fabricate high-resolution nanopatterns. In this paper, we developed a contact mode E-AFM nanolithography approach to achieve high-resolution nanolithography of poly (methyl methacrylate) (PMMA) using a conductive AFM probe with a low stiffness (~0.16 N/m). The nanolithography process generates features by biasing the AFM probe across a thin polymer film on a metal substrate. A small constant force (0.5-1 nN) applied on the AFM tip helps engage the tip-film contact, which enhances nanomachining resolution. This E-AFM nanolithography approach enables high-resolution nanopatterning with feature width down to ~16 nm, which is less than one half of the nominal tip radius of the employed conductive AFM probes.
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Sarih, Norfatirah Muhamad, David Romero-Perez, Behnam Bastani, Monrawat Rauytanapanit, Cedric Boisdon, Thanit Praneenararat, Hairul Anuar Tajuddin, Zanariah Abdullah, Abraham K. Badu-Tawiah, and Simon Maher. "Accelerated nucleophilic substitution reactions of dansyl chloride with aniline under ambient conditions via dual-tip reactive paper spray." Scientific Reports 10, no. 1 (December 2020). http://dx.doi.org/10.1038/s41598-020-78133-4.
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AbstractPaper spray ionization (PSI) mass spectrometry (MS) is an emerging tool for ambient reaction monitoring via microdroplet reaction acceleration. PSI-MS was used to accelerate and monitor the time course of the reaction of dansyl chloride with aniline, in acetonitrile, to produce dansyl aniline. Three distinct PSI arrangements were explored in this study representing alternative approaches for sample loading and interaction; conventional single tip as well as two novel setups, a dual-tip and a co-axial arrangement were designed so as to limit any on-paper interaction between reagents. The effect on product abundance was investigated using these different paper configurations as it relates to the time course and distance of microdroplet travel. It was observed that product yield increases at a given distance and then decreases thereafter for all PSI configurations. The fluorescent property of the product (dansyl aniline) was used to visually inspect the reaction progress on the paper substrate during the spraying process. Amongst the variety of sample loading methods the novel dual-tip arrangement showed an increased product yield and microdroplet density, whilst avoiding any on-paper interaction between the reagents.
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Bozhko, Sergey I., Killian Walshe, and Igor V. Shvets. "Control of binding of C60 molecules to the substrate by Coulomb blockade." Scientific Reports 9, no. 1 (November 5, 2019). http://dx.doi.org/10.1038/s41598-019-52544-4.
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Abstract We report on a transition in a monolayer of C60 molecules deposited on a WO2/W(110) substrate. The transition from a static state, where the molecules are rigidly bound to the surface by a coordination bond, to a state where the molecules are loosely bound to the surface by van der Waals force and rotate continuously, has been studied using scanning tunnelling microscopy (STM). The separation between the molecules and the surface increases by 1.2 Å across the transition. The transition from the static state into the rotating state takes place at 259 K. The energy of the spinning state with respect to the lowest energy state, having a single coordinated bond, can be obtained from the statistics of the molecules switching. The binding energy of the molecule in the spinning state can be easily altered by changing the polarity of the bias voltage applied between the STM tip and the surface. The binding energy decreases by 80 meV when the bias polarity of the sample changes from positive to negative with respect to the tip. The results are consistent with the Coulomb blockade model: when electrons travel from the surface to the C60 molecule, and then to the tip; charge accumulates on the molecule due to the Coulomb blockade. This increases the electrostatic interaction between the molecule’s charge and a corresponding image charge generated on the metallic surface.
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Karacharov, Anton A., and Maxim N. Likhatski. "A Comparative Study of Features of Sorption of N-Buthylxanthate and Dibuthyldixanthogen Onto Metallic Supports and Rutile Using in situ Atomic Force Spectroscopy." Journal of Siberian Federal University. Chemistry, September 2019, 336–46. http://dx.doi.org/10.17516/1998-2836-0131.
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An interaction of potassium buthylxanthate and of dibuthyldixanthogen with metallic Ti, stainless steel and α-TiO2 surfaces was studied. Contact angle measurements by sessile drop technique showed that the treatment of initial substrate surfaces with potassium buthylxanthate aqueous solution or with dibuthyldixanthogen emulsion render them more hydrophobic. Using in situ atomic force spectroscopy, the sorption of surface active substances was shown to give rise to an increase in both adhesive force magnitude and the range within it acts at the approach of cantilever tip to the surface of both hydrophobic and hydrophilic samples. The maximum of both adhesive force and their range, up to 150 nm, took place in case of retract of cantilever tip from sample surface. Force curves are steeper, which related with the formation of nanobubbles on the surfaces of samples under study arising the longrange hydrophobic force of capillary origin. Dibuthyldixanthogen exhibited highly-active reagent properties inducing the formation of nanoscale gas structures on both hydrophobic and, in less extent, hydrophilic surfaces
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Hasan, Md Mahamudal, Toyoko Arai, and Masahiko TOMITORI. "Mechanical energy dissipation of an oscillating cantilever close to a conductive substrate partly covered with thin mica films evaluated by frequency modulation atomic force microscopy." Japanese Journal of Applied Physics, April 27, 2022. http://dx.doi.org/10.35848/1347-4065/ac6b02.
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Abstract Mechanical energy stored in an oscillating cantilever in frequency modulation atomic force microscopy (FM-AFM) was dissipated through nonconservative interactions between a sample and a tip on the cantilever. The energy dissipation (Ddis) was measured using FM-AFM with a metal-coated tip for a metal-coated Si substrate partly covered with thin mica films. At tip–sample separations where electrostatic force was dominant under a bias voltage, Joule heat was generated owing to the tip oscillation, responsible for Ddis. From analysis of Ddis and the frequency shift of the cantilever, electric resistance responsible for the Joule heat was estimated to be of the order of GΩ. The great values of the resistance were discussed in the terms of surface scattering of charges moved by the oscillating tip and the dielectric energy loss in the mica films. Measurement of the energy dissipation exhibited potential to probe the local surface electronic properties in non-contact.
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Kayal, Arijit, Prahalad Barman, Prasad V. Sarma, Manikoth Shaijumon, Rajeev Kini, and Joy Mitra. "Symmetric domain segmentation in WS2 flakes: correlating spatially resolved photoluminescence, conductance with valley polarization." Nanotechnology, August 30, 2022. http://dx.doi.org/10.1088/1361-6528/ac8d9d.
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Abstract The incidence of intra-flake heterogeneity of spectroscopic and electrical properties in chemical vapour deposited (CVD) WS2 flakes is explored in a multi-physics investigation, via spatially resolved spectroscopic maps correlated with electrical, electronic and mechanical properties. The investigation demonstrates that the three-fold symmetric segregation of spectroscopic response, in topographically uniform WS2 flakes are accompanied by commensurate segmentation of electronic properties e.g. local carrier density and the differences in the mechanics of tip-sample interactions, evidenced via scanning probe microscopy phase maps. Overall, the differences are understood to originate from point defects, namely sulphur vacancies within the flake along with a dominant role played by the substrate. While evolution of the multi-physics maps upon sulphur annealing elucidates the role played by S-vacancy, substrate-induced effects are investigated by contrasting data from WS2 flake on Si and Au surfaces. Local charge depletion induced by the nature of the sample-substrate junction in case of WS2 on Au is seen to invert the electrical response with comprehensible effects on their spectroscopic properties. Finally, the role of these optoelectronic properties in preserving valley polarization, affecting valleytronic applications, in WS2 flakes is investigated via circular polarisation discriminated photoluminescence experiments. The study provides a thorough understanding of spatial heterogeneity in optoelectronic properties of WS2 and other two-dimensional transition metal chalcogenides, which are critical for device fabrication and potential applications.
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Campbell, Paul, and George Walmsley. "Pseudo-wetting Behaviour of Nanostructures Induced by STM." MRS Proceedings 1059 (2007). http://dx.doi.org/10.1557/proc-1059-kk10-38.
Full textAbstract:
ABSTRACTThe behavior of nano-scale liquid metal droplets has recently received renewed research interest following the exciting new observations of Sutter and Sutter [1]. In the present paper, we consider whether similar conditions can be generated for observing liquid metal droplet phenomena in a scanning probe architecture. Strong interactions between tip and sample in tunnelling microscopies can be deliberately invoked by lowering the tunnel gap impedance. Indeed, nanoscale features may be created this may, often exhibiting temporal stability suggestive of applications for ultra high density data storage. Alternatively, unstable features may form, and their decay characteristics can be related to local dynamics and kinetics. In real liquids, one such evolutionary mode involves the phenomenon of wetting, and the formation of thin precursor films. Here, it is demonstrated that a similar process may occur for the decay of a nanoscale mound of [presumed] Au atoms onto an Au(111) substrate. The mound is thought to be created by a ‘jump-to-contact’ process when the gap impedance, Zg, is deliberately lowered by reducing the tip-surface displacement. Resultant features have a diameter of circa 30nm, and heights of up to l0nm. They appear stable when scanned repeatedly at gap impedances higher than 10MΩ, however if Zg is lowered below 500kΩ, then morphology can alter dynamically, and a thin layer of material, only two atomic widths thick, is seen to emanate from the periphery. Relaxation in the nanostructure is observed. Interestingly, the observations agree qualitatively with wetting phenomena observed on microscale droplets of involatile liquids on solid surfaces. Favourable comparisons may also be drawn in the light of recent results using molecular-dynamics simulations and Monte-Carlo methods.