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17 Feb 2003

Volume 82, Issue 7, pp. 1003-1136

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 1069 (2003); http://dx.doi.org/10.1063/1.1544428 (3 pages)

M. L. Povinelli, Steven G. Johnson, J. D. Joannopoulos, and J. B. Pendry
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Electrostatic response of hydrophobic surface measured by atomic force microscopy

O. Teschke and E. F. de Souza

Appl. Phys. Lett. 82, 1126 (2003); http://dx.doi.org/10.1063/1.1542945 (3 pages) | Cited 10 times

Online Publication Date: 10 February 2003

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The arrangement of water molecules at aqueous interfaces is an important question in material and biological sciences. We have measured the force acting on neutral tips as a function of the distance to hydrophobic silicon surfaces and cetyltrimethylammonium bromide monolayers covering mica surfaces in aqueous solutions. The unusually large magnitude of this force is attributed to an electrostatic response of the aqueous fluid structure (hydration layer) which is generated by the reorientation of water molecular dipoles. The exchange of a volume of this region with a dielectric permittivity (εint) by the tip with a dielectric permittivity (εtip) is responsible for the tip attraction when it is immersed in the polarization (hydration) layer. Variable permittivity profiles starting at ε ≈ 11 at the interface and increasing to ε = 80 about 10 nm from hydrophobic silicon surfaces and about 50 nm from cetyltrimethylammonium bromide monolayer covering mica surfaces were measured. © 2003 American Institute of Physics.
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68.35.Md Surface thermodynamics, surface energies
68.37.Ps Atomic force microscopy (AFM)
68.03.Cd Surface tension and related phenomena
68.47.Fg Semiconductor surfaces
68.47.Gh Oxide surfaces
77.22.Ch Permittivity (dielectric function)
82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)

Demonstration of bottom mirrors for resonant-cavity-enhanced GaAs homojunction far-infrared detectors

Y. H. Zhang, H. T. Luo, and W. Z. Shen

Appl. Phys. Lett. 82, 1129 (2003); http://dx.doi.org/10.1063/1.1553992 (3 pages) | Cited 4 times

Online Publication Date: 10 February 2003

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A proposal for the bottom mirrors of resonant-cavity-enhanced GaAs homojunction far-infrared (FIR) detectors has been suggested and optimized based on undoped/doped GaAs layers with the Fresnel matrix method. With this kind of bottom mirror, the calculated absorption probability in the detector cavity increases two times over that in the normal detector structure. Comparing optical measurements have been carried out on n-GaAs homojunction FIR detector structures with and without the bottom mirrors, as well as a single optimized bottom mirror structure (without the detector cavity structure). The experimental FIR reflection and transmission results demonstrate well the theoretical design. © 2003 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Bh Lenses, prisms and mirrors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Photomodulated thermoreflectance investigation at elevated temperatures: plasma versus thermal effect

Constantinos Christofides, Andreas Othonos, and Efi Loizidou

Appl. Phys. Lett. 82, 1132 (2003); http://dx.doi.org/10.1063/1.1541935 (3 pages)

Online Publication Date: 10 February 2003

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Photomodulated thermoreflectance measurements were performed at elevated temperatures (294 to 623 K), on crystalline silicon lightly doped with boron. The temperature dependence is qualitatively and quantitatively discussed. The “competition” between thermal and plasma contribution, as a function of temperature, is one of the main subjects of this letter. © 2003 American Institute of Physics.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
81.05.Cy Elemental semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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