Dynamic atomic force microscopy methods

Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.

Micromachining a miniaturized capillary electrophoresis-based chemical analysis system on a chip

http://myweb.rz.uni-augsburg.de/~eckern/WEH-287/ABSTRACTS/ruitenbeek.pdf

Quantum properties of atomic-sized conductors

A few years after the invention of the scanning tunneling microscope (STM), the atomic force microscope (AFM) was developed Instead of measuring tunneling current, a new physical quantity could be investigated with atomic-scale resolution: the force between a small tip and a chosen sample surface This paper reviews progress and recent results obtained with AFM and other closely related techniques in the field of nanotribology, and attempts to point out many of the unresolved questions that remain The goal of this paper is to demonstrate that AFM is capable of producing atomic-scale knowledge As such, the authors will focus upon some of the contributions of the AFM to nanotribology They will almost exclusively discuss results that shed light on the actual atomic and molecular processes taking place, as opposed to the more applied investigations of microscale properties which are also carried out with AFM They will accompany this discussion by mentioning related theoretical efforts and simulations, although their main emphasis will be upon experimental results and the techniques used to obtain them, as well as suggested future directions In many ways, AFM techniques for quantitative, fundamental nanotribology are only in a nascent stage; certain key issues such as force calibration,more » tip characterization, and the effects of the experimental environment, are not fully resolved or standardized The authors thus begin with a critical discussion of the relevant technical aspects with using AFM for nanotribology 289 refs« less

/pdf/scratching-the-surface-fundamental-investigations-of-4kjq5s243s.pdf

Scratching the Surface: Fundamental Investigations of Tribology with Atomic Force Microscopy.

The effect of reduced size on the elastic properties measured on silver and lead nanowires and on polypyrrole nanotubes with an outer diameter ranging between 30 and 250 nm is presented and discussed. Resonant-contact atomic force microscopy (AFM) is used to measure their apparent elastic modulus. The measured modulus of the nanomaterials with smaller diameters is significantly higher than that of the larger ones. The latter is comparable to the macroscopic modulus of the materials. The increase of the apparent elastic modulus for the smaller diameters is attributed to surface tension effects. The surface tension of the probed material may be experimentally determined from these AFM measurements.

/pdf/surface-tension-effect-on-the-mechanical-properties-of-4a865n3ja5.pdf

Surface tension effect on the mechanical properties of nanomaterials measured by atomic force microscopy

We present a novel method for nanometer resolution subsurface imaging. When a sample of atomic force microscope (AFM) is vertically vibrated at ultrasonic frequencies much higher than the cantilever resonance, the tip cannot vibrate but it is cyclically indented into the sample. By modulating the amplitude of ultrasonic vibration, subsurface features are imaged from the cantilever deflection vibration at the modulation frequency. By adding low‐frequency lateral vibration to the ultrasonic vibration, subsurface features with different shear rigidity are imaged from the torsional vibration of cantilever. Thus controlling the direction of vibration forces, we can discriminate subsurface features of different elastic properties.

Ultrasonic force microscopy for nanometer resolution subsurface imaging

The electrical conduction of self-assembled monolayers (SAMs) made from conjugated molecules was measured using conductive atomic force microscopy (AFM), with a focus on the molecular structural ef...

Electrical Conduction of Conjugated Molecular SAMs Studied by Conductive Atomic Force Microscopy

A depth-sensing indentation system was used to measure the residual stress in a stainless steel plate implanted by Fe2+ ions with an energy of 3 MeV at a dose of 3 × 1016 cm−2. Unlike other measurement methods, such as substrate curvature and X-ray diffraction techniques, depth-sensing indentation provides an accurate measurement of local residual surface stresses in the thin ion-implanted layer. Micromechanical analysis was carried out based on the premise that elastic unloading responses during indentation are fully independent of any pre-existing residual stresses at the indented surface. The correctness of this premise was verified by FEM simulation. It is found that the surface stress is proportional to the load shift induced by the surface stress. By using the energy method, a formula was derived for determining the surface stress by depth-sensing indentation studies. The residual surface stress induced by ion implantation was evaluated by using this formula.

Indentation method to measure the residual stress induced by ion implantation

We examined, both theoretically and experimentally, the characteristics of subsurface imaging with nanometer resolution and the effect of contact elasticity in the ultrasonic force microscope (UFM). In particular, the effect of the surface energy and effective elasticity on the maximum tip-sample force and the shift of the averaged tip-sample distance were examined. Furthermore, kink formation in the cantilever deflection (z a) against the ultrasonic frequency vibration (UFV) amplitude (a) characteristics was predicted. This model was used to explain experimental observations in UFM, such as the features of the measured z a(a) curve and the damping of the cantilever torsion vibration by the UFV. Moreover, the previously reported lateral ultrasonic force microscope image of subsurface features was explained by the response of subsurface edge dislocation to a large instantaneous force enhanced by the UFV.

https://iopscience.iop.org/article/10.1143/JJAP.33.3197/pdf

Analysis of Subsurface Imaging and Effect of Contact Elasticity in the Ultrasonic Force Microscope

Carbon-related materials are prepared using various physical vapor deposition (PVD) methods. High-power impulse magnetron sputtering is a PVD method that uses glow plasma and this method is employed to prepare diamond-like carbon (DLC) films. The densities of the glow current and the consumed power for an effective area of plasma generation are 1.4 ${\rm A}/{\rm cm}^{2}$ and 1.2 ${\rm kW}/{\rm cm}^{2}$ , respectively. A pulsed bias is applied to the substrate (subsequently called substrate bias voltage). The pressures of the background gas and the substrate bias voltages influence the surface morphology and the roughness of the deposited films. It is discovered that a critical pressure of 0.3 Pa and a critical bias voltage of ${-}{\rm 100}~{\rm V}$ is needed to change the DLC film characterization. A drastic change in these characteristics is seen for pressures ${ ; a bumping surface and dumpling-like aggregations are produced. In addition, there is a bias-voltage dependency on these films, as smoother surfaces are seen in a bias-voltage range that is higher than ${-}{\rm 100}~{\rm V}$ . This phenomenon may be related to the DLC structure, which is evaluated by Raman parameters of the deposited films. It is found that the position and the full width at half maximum of the graphite peak show a minimum and a maximum, respectively, at a bias voltage of ${-}{\rm 100}~{\rm V}$ . The results of X-ray photoemission spectroscopy reveal that the ${\rm sp}^{3}$ bond ratio indicates a maximum at a pressure of 0.3 Pa and at a bias voltage of ${-}{\rm 100}~{\rm V}$ . Thus, it is clear that the gas pressure of 0.3 Pa and the bias voltage of ${-}{\rm 100}~{\rm V}$ are critical values that change the pressure and bias dependence of the film characteristics.

Hisato Ogiso

Papers

Ultrasonic force microscopy for nanometer resolution subsurface imaging

Electrical Conduction of Conjugated Molecular SAMs Studied by Conductive Atomic Force Microscopy

Indentation method to measure the residual stress induced by ion implantation

Analysis of Subsurface Imaging and Effect of Contact Elasticity in the Ultrasonic Force Microscope

DLC Coating by HiPIMS: The Influence of Substrate Bias Voltage