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Full-Text Articles in Physics

Investigation Of The Probe-Sample Interaction In The Ultrasonic/Shear-Force Microscope: The Phononic Friction Mechanism, Xiquan Cui, Andres H. La Rosa Dec 2005

Investigation Of The Probe-Sample Interaction In The Ultrasonic/Shear-Force Microscope: The Phononic Friction Mechanism, Xiquan Cui, Andres H. La Rosa

Physics Faculty Publications and Presentations

The dissipative and conservative interactions between a sharp probe and a flat Si sample in the ultrasonic/shear-force microscope are investigated. It is shown that, when working in the ambient condition, there are two distinct probe-sample interaction regions: the pure dissipative interaction region in the relatively far probe-sample distance, and the highly correlated dissipative and conservative interaction region in the close probe-sample distance. The ultrasonic data suggest that the phonon generation is a dissipative channel for the probe-sample interaction in the shear force microscope. A shaking potential model is proposed to explain the phononic friction mechanism


High-Resolution Angular Measurement Using Surface-Plasmon-Resonance Via Phase Interrogation At Optimal Incident Wavelengths, P.T. Leung, Hai-Pang Chiang, Jing-Lun Lin, Railing Chang, Sheng-Yu Su Oct 2005

High-Resolution Angular Measurement Using Surface-Plasmon-Resonance Via Phase Interrogation At Optimal Incident Wavelengths, P.T. Leung, Hai-Pang Chiang, Jing-Lun Lin, Railing Chang, Sheng-Yu Su

Physics Faculty Publications and Presentations

It is demonstrated that ultrahigh-resolution angular measurement can be achieved via surface-plasmon-resonance excitation in which the phase difference between p- and s-polarized reflected waves is monitored as a function of the incidence angle. Resolutions down to 1.9 x 10(-6) deg are obtained by performing the measurements at optimal incident wavelengths. This represents an order of magnitude improvement compared with previously reported values.


The Ultrasonic/Shear-Force Microscope: Integrating Ultrasonic Sensing Into A Near-Field Scanning Optical Microscope, Andres H. La Rosa, Xiquan Cui, J. Mccollum, Nan Li, Richard Nordstrom Sep 2005

The Ultrasonic/Shear-Force Microscope: Integrating Ultrasonic Sensing Into A Near-Field Scanning Optical Microscope, Andres H. La Rosa, Xiquan Cui, J. Mccollum, Nan Li, Richard Nordstrom

Physics Faculty Publications and Presentations

An ultrasonic transducer is incorporated into a near-field scanning optical microscope (NSOM) to augment its versatility to characterize the properties of layers adsorbed to a sample's surface. Working under typical NSOM operation conditions, the ultrasonic transducer--attached underneath the sample--demonstrates sufficient sensitivity to monitor the waves generated by the tapered NSOM probe that oscillates in the proximity of, and parallel to, the sample's top surface. This capability makes the newly integrated ultrasonic/shear-force microscope a valuable diagnostic tool in the study of sliding friction and surface phenomena in general. Here, it is used to concurrently and independently monitor the ...


Erratum: "Environmental Swap Energy And Role Of Configurational Entropy In Transfer Of Small Molecules From Water Into Alkanes", Pavel Smejtek, Robert Campbell Word Jun 2005

Erratum: "Environmental Swap Energy And Role Of Configurational Entropy In Transfer Of Small Molecules From Water Into Alkanes", Pavel Smejtek, Robert Campbell Word

Physics Faculty Publications and Presentations

Presents correction to an article related to configurational entropy in transfer of small molecules from water into alkanes, published in the 2005 issue of "The Journal Chemical Physics" and is available online at: http://archives.pdx.edu/ds/psu/8364


Self-Induced Decoherence Approach: Strong Limitations On Its Validity In A Simple Spin Bath Model And On Its General Physical Relevance, Maximillian Schlosshauer Jan 2005

Self-Induced Decoherence Approach: Strong Limitations On Its Validity In A Simple Spin Bath Model And On Its General Physical Relevance, Maximillian Schlosshauer

Physics Faculty Publications and Presentations

The "self-induced decoherence" (SID) approach suggests that (1) the expectation value of any observable becomes diagonal in the eigenstates of the total Hamiltonian for systems endowed with a continuous energy spectrum, and (2), that this process can be interpreted as decoherence. We evaluate the first claim in the context of a simple spin bath model. We find that even for large environments, corresponding to an approximately continuous energy spectrum, diagonalization of the expectation value of random observables does in general not occur. We explain this result and conjecture that SID is likely to fail also in other systems composed of ...


Making Sense Of Nanocrystal Lattice Fringes, P. Fraundorf, Wentao Qin, Peter Moeck, Eric Mandell Jan 2005

Making Sense Of Nanocrystal Lattice Fringes, P. Fraundorf, Wentao Qin, Peter Moeck, Eric Mandell

Physics Faculty Publications and Presentations

The orientation dependence of thin-crystal lattice fringes can be gracefully quantified using fringe-visibility maps, a direct-space analog of Kikuchi maps [Nishikawa and Kikuchi, Nature (London) 121, 1019 (1928)]. As in navigation of reciprocal space with the aid of Kikuchi lines, fringe-visibility maps facilitate acquisition of crystallographic information from lattice images. In particular, these maps can help researchers to determine the three-dimensional lattice of individual nanocrystals, to 'fringe-fingerprint' collections of randomly oriented particles, and to measure local specimen thickness with only a modest tilt. Since the number of fringes in an image increases with maximum spatial-frequency squared, these strategies (with help ...


Infrared Response Of Charge-Coupled Devices, Matthias Loch, Ralf Widenhorn, Erik Bodegom Jan 2005

Infrared Response Of Charge-Coupled Devices, Matthias Loch, Ralf Widenhorn, Erik Bodegom

Physics Faculty Publications and Presentations

With a band gap of silicon of 1.1eV, the largest wavelength that can excite electrons from the valence to the conduction band is roughly 1100nm. As a consequence, in, for instance, a charge-coupled device, the quantum efficiency (QE) for wavelengths larger than 1100nm is assumed to be zero. We found that there is a response at those longer wavelengths and that the response decreases with increasing wavelength. The QE increases with increasing chip temperature which suggests a thermally activated process. Impurities in the silicon provide the energy levels in the band gap, from which electrons can be excited either ...


The Ultrasonic/Shear-Force Microscope: A Metrology Tool For Surface Science And Technology, Andres H. La Rosa, Nan Li, K. Asante Jan 2005

The Ultrasonic/Shear-Force Microscope: A Metrology Tool For Surface Science And Technology, Andres H. La Rosa, Nan Li, K. Asante

Physics Faculty Publications and Presentations

This paper describes recent results obtained with the Ultrasonic/Shear-Force Microscope (SUNM), an analytical tool suitable for investigating the quite different dynamic displayed by fluid-like films when subjected to mesoscopic confinement and while in intimate contact with two sliding solid boundaries. The SUNM uses two sensory modules to concurrently but independently monitor the effects that fluid-mediated interactions exert on two sliding bodies: the microscope’s sharp probe (attached to a piezoelectric sensor) and the analyzed sample (attached to an ultrasonic transducer). This dual capability allows correlating the fluid-like film’s viscoelastic properties with changes in the probe’s resonance frequency ...