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31 May 2004

Volume 84, Issue 22, pp. 4361-4576

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 4409 (2004); http://dx.doi.org/10.1063/1.1757648 (3 pages)

Azita Soleymani, Piroz Zamankhan, and William Polashenski
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Neurons culturing and biophotonic sensing using porous silicon

S. Ben-Tabou de Leon, A. Sa’ar, R. Oren, M. E. Spira, and S. Yitzchaik

Appl. Phys. Lett. 84, 4361 (2004); http://dx.doi.org/10.1063/1.1741032 (3 pages) | Cited 15 times

Online Publication Date: 12 May 2004

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We report on culturing of Aplysia neurons on porous silicon substrates. Good adhesion of the neurons to the porous silicon substrate and a formation of neuron-semiconductor contact have been accomplished. Cultured neurons survived for at least one week on porous silicon showing normal passive membrane properties and generation of action potentials. We have investigated the possibility of using the photoluminescence from porous silicon for transducing neuronal activity into photonic signals. We found that photoluminescence quenching occurs for cathodic current polarization using aqueous salt-based liquid solution contact. The quenching process is due to diffusion of electrons into the porous silicon, giving rise to Auger nonradiative recombination in the silicon nanocrystallites. The decay time of the photoluminescence was found to be relatively slow due to diffusive nature of the process. © 2004 American Institute of Physics.
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87.16.D- Membranes, bilayers, and vesicles
87.85.J- Biomaterials
78.55.-m Photoluminescence, properties and materials
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X-ray absorption study of the electronic structure of Li-excess spinel Li1+xTi2−xO4 (0 ⩽ x ⩽ 0.33)

Wonkyung Ra, Masanobu Nakayama, Hiromasa Ikuta, Yoshiharu Uchimoto, and Masataka Wakihara

Appl. Phys. Lett. 84, 4364 (2004); http://dx.doi.org/10.1063/1.1755418 (3 pages) | Cited 4 times

Online Publication Date: 12 May 2004

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Li-excess spinel oxide, Li1+xTi2−xO4 (0 ⩽ x ⩽ 0.33), was investigated by x-ray absorption spectra (XAS) technique. XAS results revealed that both oxygen and titanium ions affect electronic structural changes in the system. Early transition metal compounds are considered to have smaller d–d Coulomb correlation energy (Udd) than p–d Charge-transfer energy (Δ), indicating that electronic transfer for charge compensation occurs mainly on transition metal. However, present XAS results show that considerable charge-transfer character due to strong hybridization between titanium 3d and oxygen 2p orbitals exists in this early transition metal oxide system. © 2004 American Institute of Physics.
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78.70.Dm X-ray absorption spectra
71.20.-b Electron density of states and band structure of crystalline solids

Correlated stacks of CdSe/ZnSSe quantum dots

Th. Schmidt, T. Clausen, J. Falta, G. Alexe, T. Passow, D. Hommel, and S. Bernstorff

Appl. Phys. Lett. 84, 4367 (2004); http://dx.doi.org/10.1063/1.1756195 (3 pages) | Cited 6 times

Online Publication Date: 12 May 2004

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The observation and quantitative investigation of the spatial correlation of CdSe quantum dots in stacked CdSe/ZnSSe quantum-dot layers is reported. Using grazing incidence x-ray small angle scattering, the influence of the ZnSSe spacer layer thickness ranging from 20 to 80 Å, as well as the influence of the stacking number (3–10) has been analyzed. Satellite spots, indicative of quantum-dot ordering, have been observed for a spacer thickness of up to 45 Å, and for a stacking number of at least 5. This finding can be explained by a self-organized ordering process driven by the lattice mismatch induced strain. A mean lateral quantum-dot distance ranging from 116 to 145 Å, depending on the spacer thickness, has been found. In addition, an anisotropy of twofold symmetry has been observed, with the strongest correlation signal along 〈1math0〉. © 2004 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
61.05.cf X-ray scattering (including small-angle scattering)
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Quantum confinement for large light output from pure semiconducting scintillators

Kengo Shibuya, Masanori Koshimizu, Keisuke Asai, and Hiromi Shibata

Appl. Phys. Lett. 84, 4370 (2004); http://dx.doi.org/10.1063/1.1756203 (3 pages) | Cited 3 times

Online Publication Date: 12 May 2004

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A method for creating a fast scintillator is proposed. Recently, much attention has been paid to pure semiconductors during development of subnanosecond fast solid scintillators. However, the bulky samples rarely exhibit high light yields at room temperature because of thermal instability at the excitonic levels. The authors employed the optimum three- and two-dimensional semiconducting systems provided by lead-halide-based compounds to demonstrate the advantage of low dimensionality in the scintillating efficiency. Their dimensional and temperature dependencies were investigated using a high-energy proton beam. Consequently, the quantum confinement system clearly prevented thermal quenching from excitonic level even at room temperature, and the result proposes the next breakthrough to create ultrafast solid scintillators. © 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices
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Interaction of Fe+ with the C60 surface: A study about the feasibility of endohedral doping

P. Reinke, S. Eyhusen, M. Büttner, and P. Oelhafen

Appl. Phys. Lett. 84, 4373 (2004); http://dx.doi.org/10.1063/1.1756204 (3 pages)

Online Publication Date: 12 May 2004

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The feasibility of endohedral iron doping of C60 is studied using a mass selected ion beam to create an Fe+ beam with variable energy (60–380 eV, 1.2×10−3 C) which is directed at a C60 thin film. The surface is characterized by x-ray photoelectron spectroscopy, and oxidation of the samples is used to discriminate between FeC60 and carbides. The fullerene cages are damaged during the irradiation, and participate in direct Fe–C bond formation. The reaction with oxygen indicates the absence of sizable amount of FeC60. Comparison with reference samples composed of iron and damaged fullerene layers (by Ar+ irradiation) supports this interpretation. The experiment serves as a model study for the investigation of different metal-fullerene combinations. © 2004 American Institute of Physics.
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61.72.up Other materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
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Photocurrent in ZnO nanowires grown from Au electrodes

Kihyun Keem, Hyunsuk Kim, Gyu-Tae Kim, Jong Soo Lee, Byungdon Min, Kyoungah Cho, Man-Young Sung, and Sangsig Kim

Appl. Phys. Lett. 84, 4376 (2004); http://dx.doi.org/10.1063/1.1756205 (3 pages) | Cited 121 times

Online Publication Date: 12 May 2004

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ZnO nanowires were grown between two Au electrodes on an Al2O3-deposited Si wafer. Photoresponse, photoresponse spectrum, and current–voltage (I–V) studies were performed for the investigation into photoconduction mechanism in these nanowires. The photoresponse of the nanowires under the continuous illumination of light with above- or below-gap energies was slow, which indicates that photocurrent in the nanowires is surface-related rather than bulk-related. The photoresponse spectrum represents the above- and below-gap absorption bands for the photocurrents. The I–V characteristics under the illumination of the above-gap light are ohmic, but the characteristics under the illumination of the below-gap light are Schottky. This observation indicates that the above-gap light lowers the potential barrier built in the contact between the ZnO nanowires and electrodes, but that the below-gap light does not lower the potential barrier. © 2004 American Institute of Physics.
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73.63.Nm Quantum wires
73.50.Pz Photoconduction and photovoltaic effects
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Enhancement of the green, visible Tb3+ luminescence from Tb-doped silicon-rich silicon oxide by C co-doping

Se-Young Seo and Jung H. Shin

Appl. Phys. Lett. 84, 4379 (2004); http://dx.doi.org/10.1063/1.1757015 (3 pages) | Cited 4 times

Online Publication Date: 12 May 2004

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The effect of C co-doping on the Tb3+ luminescence from Tb-doped silicon-rich silicon oxide (SRSO) films is investigated. Tb-doped SRSO films co-doped with C (SRSO:C) were deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition. The Tb3+ photoluminescence intensity is enhanced by the presence of nanocluster Si (nc-Si), and C co-doping further increases the Tb3+ photoluminescence intensity by more than an order of magnitude. The maximum enhancement is observed at the C content of ∼5 at. %, at which the Tb3+ luminescence is bright enough to be observed by the naked eye under ambient conditions. The 543 nm Tb3+ lifetimes were in the range of 0.5–1.2 ms, comparable to those from Tb-doped silica. Based on the results, we conclude that nanometer-sized nc-Si can excite Tb3+ ions via an Auger-type energy transfer, and that C co-doping greatly increases the efficiency of such exciton-mediated excitation of Tb3+. © 2004 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
71.35.-y Excitons and related phenomena
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Controlling the crystallization and magnetic properties of melt-spun Pr2Fe14B/α-Fe nanocomposites by Joule heating

Z. Q. Jin, B. Z. Cui, J. P. Liu, Y. Ding, Z. L. Wang, and N. N. Thadhani

Appl. Phys. Lett. 84, 4382 (2004); http://dx.doi.org/10.1063/1.1757017 (3 pages) | Cited 11 times

Online Publication Date: 12 May 2004

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Pr2Fe14B/α-Fe based nanocomposites have been prepared through crystallization of melt-spun amorphous Pr7Tb1Fe85Nb0.5Zr0.5B6 ribbons by means of ac Joule heating while simultaneously monitoring room-temperature electrical resistance R. The R value shows a strong variation with respect to applied current I, and is closely related to the amorphous-to-nanocrystalline phase transformation. The curve of R versus I allows one to control the crystallization behavior during Joule heating and to identify the heat-treatment conditions for optimum magnetic properties. A coercivity of 550 kA/m and a maximum energy product of 128 kJ/m3 have been obtained upon heating the amorphous ribbons at a current of 2.0 A. These properties are around 30% higher than the values of samples prepared by conventionally (furnace) annealed amorphous ribbons. © 2004 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
64.70.K- Solid-solid transitions
81.40.Gh Other heat and thermomechanical treatments
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Tm Composite materials
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Minimization of germanium penetration, nanocrystal formation, charge storage, and retention in a trilayer memory structure with silicon nitride/hafnium dioxide stack as the tunnel dielectric

T. H. Ng, W. K. Chim, W. K. Choi, V. Ho, L. W. Teo, A. Y. Du, and C. H. Tung

Appl. Phys. Lett. 84, 4385 (2004); http://dx.doi.org/10.1063/1.1757022 (3 pages) | Cited 13 times

Online Publication Date: 12 May 2004

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Trilayer structures, consisting of a rapid thermal oxide (RTO) layer (2.5 or 5 nm thick) grown on silicon, a sputtered Ge middle layer (3–20 nm thick), and a 50-nm-thick sputtered silicon oxide capping layer, exhibit significant penetration of Ge atoms into the silicon substrate for devices with the smaller (2.5 nm) RTO thickness, resulting in negligible nanocrystal formation and hence no charge storage or memory effect. The Ge penetration is minimized by replacing the RTO layer with a high dielectric constant (high-κ) silicon nitride/hafnium dioxide stack (grown by metalorganic chemical vapor deposition) having a larger physical thickness but smaller equivalent oxide thickness of 1.9 nm. Results show that the high-κ trilayer structure exhibits better charge storage capability (in terms of a lower program voltage) and better charge retention performance as compared to the RTO trilayer structure. © 2004 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.07.Bc Nanocrystalline materials
81.16.Pr Micro- and nano-oxidation
77.22.Ch Permittivity (dielectric function)
68.65.Ac Multilayers
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Opposite effects of NO2 on electrical injection in porous silicon gas sensors

Zeno Gaburro, Claudio J. Oton, Lorenzo Pavesi, and Lucio Pancheri

Appl. Phys. Lett. 84, 4388 (2004); http://dx.doi.org/10.1063/1.1757025 (3 pages) | Cited 10 times

Online Publication Date: 12 May 2004

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The electrical conductance of porous silicon fabricated with heavily doped p-type silicon is very sensitive to NO2. We show that the sign of the injection variations depends on the porous layer thickness. If the thickness is sufficiently low—of the order of few μm—the injection decreases instead of increasing. We discuss the effect in terms of an already proposed twofold action of NO2, according to which the free carrier density increases, and simultaneously the energy bands are bent at the porous silicon surface. © 2004 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
72.80.Cw Elemental semiconductors
72.80.Ng Disordered solids
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.43.Dq Amorphous semiconductors, metals, and alloys
71.20.Mq Elemental semiconductors
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All-organic dielectric-percolative three-component composite materials with high electromechanical response

Cheng Huang, Q. M. Zhang, Gal deBotton, and Kaushik Bhattacharya

Appl. Phys. Lett. 84, 4391 (2004); http://dx.doi.org/10.1063/1.1757632 (3 pages) | Cited 35 times

Online Publication Date: 12 May 2004

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By combining the high-dielectric copper phthalocyanine oligomer (PolyCuPc) and conductive polyanline (PANI) within polyurethane (PU) matrix an all-organic three-component dielectric-percolative composite with high dielectric constant is demonstrated. In this three-component composite system, the high-dielectric-constant PolyCuPc particulates enhance the dielectric constant of the PU matrix and this combined two-component dielectric matrix in turn serves as the high-dielectric-constant host for the PANI to realize percolative phenomenon and further enhance the dielectric response. As a result, an electromechanical strain of 9.3% and elastic energy density of 0.4 J/cm3 under an electric field of 20 V/μm can be induced. © 2004 American Institute of Physics.
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77.84.Lf Composite materials
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
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Negative bias-temperature instabilities in metal–oxide–silicon devices with SiO2 and SiOxNy/HfO2 gate dielectrics

X. J. Zhou, L. Tsetseris, S. N. Rashkeev, D. M. Fleetwood, R. D. Schrimpf, S. T. Pantelides, J. A. Felix, E. P. Gusev, and C. D’Emic

Appl. Phys. Lett. 84, 4394 (2004); http://dx.doi.org/10.1063/1.1757636 (3 pages) | Cited 14 times

Online Publication Date: 12 May 2004

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Negative bias-temperature instability (NBTI) in metal–oxide–semiconductor capacitors with SiOxNy/HfO2 gate dielectrics is compared to those with thermal SiO2 oxides. Activation energies for interface and oxide-trap charge densities for each device type, estimated from capacitance–voltage measurements versus temperature and electric field, lie in the range 0.2–0.4 eV. This suggests that the release of hydrogen from, e.g., oxide protrusions in Si, followed by the lateral motion of protons along the interface (activation energy ∼0.3 eV), may play a key role in NBTI. Passivation reactions between protons and Si–H can create interface traps, and proton capture by sub-oxide bonds (O vacancies) can lead to positive trapped-oxide charge. © 2004 American Institute of Physics.
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84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Rv Passivation
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Vertically aligned liquid crystal light valve controlled by double-side fringe-field switching with memory effect

C. Y. Xiang and X. W. Sun

Appl. Phys. Lett. 84, 4397 (2004); http://dx.doi.org/10.1063/1.1757639 (3 pages)

Online Publication Date: 12 May 2004

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A vertically aligned liquid crystal light valve with negative dielectric anisotropy driven by vertical field and double-side fringe field is described. The transmission of this device is not determined by the vertical field, but by the relative strength of the two fringe fields at the surfaces of top and bottom substrates. When a voltage is applied on the two plane electrodes, by connecting or disconnecting the two floating stripe electrodes, the corresponding transmission is high or low, respectively. An optical memory device based on this mechanism has been demonstrated. © 2004 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
42.79.Vb Optical storage systems, optical disks
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Guiding and bending of acoustic waves in highly confined phononic crystal waveguides

A. Khelif, A. Choujaa, S. Benchabane, B. Djafari-Rouhani, and V. Laude

Appl. Phys. Lett. 84, 4400 (2004); http://dx.doi.org/10.1063/1.1757642 (3 pages) | Cited 55 times

Online Publication Date: 12 May 2004

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We demonstrate experimentally the guiding and the bending of acoustic waves in highly confined waveguides formed by removing rods from a periodic two-dimensional lattice of steel cylinders immersed in water. Full transmission is observed for a one-period-wide straight waveguide within the full band gap of the perfect phononic crystal. However, when the waveguide width is doubled, destructive interference causes the transmission to vanish in the center of the passband. Waveguiding over a wide frequency range is obtained for a one-period-wide waveguide with two sharp 90° bends. Finite-difference time-domain computations are found to be in good agreement with the measurements. © 2004 American Institute of Physics.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
62.30.+d Mechanical and elastic waves; vibrations
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
63.20.-e Phonons in crystal lattices
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Submicron imaging with a planar silver lens

David O. S. Melville, Richard J. Blaikie, and Conrad R. Wolf

Appl. Phys. Lett. 84, 4403 (2004); http://dx.doi.org/10.1063/1.1757644 (3 pages) | Cited 59 times

Online Publication Date: 12 May 2004

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Optical imaging through a thin planar silver layer has been achieved by utilizing near-field lithography techniques. A 120 nm thick silver lens that was placed 60 nm below a patterned mask, imaged the mask’s features onto a photosensitive material located 60 nm below the silver. The entire structure was exposed from above with a mercury lamp. Features sizes as small as 350 nm (at a 700 nm period) were imaged onto the photosensitive material, demonstrating the lensing ability of the planar silver slab. © 2004 American Institute of Physics.
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42.30.-d Imaging and optical processing
85.40.Hp Lithography, masks and pattern transfer
42.79.Bh Lenses, prisms and mirrors
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Introduction and control of metastable states in elliptical and rectangular magnetic nanoelements

Xiaoxi Liu, John N. Chapman, Stephen McVitie, and Chris D. W. Wilkinson

Appl. Phys. Lett. 84, 4406 (2004); http://dx.doi.org/10.1063/1.1757647 (3 pages) | Cited 18 times

Online Publication Date: 12 May 2004

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Small elongated magnetic elements normally support near uniform magnetization distributions and switch abruptly under the influence of fields applied close to their long axes. However metastable states can be introduced in rectangular and elliptical nanoelements by applying fields parallel to their short axes. Using Lorentz microscopy and in situ magnetizing experiments we have established the conditions under which vortex states can be introduced. Their occurrence depends on the formation of a “C” rather than an “S” state as the applied field is reduced following saturation. Micromagnetic modeling provides support for the conclusions drawn from the experimental observations. © 2004 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ch Domain walls and domain structure
75.30.Cr Saturation moments and magnetic susceptibilities
75.70.Kw Domain structure (including magnetic bubbles and vortices)
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Supersonic dense granular materials in a duct flow

Azita Soleymani, Piroz Zamankhan, and William Polashenski

Appl. Phys. Lett. 84, 4409 (2004); http://dx.doi.org/10.1063/1.1757648 (3 pages) | Cited 2 times

Online Publication Date: 12 May 2004

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Both large-scale three-dimensional molecular-dynamics-type simulation and integration of hydrodynamic equations relevant to dense granular flows were performed to investigate the formation of shock waves in granular flows past a stationary wedge in a rectangular duct. No signature of supersonic flows was found at grain speeds as small as 0.1 m/s. Upon increasing the speed of the grains, the flow became supersonic where complex solid structures were observed to form in both upstream and downstream flow regions. In addition, the compression shock formed on the upper edges of the channel adjacent to the wedge and the expansion fan formed adjacent to the rear face of the wedge. Both the compression shock and expansion fan appear to be analogous to those in supersonic gases with some fundamental differences arising due to the inelastic collisions between particles in granular media. © 2004 American Institute of Physics.
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47.60.-i Flow phenomena in quasi-one-dimensional systems
47.55.Kf Particle-laden flows
47.40.Ki Supersonic and hypersonic flows
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Degenerate layers in epitaxial ZnO films grown on sapphire substrates

H. Tampo, A. Yamada, P. Fons, H. Shibata, K. Matsubara, K. Iwata, S. Niki, K. Nakahara, and H. Takasu

Appl. Phys. Lett. 84, 4412 (2004); http://dx.doi.org/10.1063/1.1758295 (3 pages) | Cited 27 times

Online Publication Date: 12 May 2004

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ZnO films were grown on low-temperature (LT) buffer layers on sapphire a-plane (11–20) substrates by radical source molecular-beam epitaxy. The LT buffer layers were found to effect the electrical properties of subsequently grown undoped ZnO films, and their presence was found to be indispensable for the growth of films with low carrier concentrations and high mobilities. Temperature-dependent Hall measurements showed the existence of a degenerate region related to the LT buffer layers. It was found that the effects of degenerate layers could be reduced by using annealing treatments and nitrogen doping of the LT buffer layers. The dominant residual donor energy of 110 meV was found to be different than previously reported. The carrier concentration of a ZnO film fabricated using a nitrogen-doped buffer layer was 7.5×1016 cm−3 with a mobility of 132 cm2/V s at room temperature. © 2004 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.61.Ga II-VI semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.A- Nucleation and growth
61.72.Cc Kinetics of defect formation and annealing
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In-plane and out-of-plane band-gap properties of a two-dimensional triangular polymer-based void channel photonic crystal

Guangyong Zhou, Michael James Ventura, Martin Straub, Min Gu, Atsushi Ono, Satoshi Kawata, Xuehua Wang, and Yuri Kivshar

Appl. Phys. Lett. 84, 4415 (2004); http://dx.doi.org/10.1063/1.1758298 (3 pages) | Cited 7 times

Online Publication Date: 12 May 2004

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The in-plane and out-of-plane band-gap properties of two-dimensional triangular void channel photonic crystals fabricated by femtosecond laser drilling in a solid polymer material were characterized for transverse electric (TE) and transverse magnetic (TM) polarization illumination. For a 24 layer structure stacked in the Γ–M direction, the fundamental stop gap resulted in the suppression of infrared transmission of as much as 96% for TE- and 85% for TM-polarized incident light. The midgap wavelength for the TM polarization was longer by 2.5% than that for the TE polarization. Increasing the angle of incidence for both the in-plane and out-of-plane cases shifted the stop gap to short wavelengths for both TE and TM polarizations. The experimental results allowed for the estimation of the cross section of void channels and the effective refractive index of the polymer after the fabrication. © 2004 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
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Electrostatic micromembrane actuator arrays as motion generator

X. T. Wu, J. Hui, M. Young, P. Kayatta, J. Wong, D. Kennith, J. Zhe, and C. Warde

Appl. Phys. Lett. 84, 4418 (2004); http://dx.doi.org/10.1063/1.1758299 (3 pages) | Cited 2 times

Online Publication Date: 12 May 2004

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A rigid-body motion generator based on an array of micromembrane actuators is described. Unlike previous microelectromechanical systems (MEMS) techniques, the architecture employs a large number (typically greater than 1000) of micron-sized (10–200 μm) membrane actuators to simultaneously generate the displacement of a large rigid body, such as a conventional optical mirror. For optical applications, the approach provides optical design freedom of MEMS mirrors by enabling large-aperture mirrors to be driven electrostatically by MEMS actuators. The micromembrane actuator arrays have been built using a stacked architecture similar to that employed in the Multiuser MEMS Process (MUMPS), and the motion transfer from the arrayed micron-sized actuators to macro-sized components was demonstrated. © 2004 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.79.Bh Lenses, prisms and mirrors
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.35.Np Adhesion
81.20.Vj Joining; welding
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Omnidirectional resonance in a metal–dielectric–metal geometry

Hocheol Shin, Mehmet Fatih Yanik, Shanhui Fan, Rashid Zia, and Mark L. Brongersma

Appl. Phys. Lett. 84, 4421 (2004); http://dx.doi.org/10.1063/1.1758306 (3 pages) | Cited 32 times

Online Publication Date: 12 May 2004

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We show that a planar metallic microcavity structure can exhibit an omnidirectional resonance, i.e., a resonance for which the resonance wavelength is independent of the incidence angle of light. The structure consists of a metal–dielectric–metal configuration. The omnidirectional resonance occurs when the reflection phase shift cancels the propagation shift. We numerically demonstrate such an omnidirectional resonance in an Ag–SiO2–Ag structure with realistic material parameters. Such omnidirectionally resonant structures are important for all-angle efficiency enhancement in light emitting diodes and photodetectors. © 2004 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.40.Rw Metal-insulator-metal structures
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Midinfrared difference frequency generation in quasi-phase matched diffusion bonded ZnSe plates

A. Mustelier, E. Rosencher, Ph. Kupecek, A. Godard, M. Baudrier, M. Lefebvre, M. Poulat, G. Mennerat, C. Pasquer, and Ph. Lemasson

Appl. Phys. Lett. 84, 4424 (2004); http://dx.doi.org/10.1063/1.1758771 (3 pages) | Cited 3 times

Online Publication Date: 12 May 2004

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We present the results on tunable midinfrared radiation (8–12 μm) generated in diffusion-bonded ZnSe slabs by difference frequency mixing of optical-parametric-oscillator output waves (≈2 μm). © 2004 American Institute of Physics.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
42.65.Yj Optical parametric oscillators and amplifiers
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Organic field-effect transistors with nonlithographically defined submicrometer channel length

Susanne Scheinert, Theodor Doll, Axel Scherer, Gernot Paasch, and Ingo Hörselmann

Appl. Phys. Lett. 84, 4427 (2004); http://dx.doi.org/10.1063/1.1758775 (3 pages) | Cited 20 times

Online Publication Date: 12 May 2004

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We developed an underetching technique to define submicrometer channel length polymer field-effect transistors. Short-channel effects are avoided by using thin silicon dioxide as gate insulator. The transistors with 1 and 0.74 μm channel length operate at a voltage as low as 5 V with a low inverse subthreshold slope of 0.4–0.5 V/dec, on–off ratio of 104, and without short-channel effects. The poly(3-alcylthiophene)’s still suffer from a low mobility and hysteresis does occur, but it is negligible for the drain voltage variation. With our underetching technique also device structures with self-aligned buried gate and channel length below 0.4 μm are fabricated on polymer substrates. © 2004 American Institute of Physics.
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85.30.Tv Field effect devices
85.65.+h Molecular electronic devices
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First-order quasi-phase-matched blue light generation in surface-poled Ti:indiffused lithium niobate waveguides

A. C. Busacca, C. L. Sones, R. W. Eason, and S. Mailis

Appl. Phys. Lett. 84, 4430 (2004); http://dx.doi.org/10.1063/1.1758776 (3 pages) | Cited 7 times

Online Publication Date: 12 May 2004

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We demonstrate efficient first-order quasi-phase-matched second-harmonic generation in a surface periodically poled Ti:indiffused lithium niobate waveguide; 6 mW of continuous-wave blue radiation (λ=412.6 nm) was produced showing the potential of surface domain inversion for efficient nonlinear waveguide interactions. © 2004 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.82.Et Waveguides, couplers, and arrays
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Resonant photoemission in Cr silicide at the absorption energy Cr 2p

L. Galán, M. García, J. M. Ripalda, I. Montero, E. Román, D. R. Batchelor, and P. R. Bressler

Appl. Phys. Lett. 84, 4433 (2004); http://dx.doi.org/10.1063/1.1758779 (3 pages)

Online Publication Date: 12 May 2004

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Valence band photoemission has been measured in chromium silicide as a function of the photon energy near the Cr 2p3/2 absorption threshold. Evidence of resonant photoemission is observed for the 3d valence band and the two-hole satellite. The threshold for normal Auger regime is 2.8 eV below the absorption peak and 0.8 eV below the Cr 2p3/2 binding energy, even lower than in pure Cr metal where it is already at extreme levels. The requirement for good resolution in photon energy relative to absorption width for the resonant Raman Auger to be observed is found to be less restrictive than expected. © 2004 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
71.20.Nr Semiconductor compounds
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