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16 Sep 2002

Volume 81, Issue 12, pp. 2145-2305

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Dynamic higher-order correction of acoustic aberration due to material microstructure

S. D Sharples, M. Clark, and M. G. Somekh

Appl. Phys. Lett. 81, 2288 (2002); http://dx.doi.org/10.1063/1.1507827 (3 pages) | Cited 3 times

Online Publication Date: 9 September 2002

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Material microstructure, such as grains in metals, can perturb ultrasound as it propagates through—or on the surface of—the material. This acoustic aberration affects the accuracy and reliability of ultrasound measurements and is a fundamental limit to resolution for many materials. Using an all-optical approach to generation and detection of surface acoustic waves, we detect the acoustic wave front aberrations, and correct for them by calculating a different generation profile, which is imaged onto the material using a spatial light modulator. © 2002 American Institute of Physics.
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43.35.Pt Surface waves in solids and liquids
43.25.Fe Effect of nonlinearity on acoustic surface waves
68.35.Iv Acoustical properties
62.65.+k Acoustical properties of solids
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
43.58.Ls Acoustical lenses and microscopes
42.79.Hp Optical processors, correlators, and modulators
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.60.Qv Signal processing instrumentation, integrated systems, smart transducers, devices and architectures, displays and interfaces for acoustic systems

Near-field photoluminescence imaging of single semiconductor quantum constituents with a spatial resolution of 30 nm

K. Matsuda, T. Saiki, S. Nomura, M. Mihara, and Y. Aoyagi

Appl. Phys. Lett. 81, 2291 (2002); http://dx.doi.org/10.1063/1.1507357 (3 pages) | Cited 26 times

Online Publication Date: 9 September 2002

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High-resolution photoluminescence (PL) imaging of semiconductor quantum dots (QDs) was demonstrated using a low-temperature near-field scanning optical microscope. We systematically evaluated the spatial resolution for various fiber probes with different aperture diameters ranging from 30 to 135 nm. We achieved a spatial resolution of 30 nm ( ∼ λ/30:λ = 930 nm) in the PL imaging of self-assembled InAs QDs due to both improvement in probe preparation and optimization of the sample structure. The spatial resolution obtained in this study is on the scale of semiconductor quantum constituents and will make it possible to map out and manipulate the wave function in quantum-confined systems. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
78.55.-m Photoluminescence, properties and materials

Free-space detection of terahertz radiation using crystalline and polycrystalline ZnSe electro-optic sensors

J. F. Holzman, F. E. Vermeulen, S. E. Irvine, and A. Y. Elezzabi

Appl. Phys. Lett. 81, 2294 (2002); http://dx.doi.org/10.1063/1.1508435 (3 pages) | Cited 13 times

Online Publication Date: 9 September 2002

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We present an experimental investigation demonstrating the use of single-crystal and polycrystalline ZnSe for the detection of freely propagating terahertz (THz) radiation. It is found that polycrystalline ZnSe electro-optic sensors exhibit preferred crystallographic orientations and can provide high bandwidth detection capabilities. The polycrystalline grain size and orientation are shown to be important in detecting distortion-free THz wave forms. By proper choice of the polycrystalline sensor thickness, a THz detection bandwidth comparable to that obtained with a single-crystal sensor is demonstrated. The application of polycrystalline material for free-space electro-optic sampling (FS–EOS) permits the possibility of utilizing nonlattice-matched thin-film integrated THz FS–EOS sensors and generators. © 2002 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
78.20.Jq Electro-optical effects
78.66.Hf II-VI semiconductors
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Utilization of sputter depth profiling for the determination of band alignment at polycrystalline CdTe/CdS heterointerfaces

J. Fritsche, T. Schulmeyer, D. Kraft, A. Thißen, A. Klein, and W. Jaegermann

Appl. Phys. Lett. 81, 2297 (2002); http://dx.doi.org/10.1063/1.1507830 (3 pages) | Cited 10 times

Online Publication Date: 9 September 2002

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The band alignment at polycrystalline CdS/CdTe heterointerfaces for thin-film solar cells is determined by photoelectron spectroscopy from stepwise CdTe deposition on polycrystalline CdS substrates and from subsequent sputter depth profiling. Identical values of 0.94±0.05 eV for the valence band offset are obtained. © 2002 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
84.60.Jt Photoelectric conversion
79.60.Jv Interfaces; heterostructures; nanostructures

Molecular rectification at 8 K in an Au/C16H33Q-3CNQ LB film/ Au structure

Nobuharu Okazaki, J. Roy Sambles, Michael J. Jory, and Geoffrey J. Ashwell

Appl. Phys. Lett. 81, 2300 (2002); http://dx.doi.org/10.1063/1.1508815 (3 pages) | Cited 19 times

Online Publication Date: 9 September 2002

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The nonlinear I/V characteristics of a molecular rectifier structure of the form Au/20 layers of C16H33Q-3CNQ/Au have been explored from 8 to 300 K. At 8 K the voltage-controlled nonlinear conduction is explored in the absence of thermal effects. At the highest voltages (±15 V) at 8 K the rectification ratio was about 4 with current densities as high as 1000 A m−2 and log I varying as ∣V∣0.5, indicating voltage-controlled hopping. The likely explanation for the complete I/V characteristics rests with the insulating aliphatic tails, which provide substantial electrical barriers within the structure. © 2002 American Institute of Physics.
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73.40.Rw Metal-insulator-metal structures
73.40.Ei Rectification
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Fq High-field and nonlinear effects

Electrostatic stabilization of fluid microstructures

Frieder Mugele and Stephan Herminghaus

Appl. Phys. Lett. 81, 2303 (2002); http://dx.doi.org/10.1063/1.1508808 (3 pages) | Cited 44 times

Online Publication Date: 9 September 2002

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A liquid surface of arbitrary shape is, in general, dynamically unstable due to gradients in Laplace pressure. This greatly limits the class of morphologies eligible for artificial fluid microstructures. In this work, we demonstrate that a wide class of these otherwise unstable surface morphologies can be stabilized using electrostatic fields. Complex stable fluid microstructures were generated in a conventional electrowetting setup operated at high voltage. We present an electrostatic model that explains the stability and the scale of the stable structures as a function of external control parameters. The stability as well as the universality of these structures naturally leads to novel concepts in microfluidic technology. © 2002 American Institute of Physics.
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47.65.-d Magnetohydrodynamics and electrohydrodynamics
68.08.Bc Wetting
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
47.85.Np Fluidics
61.25.-f Studies of specific liquid structures
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