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25 Oct 2004

Volume 85, Issue 17, pp. 3657-3939

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 3851 (2004); http://dx.doi.org/10.1063/1.1808886 (3 pages)

P. Guha, S. Kar, and S. Chaudhuri
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Subnanometric measurements of evanescent wave penetration depth using total internal reflection microscopy combined with fluorescent correlation spectroscopy

S. Harlepp, J. Robert, N. C. Darnton, and D. Chatenay

Appl. Phys. Lett. 85, 3917 (2004); http://dx.doi.org/10.1063/1.1802374 (3 pages) | Cited 7 times

Online Publication Date: 29 October 2004

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In total internal reflection microscopy (TIRM), quantitative interpretation of results often requires a precise knowledge of the penetration depth of the evanescent wave. Standard TIRM practice is to calculate this depth from the microscope’s geometry, but this can introduce significant errors. We show how to calibrate the penetration depth of an evanescent wave in TIRM. An evanescent wave is obtained by illuminating a surface at an incident angle greater than the critical angle. Its penetration depth generally depends on the wavelength and the incident angle of the illumination, and on the indices of refraction on either side of the reflecting suface, but cannot be larger than the field of view. By introducing a fluorescent species (such as fluorescein) and measuring its diffusion time, it is possible to measure very precisely the penetration depth of the evanescent wave.
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87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics
87.15.M- Spectra of biomolecules

Multilayer three-dimensional photolithography with traditional planar method

Peng Yao, Garrett J. Schneider, Binglin Miao, Janusz Murakowski, Dennis W. Prather, Eric D. Wetzel, and Daniel J. O’Brien

Appl. Phys. Lett. 85, 3920 (2004); http://dx.doi.org/10.1063/1.1811773 (3 pages) | Cited 4 times

Online Publication Date: 29 October 2004

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We describe and demonstrate a method for the realization of three-dimensional lithography through the use of repeated planar photolithography processes. This process is based on the use of a commercially available resist system and consists of tailoring the resist response by controlling the exposure, development, and baking aspects of the process. In particular, postexposure bake is studied in detail as a primary working mechanism which, when combined with a small UV exposure and strong absorption, vertically confined photoacid is produced. As a result, the possibility of re-exposure in lower layers during top layer exposure is eliminated. In the course of this letter, we discuss issues related to this process and how they were overcome. Last, as a demonstration of the proposed method, we present three- and four-layer, three-dimensional “woodpile” photonic crystal structures.
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42.70.Qs Photonic bandgap materials
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer

Parametric excitation of circular micromachined polycrystalline silicon disks

Ville Kaajakari and Amit Lal

Appl. Phys. Lett. 85, 3923 (2004); http://dx.doi.org/10.1063/1.1807951 (3 pages) | Cited 5 times

Online Publication Date: 29 October 2004

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Center anchored polycrystalline silicon plates are parametrically excited using ultrasonic substrate motion generated by a lead zirconate titanate oxide (PZT) plate bonded to the silicon die. Parametric excitation is used to achieve large amplitude, greater than 100 nm, transverse plate vibrations in atmospheric pressure with sub-3 VPP drive on the PZT plate with corresponding surface velocities over 1.5 m/s. The preferred parametrically excited modes are observed to be “whispering gallery” plate modes with no radial nodal points. The possible nonlinear mechanisms are analyzed and the parametric excitation is explained with in-plane plate stresses due to the lateral plate anchor motion. The effect of in-plane stresses is modeled with von Kármán plate equations. Parametric instability is demonstrated with the use of nonlinear Floquet transition matrix.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
43.38.-p Transduction; acoustical devices for the generation and reproduction of sound

Kelvin probe force microscopy as a tool for characterizing chemical sensors

R. Grover, B. Mc Carthy, Y. Zhao, G. E. Jabbour, D. Sarid, G. M. Laws, B. R. Takulapalli, T. J. Thornton, and D. Gust

Appl. Phys. Lett. 85, 3926 (2004); http://dx.doi.org/10.1063/1.1810209 (3 pages) | Cited 4 times

Online Publication Date: 29 October 2004

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We report on the use of Kelvin probe force microscopy in measuring the shift of the contact potential difference of micron-scale areas. The experimental results provide important information required for understanding and modeling the electrical characteristics of chemically sensitive field-effect transistors (ChemFETs). The temporal evolution in the shift of the contact potential difference of chemically sensitive monolayers of free-base porphyrin and zinc-porphyrin on exposure to pyridine gas was studied and their different behavior observed. The Kelvin probe force microscopy data on nanometer-scale areas were in agreement with those obtained with a conventional Kelvin probe on centimeter-scale areas. The accuracy of the measured shift in contact potential difference upon exposure to trace amounts of gas indicates the utility of Kelvin probe force microscopy as a means to characterize the operation of exposed-gate ChemFETs.
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07.79.Lh Atomic force microscopes
73.40.Cg Contact resistance, contact potential
82.80.-d Chemical analysis and related physical methods of analysis
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Scanning probe microscopy with inherent disturbance suppression

A. W. Sparks and S. R. Manalis

Appl. Phys. Lett. 85, 3929 (2004); http://dx.doi.org/10.1063/1.1812377 (3 pages) | Cited 7 times

Online Publication Date: 29 October 2004

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We introduce a general approach for inherently suppressing out-of-plane disturbances in scanning probe microscopy that enables higher-resolution imaging, particularly in noisy environments. In this approach, two distinct sensors simultaneously measure the probe–sample separation. One sensor measures a spatial average over a large sample area while the other responds locally to topography underneath the nanometer-scale probe. When the localized sensor is used to control the probe–sample separation in feedback, the spatially distributed sensor signal reveals only topography. We implemented this approach on a scanning tunneling microscope using a microcantilever with an integrated tunneling tip and interferometer. For disturbances applied normal to the sample, we measure −50 dB of disturbance suppression at 1 Hz, compared to 0 dB with conventional imaging.
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07.79.Cz Scanning tunneling microscopes
07.60.Ly Interferometers
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

The photocapacitor: An efficient self-charging capacitor for direct storage of solar energy

Tsutomu Miyasaka and Takurou N. Murakami

Appl. Phys. Lett. 85, 3932 (2004); http://dx.doi.org/10.1063/1.1810630 (3 pages) | Cited 27 times

Online Publication Date: 29 October 2004

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A light-driven self-charging capacitor was fabricated as an efficient solar energy storage device. The device, which we name the photocapacitor, achieves in situ storage of visible light energy as an electrical power at high quantum conversion efficiency. The photocapacitor was constructed on a multilayered photoelectrode comprising dye-sensitized semiconductor nanoparticles/hole-trapping layer/activated carbon particles in contact with an organic electrolyte solution, in which photogenerated charges are stored at the electric double layer. Repeated charge-discharge cycles with a charging voltage of >0.45 V yielded a capacitance of 0.69 F cm−2.
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84.60.Ve Energy storage systems, including capacitor banks

Evaluation of the effectiveness of back-side damage gettering in silicon introduced by a cavitating jet

H. Kumano, T. Sasaki, and H. Soyama

Appl. Phys. Lett. 85, 3935 (2004); http://dx.doi.org/10.1063/1.1808499 (3 pages) | Cited 5 times

Online Publication Date: 29 October 2004

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Photocapacitance measurements have been performed to evaluate the electrical effectiveness of gettering by back-side damage, introduced by a cavitating jet into silicon wafers. The silicon wafers, which had their back sides damaged previously in localized areas, were intentionally contaminated and subsequently thermally treated to diffuse the contamination through the wafer. The density of deep levels varied between the areas with back-side damage and those without. The results obtained on back-side damaged areas were closer to those on the original starting material. These results confirm that the back-side damage introduced by a cavitating jet can function as gettering sites.
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81.05.Cy Elemental semiconductors
81.65.Tx Gettering
61.72.Yx Interaction between different crystal defects; gettering effect
72.40.+w Photoconduction and photovoltaic effects
68.35.Fx Diffusion; interface formation
71.55.Cn Elemental semiconductors
68.47.Fg Semiconductor surfaces
81.40.Gh Other heat and thermomechanical treatments
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