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15 Jun 2003

Volume 93, Issue 12, pp. 9429-10148

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Photonic crystal polarizers and polarizing beam splitters

D. R. Solli, C. F. McCormick, R. Y. Chiao, and J. M. Hickmann

J. Appl. Phys. 93, 9429 (2003); http://dx.doi.org/10.1063/1.1574174 (3 pages) | Cited 22 times

Online Publication Date: 30 May 2003

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We have experimentally demonstrated polarizers and polarizing beam splitters based on microwave-scale two-dimensional photonic crystals. Using polarized microwaves within certain frequency bands, we have observed a squared-sinusoid (Malus) transmission law when using the photonic crystal as a polarizer. The photonic crystal also functions as a polarizing beamsplitter; in this configuration it can be engineered to split incident polarizations in either order and in any direction, making it more versatile than conventional, Brewster-angle beamsplitters. © 2003 American Institute of Physics.
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42.79.Fm Reflectors, beam splitters, and deflectors
42.25.Ja Polarization
42.70.Qs Photonic bandgap materials

Photocurrents of 14 μm quantum-well infrared photodetectors

Y. Fu, M. Willander, J. Jiang, Ning Li, W. Lu, and H. C. Liu

J. Appl. Phys. 93, 9432 (2003); http://dx.doi.org/10.1063/1.1573342 (5 pages) | Cited 9 times

Online Publication Date: 30 May 2003

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We study the factors that determine photogenerated carriers and response wavelengths of photocurrents of long wavelength (∼14 μm) quantum well (QW) infrared photodetectors (QWIPs). The material structures of QWIPs are first characterized by the photoluminescence measurements (PL). By calculating the density of photogenerated carriers in the continuum above the energy barriers using the PL calibrated QWIP structures, we have demonstrated that due to the sample quality, the photocarriers can be either in miniband states (Bloch states in the multiple quantum wells), or they transport from one quantum well to the next in the form of running waves. By including possible scattering processes at the QWIP working temperature to link the theoretically calculated photocarrier density with the experimentally measured photocurrent, it is shown that the width of the photocurrent peaks of 14 μm GaAs/AlGaAs QWIPs under investigation is determined by the optical phonon emissions of photocarriers. We have further calculated the densities of photocarriers in the QWIPs reported in the literature. It is shown that the Bloch wave boundary conditions are appropriate for QWIPs with narrow QWs, whereas running wave boundary conditions are appropriate for wide QWs. © 2003 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Efficient KTiOPO4 blue-light converter for monochromatic 1.3188-μm emission line of pulsed Nd:YAG laser

Xiaodong Mu, Wei Shi, and Yujie J. Ding

J. Appl. Phys. 93, 9437 (2003); http://dx.doi.org/10.1063/1.1573339 (4 pages) | Cited 4 times

Online Publication Date: 30 May 2003

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A frequency converter is designed for producing efficient blue light at 0.4396 μm from a monochromatic, pulsed, 1.3188-μm Nd-doped emission line by quasi-phase-matched (QPM) second-harmonic generation (SHG), followed by sum-frequency generation, in an integrated, periodically poled KTiOPO4 (KTP) and monodomain KTP crystal. An average 55-mW (peak power of 43.0 W) blue light is achieved by us for an average 2.5-W (peak power of 2.0 kW) pump power; the overall conversion efficiency is thus 2.2%. Through polarization optimization, the same device produces an average 435 mW (peak power of 339.8 W) for the red light through QPM SHG, with a corresponding conversion efficiency of 16%. As a practical blue-light converter, the angle- and temperature-tuning characteristics and period tolerance have been fully investigated. © 2003 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters

Emission properties of PbO−Bi2O3−Ga2O3−GeO2 glasses doped with Tm3+ and Ho3+

Jay Hyok Song, Jong Heo, and Se Ho Park

J. Appl. Phys. 93, 9441 (2003); http://dx.doi.org/10.1063/1.1571968 (5 pages) | Cited 26 times

Online Publication Date: 30 May 2003

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Heavy metal oxide glasses containing GeO2 were investigated as potential hosts for 1.48 μm fiber-optic amplifiers because of their low phonon energy. Addition of ⩾10 mol % GeO2 to 0.57PbO−0.25Bi2O3−0.18Ga2O3 (mole fraction) glass provided thermal stability as well as good emission properties. The optimum glass composition for 1.48 μm amplifiers, considering lifetimes and population of the Tm3+:3H4 level, was 0.8 (0.57PbO−0.25Bi2O3−0.18Ga2O3)−0.2GeO2 (mole fraction). As the concentration of codoped Ho3+ exceeded 0.2 mol %, the population density of the Tm3+:3H4 level decreased sharply and the population inversion between the 3H4 and 3F4 levels in Tm3+ was achieved. © 2003 American Institute of Physics.
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78.55.Qr Amorphous materials; glasses and other disordered solids
63.50.-x Vibrational states in disordered systems
42.70.Ce Glasses, quartz

Spectroscopic characterization of 1450 nm semiconductor pump laser structures for Raman amplifiers

S. B. Constant, S. Tomić, D. Lock, T. E. Sale, S. J. Sweeney, and T. J. C. Hosea

J. Appl. Phys. 93, 9446 (2003); http://dx.doi.org/10.1063/1.1575499 (10 pages) | Cited 2 times

Online Publication Date: 30 May 2003

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In order to characterize various different epilayer designs for semiconductor Raman amplifier pump lasers, combined electromodulated reflectance (ER) and photoluminescence (PL) studies were performed on wafer samples of InP / InGaAsP / InGaAsP edge-emitter laser structures in the infrared spectral region. Information about the quantum well (QW) transitions is obtained primarily from the ER, with additional corroboration provided by the PL. The ER spectra are fitted with a line shape model to obtain the ground-state and higher-order QW transition energies, which are found to agree well with theoretically calculated values. The ER spectra also provide the waveguide core and barrier compositions and built-in electric fields in the laser structures. The information provided by ER studies on the prefabrication wafers is found to corroborate well with diagnostic spontaneous emission measurements performed on actual laser devices fabricated from the same wafer batches. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
78.67.De Quantum wells
78.20.Jq Electro-optical effects
78.30.Fs III-V and II-VI semiconductors

Ultraviolet-light-induced near-infrared photorefractivity and two-color holography in highly Mg-doped LiNbO3

Guoquan Zhang and Yasuo Tomita

J. Appl. Phys. 93, 9456 (2003); http://dx.doi.org/10.1063/1.1577818 (4 pages) | Cited 2 times

Online Publication Date: 30 May 2003

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We investigate the ultraviolet (UV)-light-induced transient photorefractivity in a highly Mg-doped LiNbO3 crystal. The thermal activation energy of the UV-light-induced defect centers responsible for the induced transient photorefractivity was measured to be 0.65 eV and holes were found to be the major charge carriers. These results provide a solid basis for the model that intermediate states O− are the UV-light-induced defect centers in the crystal. We also demonstrate quasinondestructive two-color holography using UV-light-induced transient photorefractivity. The two-color recording sensitivity was measured to be as high as 0.05 cm/J with a recording intensity of 5 W/cm2 at 780 nm and a gating intensity of 0.47 W/cm2 at 365 nm. © 2003 American Institute of Physics.
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42.70.Ln Holographic recording materials; optical storage media
42.40.Ht Hologram recording and readout methods
42.40.Lx Diffraction efficiency, resolution, and other hologram characteristics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
71.55.Ht Other nonmetals
61.82.Ms Insulators

Optical transitions and upconversion properties of Ho3+ doped ZnO−TeO2 glass

J. C. Boyer, F. Vetrone, J. A. Capobianco, A. Speghini, and M. Bettinelli

J. Appl. Phys. 93, 9460 (2003); http://dx.doi.org/10.1063/1.1577817 (6 pages) | Cited 19 times

Online Publication Date: 30 May 2003

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Optical absorption, luminescence spectra and upconversion of both red to green and infrared to green luminescence have been studied for a Ho3+ doped zinc tellurite glass of composition 19ZnO−80TeO2−1Ho2O3. From the absorption data, Judd–Ofelt parameters for the Ho3+ ion are calculated along with the radiative transition rates, branching ratios and radiative lifetimes of the major Ho3+ emitting levels. The upconversion luminescence for both 646 and 754 nm excitation was attributed to a two photon excited state absorption upconversion mechanism that occurs via the 5I7 level. For an excitation power density of 610 W/cm2 an upconversion efficiency of 1.22% was determined for the case of 646 nm excitation, which is considerably higher than what has been reported in Ho3+ doped fluoride single crystals. Under 754 nm excitation, an upconversion efficiency of 0.27% was observed for a excitation power density of 610 W/cm2, which is reasonably low compared to other Ho3+ doped materials. © 2003 American Institute of Physics.
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78.55.Qr Amorphous materials; glasses and other disordered solids
78.40.Pg Disordered solids

Light-induced absorption in photorefractive BaTiO3 crystals

Ravinder Kumar Banyal and B. Raghavendra Prasad

J. Appl. Phys. 93, 9466 (2003); http://dx.doi.org/10.1063/1.1578533 (4 pages) | Cited 1 time

Online Publication Date: 30 May 2003

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We present the experimental results on the measurement of temporal and steady-state light-induced absorption change in undoped and rhodium-doped barium titanate (Rh:BaTiO3) crystals at different wavelengths and intensities. Theoretical calculations based on a two-center charge transport model agree well with the experimental results which supplement the earlier studies carried out using photorefractive BaTiO3 crystals. We also report a wavelength-specific light-induced effect that modifies the absorption dynamics in a peculiar manner. This can be attributed to light-induced thermal effects. However, the possibility of additional photorefractive centers becoming active cannot be ruled out. © 2003 American Institute of Physics.
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78.20.-e Optical properties of bulk materials and thin films
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
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Laser-guided, intersecting discharge channels for the final beam transport in heavy-ion fusion

C. Niemann, S. Neff, A. Tauschwitz, D. Penache, R. Birkner, C. Constantin, R. Knobloch, R. Presura, F. B. Rosmej, D. H. H. Hoffmann, and S. S. Yu

J. Appl. Phys. 93, 9470 (2003); http://dx.doi.org/10.1063/1.1569395 (7 pages) | Cited 2 times

Online Publication Date: 30 May 2003

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Ion-beam transport in space charge neutralizing discharge channels has been proposed for the final focus and chamber transport in a heavy-ion fusion reactor. A driver scenario with two-sided target illumination requires a system of two intersecting discharges to transport beams of the same charge from opposite sides towards the fusion target. In this article we report on experiments on the creation of free-standing, intersecting high-current discharge channels. The discharges are initiated in ammonia gas (NH3) in a metallic chamber by two perpendicular CO2-laser beams, which resonantly heat and subsequently rarefy the gas along the laser paths before the breakdown. These low density channels guide the discharges along the predefined paths and also around the 90° angles without any mechanical guiding structures. In this way stable X-, T-, and L-shaped discharges with currents in excess of 40 kA, at pressures of a few mbar were created with a total length of 110 cm. An 11.4 A MeV 58Ni+12 beam from the UNILAC (Universal Linear Accelerator) linear accelerator was used to probe the line-integrated ion-optical properties of the central channel in a T-shaped discharge. © 2003 American Institute of Physics.
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28.52.Av Theory, design, and computerized simulation
52.80.-s Electric discharges
07.77.-n Atomic, molecular, and charged-particle sources and detectors
52.40.Mj Particle beam interactions in plasmas

Characteristics of hard x-ray emission from laser-induced vacuum spark discharges

Akira Ohzu and Kazunori Ito

J. Appl. Phys. 93, 9477 (2003); http://dx.doi.org/10.1063/1.1572546 (6 pages) | Cited 1 time

Online Publication Date: 30 May 2003

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An experimental study of the characteristics of hard x-ray emission in laser-induced vacuum spark discharges has been carried out. The spark discharge is performed in a gap (10 mm) of pin electrodes using a Marx generator and a laser pulse to produce Au plasma on the tip of an anode. When spark discharge with charge voltage of 150 kV occurred simultaneously with the incidence of a laser pulse, an x-ray pulse made of a short (∼20 ns) x-ray spike pulse and a long (∼400 ns) pulse was emitted with high intensity (∼10 mR per shot). The two pulses appeared at the beginning and at the latter part of discharge. The effective photon energy was around 150 and 80 keV, respectively. The results show that the x-ray intensity strongly depends on the timing of the onset of the discharge with respect to the laser irradiation, the laser intensity, and the charge voltage. The mechanisms responsible for the x-ray emission are discussed in terms of the results observed. © 2003 American Institute of Physics.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Vp Discharge in vacuum
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.59.Px Hard X-ray sources

Abatement of perfluorinated compounds using microwave plasmas at atmospheric pressure

Y. Kabouzi, M. Moisan, J. C. Rostaing, C. Trassy, D. Guérin, D. Kéroack, and Z. Zakrzewski

J. Appl. Phys. 93, 9483 (2003); http://dx.doi.org/10.1063/1.1574595 (14 pages) | Cited 26 times

Online Publication Date: 30 May 2003

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Microwave plasmas sustained at atmospheric pressure, for instance by electromagnetic surface waves, can be efficiently used to abate greenhouse-effect gases such as perfluorinated compounds. As a working example, we study the destruction and removal efficiency (DRE) of SF6 at concentrations ranging from 0.1% to 2.4% of the total gas flow where N2, utilized as a purge gas, is the carrier gas. O2 is added to the mixture at a fixed ratio of 1.2–1.5 times the concentration of SF6 to ensure full oxidation of the SF6 fragments, providing thereby scrubbable by-products. Fourier-transform infrared spectroscopy has been utilized for identification of the by-products and quantification of the residual concentration of SF6. Optical emission spectroscopy was employed to determine the gas temperature of the nitrogen plasma. In terms of operating parameters, the DRE is found to increase with increasing microwave power and decrease with increasing gas flow rate and discharge tube radius. Increasing the microwave power, in the case of a surface-wave discharge, or decreasing the gas flow rate increases the residence time of the molecules to be processed, hence, the observed DRE increase. In contrast, increasing the tube radius or the gas-flow rate increases the degree of radial contraction of the discharge and, therefore, the plasma-free space close to the tube wall: this comparatively colder region favors the reformation of the fragmented SF6 molecules, and enlarging it lowers the destruction rate. DRE values higher than 95% have been achieved at a microwave power of 6 kW with 2.4% SF6 in N2 flow rates up to 30 standard l/min. © 2003 American Institute of Physics.
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52.77.-j Plasma applications
52.80.Pi High-frequency and RF discharges
07.88.+y Instruments for environmental pollution measurements
89.60.-k Environmental studies
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.80.Gk Analytical methods involving vibrational spectroscopy
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

The CN free radical in acetonitrile discharges

Peng Li and Wai Yip Fan

J. Appl. Phys. 93, 9497 (2003); http://dx.doi.org/10.1063/1.1575928 (6 pages) | Cited 3 times

Online Publication Date: 30 May 2003

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Infrared diode laser absorption, Fourier-transform infrared (FTIR) and optical emission spectroscopies have been applied to the study of the CN radical and other transient species in acetonitrile/argon plasmas. A dc discharge was used to produce the CN radical in which both the infrared rovibrational spectrum around 2000 cm−1 and the B−X electronic emission spectrum around 388 nm were detected. The concentration of CN was determined to be in the region of 1011–1012 cm−3, aided by vibrational intensity calculations performed at UB3LYP/6−311+G∗∗ level of theory in Gaussian 98. An acetonitrile plasma was also generated in a static cell and by using FTIR spectroscopy; the main product observed under such conditions was HCN. Based on the experimental data, it appears that the major reaction pathways for CN in the plasma involve electron impact dissociation and excitation processes and its reaction with HCN. In order to provide a better overall understanding of the gas phase reaction pathways in the plasma, emission studies of excited NH, C2 and CH generated in the same plasma were performed as well. © 2003 American Institute of Physics.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
34.80.Gs Molecular excitation and ionization
82.80.Gk Analytical methods involving vibrational spectroscopy

Radio frequency magnetron sputtering deposition of calcium phosphate coatings: The effect of resputtering on the coating composition

B. Feddes, J. G. C. Wolke, J. A. Jansen, and A. M. Vredenberg

J. Appl. Phys. 93, 9503 (2003); http://dx.doi.org/10.1063/1.1576894 (5 pages) | Cited 6 times

Online Publication Date: 30 May 2003

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Radio frequency magnetron plasma sputtering deposition is a fairly complex deposition method. Deposition of the film is influenced by the energetic bombardment of several species, like energetic electrons, neutrals, ions from the sputtering target and the plasma, and ultraviolet light. In this work we study the origin and the degree of (preferential) resputtering of species from a calcium phosphate ceramic film during the deposition process. We found that negatively charged oxygen is mostly responsible for the resputtering phenomena that occur. The degree of resputtering was determined by comparing the amount of material deposited behind and at the position of an aperture, which was positioned between the sputtering target and the substrate. The degree of resputtering can be derived, because the material behind the aperture is almost completely protected from bombardment by negatively charged oxygen. We found that at low Ar pressure, more than half of the material deposited is resputtered, preferentially P. Resputtering of the coating decreases with an increase in Ar pressure. An explanation for this may be that more negatively charged, energetic oxygen is ejected from the target at low Ar pressure, while at high Ar pressure more neutral, less energetic, oxygen is ejected. The former gives a higher resputtering rate. © 2003 American Institute of Physics.
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68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering

Model of a He–Xe low-pressure dc positive column plasma

S. Gortchakov, H. Lange, and D. Uhrlandt

J. Appl. Phys. 93, 9508 (2003); http://dx.doi.org/10.1063/1.1576901 (8 pages) | Cited 21 times

Online Publication Date: 30 May 2003

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The positive column plasma of dc glow discharges at low pressure in a mixture of helium and 2% xenon is studied. Such glow discharges are favored candidates for the design of mercury-free light sources. A self-consistent model of the column plasma is presented based on strict radially resolved treatment of the nonlocal non-equilibrium kinetics of the electron component, the space-charge potential and the densities of ions and excited atom states. A detailed reaction kinetic scheme of the low-lying xenon excited states has been developed and is included in the model. The model is validated by a comparison with measurements of the axial electric field and the densities of the lowest metastable and resonant xenon levels. The latter was obtained by tunable diode laser absorption and probe diagnostics. The initial results of the model show a pronounced radial structure of the rare-gas column plasma and nonlocal properties of the electron power budget caused by space-charge confinement. The impact of the uncertainty of atomic data used in the model on the quantitative results is investigated in detail. A large impact of the cross sections of electron-impact excitation of the xenon ground state and the excitation and ionization of the xenon excited states, which are known with insufficient reliability only, has been observed. © 2003 American Institute of Physics.
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52.80.Hc Glow; corona
52.65.-y Plasma simulation
31.50.Df Potential energy surfaces for excited electronic states
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.25.-b Plasma properties
31.50.Bc Potential energy surfaces for ground electronic states
52.20.-j Elementary processes in plasmas
34.80.Dp Atomic excitation and ionization
82.20.-w Chemical kinetics and dynamics

Three-dimensional self-consistent radiation transport model for the fluid simulation of plasma display panel cell

H. C. Kim, S. S. Yang, and J. K. Lee

J. Appl. Phys. 93, 9516 (2003); http://dx.doi.org/10.1063/1.1577399 (7 pages) | Cited 11 times

Online Publication Date: 30 May 2003

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In plasma display panels (PDPs), the resonance radiation trapping is one of the important processes. In order to incorporate this effect in a PDP cell, a three-dimensional radiation transport model is self-consistently coupled with a fluid simulation. This model is compared with the conventional trapping factor method in gas mixtures of neon and xenon. It shows the differences in the time evolutions of spatial profile and the total number of resonant excited states, especially in the afterglow. The generation rates of UV light are also compared for the two methods. The visible photon flux reaching the output window from the phosphor layers as well as the total UV photon flux arriving at the phosphor layer from the plasma region are calculated for resonant and nonresonant excited species. From these calculations, the time-averaged spatial profiles of the UV flux on the phosphor layers and the visible photon flux through the output window are obtained. Finally, the diagram of the energy efficiency and the contribution of each UV light are shown. © 2003 American Institute of Physics.
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52.75.-d Plasma devices
85.60.Pg Display systems
52.65.Kj Magnetohydrodynamic and fluid equation
42.72.Bj Visible and ultraviolet sources
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Relation between the molecular orientation of a liquid crystal monolayer and the underlying polyimide film exposed to linearly polarized ultraviolet light

Kiyoaki Usami, Kenji Sakamoto, and Sukekatsu Ushioda

J. Appl. Phys. 93, 9523 (2003); http://dx.doi.org/10.1063/1.1572548 (6 pages) | Cited 4 times

Online Publication Date: 30 May 2003

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We have determined the relation between the in-plane anisotropy of the molecular orientation of a liquid crystal (LC) monolayer and the underlying polyimide film exposed to linearly polarized ultraviolet light (LPUVL). To evaluate the anisotropy of the LC monolayer and the polyimide film, the sample orientation dependence of the polarized infrared absorption spectrum was measured. The in-plane anisotropy of the LC monolayer was found to be proportional to that of the polyimide film, the proportionality factor being about 75%. This result strongly suggests that the alignment of the LC molecules in contact with the LPUVL-exposed polyimide film is induced by an interaction between the polyimide and LC molecules. © 2003 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures

Laser-induced decompression shock development in fused silica

Junlan Wang, Richard L. Weaver, and Nancy R. Sottos

J. Appl. Phys. 93, 9529 (2003); http://dx.doi.org/10.1063/1.1574175 (8 pages) | Cited 9 times

Online Publication Date: 30 May 2003

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Laser-induced weak shock formation in fused silica is studied using standard wave mechanics and applied to thin-film laser spallation experiments. Due to the negative nonlinear elasticity of fused silica, a laser-induced Gaussian stress pulse evolves into a shock after traveling a certain distance in a fused silica substrate. Experimental observations confirm theoretical predictions of shock development. A decompression shock forms and greatly enhances interfacial failure of a thin film deposited on the substrate. The effects of laser fluence and substrate thickness (attenuation) on shock development are also investigated. © 2003 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
79.20.Ds Laser-beam impact phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators

Spectroscopic ellipsometry of thin film and bulk anatase (TiO2)

G. E. Jellison, L. A. Boatner, J. D. Budai, B.-S. Jeong, and D. P. Norton

J. Appl. Phys. 93, 9537 (2003); http://dx.doi.org/10.1063/1.1573737 (5 pages) | Cited 45 times

Online Publication Date: 30 May 2003

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Spectroscopic ellipsometry (SE) measurements were made on thin-film and single-crystal TiO2 anatase using a two-modulator generalized ellipsometer. The TiO2 films were epitaxially stabilized on a LaAlO3 substrate in the anatase crystal structure using reactive sputter deposition. The films were highly crystalline, possessing a “stepped surface” morphology indicative of atomic layer-by-layer growth. The SE results for the anatase film indicate that the material is essentially oriented with the c axis perpendicular to the substrate, but there is some anisotropy near the interface and the surface. Corrugations of the film surface, as observed using atomic force microscopy, are consistent with a surface structure needed to create cross polarization. Accurate values of the optical functions of crystalline anatase were obtained above and below the band edge using SE. Above the band edge, both the ordinary and extraordinary complex dielectric functions exhibited two critical points. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Nk Insulators
77.55.-g Dielectric thin films
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
07.60.Fs Polarimeters and ellipsometers
61.66.Fn Inorganic compounds
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Micro-Raman study of electronic properties of inversion domains in GaN-based lateral polarity heterostructures

M. Park, J. J. Cuomo, B. J. Rodriguez, W.-C. Yang, R. J. Nemanich, and O. Ambacher

J. Appl. Phys. 93, 9542 (2003); http://dx.doi.org/10.1063/1.1570507 (6 pages) | Cited 14 times

Online Publication Date: 30 May 2003

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The electronic properties of inversion domains in a GaN-based lateral polarity heterostructure were investigated using micro-Raman spectroscopy. The piezoelectric polarization of each domain was calculated from strain determined via Raman scattering. The free carrier concentration and electron mobility were deduced from the longitudinal optical phonon–plasmon coupled mode. The electron concentration in the N-face domain was slightly higher than that in the Ga-face domain. It appears that during growth, a larger number of donor impurities may have been incorporated into the N-face domain than into the Ga-face domain. © 2003 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
77.65.-j Piezoelectricity and electromechanical effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Ej Polarization and depolarization
73.50.Dn Low-field transport and mobility; piezoresistance
63.20.kk Phonon interactions with other quasiparticles
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Imaging subwavelength holes using an apertureless near-field scanning optical microscope

F. Formanek, Y. De Wilde, and L. Aigouy

J. Appl. Phys. 93, 9548 (2003); http://dx.doi.org/10.1063/1.1574178 (5 pages) | Cited 10 times

Online Publication Date: 30 May 2003

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We present investigations of the light scattered by subwavelength holes in a chromium film using an apertureless near-field scanning optical microscope, which operates either in the visible (λ=655 nm) or in the infrared (λ=10.6 μm). The near-field optical images exhibit patterns around the holes that seem to coincide with the component of the stray electrical field parallel to the tip axis. A tip–sample dipole coupling model provides a satisfactory description of the experimental data recorded in the infrared with light polarized normally to the sample surface. © 2003 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.37.Uv Near-field scanning microscopy and spectroscopy
78.66.Bz Metals and metallic alloys
07.79.Fc Near-field scanning optical microscopes

Physical and optical properties of sol-gel nano-silver doped silica film on glass substrate as a function of heat-treatment temperature

Wenyan Li, Sudipta Seal, Edward Megan, Jeff Ramsdell, Kirk Scammon, Gerald Lelong, Laurent Lachal, and Kathleen A. Richardson

J. Appl. Phys. 93, 9553 (2003); http://dx.doi.org/10.1063/1.1571215 (9 pages) | Cited 61 times

Online Publication Date: 30 May 2003

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Nano-silver doped silica films were deposited on glass slides using a sol-gel process and heat-treated at different temperatures. The films were characterized by ultraviolet-visible spectroscopy, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy for their optical, chemical, and structural properties. The absorption peak of silver colloids (wavelength from 400 to 460 nm) was present and a blueshift and intensity reduction of the absorption peak was observed during heat-treatment. Particle size reduction and surface morphology changes in the films were observed by AFM as a function of varying heat treatment temperatures. Silver nanoparticles were formed through spontaneous reduction of silver ions. The oxidation of silver occurs during heat-treatment, causing a reduction of absorption intensity. An interdiffusion between the Ag in the film and Na in the substrate glass was observed by XPS and RBS. Sodium in the coating likely increased the stability of silver oxide at high temperature treated samples. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
78.66.Sq Composite materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.40.Ha Other nonmetallic inorganics
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Ps Atomic force microscopy (AFM)
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
68.37.Lp Transmission electron microscopy (TEM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Wigner function modeling of quantum well semiconductor lasers using classical electromagnetic field coupling

Philip Weetman and Marek S. Wartak

J. Appl. Phys. 93, 9562 (2003); http://dx.doi.org/10.1063/1.1574180 (14 pages) | Cited 3 times

Online Publication Date: 30 May 2003

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A model of the quantum well laser is formulated using Wigner functions whose evolution is governed by the quantum Boltzmann equations. This model incorporates the heterostructure potential and electromagnetic interactions using a classical field approximation, scattering processes by simple Boltzmann scattering, and spontaneous emission by quantum Langevin theory. The quantum Boltzmann equations are derived from Heisenberg’s equation of motion and then simplified for practical purposes. Calculations are performed for a simplified test system in the steady state in order to illustrate some numerical techniques as well as results that can be obtained. Results shown are for the electron and hole densities and the self-consistent heterostructure potential with and without electromagnetic coupling, the output power versus energy, and the electron and hole currents versus position for two applied bias potentials. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Effect of liner thickness on electromigration lifetime

E. G. Liniger, C. -K. Hu, L. M. Gignac, and A. Simon

J. Appl. Phys. 93, 9576 (2003); http://dx.doi.org/10.1063/1.1575497 (7 pages) | Cited 15 times

Online Publication Date: 30 May 2003

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Electromigration lifetime was measured as a function of liner thickness for Cu/SiO2 interconnect structures. A significant increase in mean lifetime was observed for structures in which the liner thickness at the base of the test via was less than approximately 6 nm, with a current density <5 mA/μm2 in the power line connected to the test via. This is attributed to the continuous flow of Cu across the thin and possibly discontinuous liner at the base of the via. For extremely thin liner coverage, <1.4 nm at the base of the via and 2.5 at the bottom of the test line, the mean lifetime was observed to decrease as a rapid diffusion path was created which partially offset the beneficial effects of continuous flow. Failure distributions appeared to be trimodal and this was confirmed through failure analysis. In the case of thin liner coverage (<6 nm), early fails, which are typically characterized by slitlike voids at the via/line interface, were not observed. © 2003 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
66.30.Qa Electromigration
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Annealing-induced Ge/Si(100) island evolution

Yangting Zhang and Jeff Drucker

J. Appl. Phys. 93, 9583 (2003); http://dx.doi.org/10.1063/1.1575914 (8 pages) | Cited 15 times

Online Publication Date: 30 May 2003

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Ge/Si(100) islands were found to coarsen during in situ annealing at growth temperature. Islands were grown by molecular-beam epitaxy of pure Ge and annealed at substrate temperatures of T=450, 550, 600, and 650 °C, with Ge coverages of 6.5, 8.0, and 9.5 monolayers. Three coarsening mechanisms operate in this temperature range: wetting-layer consumption, conventional Ostwald ripening, and Si interdiffusion. For samples grown and annealed at T=450 °C, consumption of a metastably thick wetting layer causes rapid initial coarsening. Slower coarsening at longer annealing times occurs by conventional Ostwald ripening. Coarsening of samples grown and annealed at T=550 °C occurs via a combination of Si interdiffusion and conventional Ostwald ripening. For samples grown and annealed at T⩾600 °C, Ostwald ripening of SiGe alloy clusters appears to be the dominant coarsening mechanism. © 2003 American Institute of Physics.
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68.55.Nq Composition and phase identification
61.72.Cc Kinetics of defect formation and annealing
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Cy Elemental semiconductors
68.35.Fx Diffusion; interface formation

Growth diagram and morphologies of AlN thin films grown by molecular beam epitaxy

G. Koblmueller, R. Averbeck, L. Geelhaar, H. Riechert, W. Hösler, and P. Pongratz

J. Appl. Phys. 93, 9591 (2003); http://dx.doi.org/10.1063/1.1575929 (6 pages) | Cited 38 times

Online Publication Date: 30 May 2003

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A growth diagram for molecular beam epitaxy of AlN on sapphire and 6H–SiC was established using reflection high energy electron diffraction, atomic force microscopy, and Rutherford backscattering spectrometry. In varying the Al/N ratio and growth temperature, distinctive surface morphologies emerge, which are assigned to three regimes of growth, one N-rich (Al/N<1) and two Al-rich (Al/N>1) regimes. Under N-rich conditions, AlN films exhibit rough surface morphologies. In contrast, Al-rich conditions produce excellent smooth surface morphologies, but with the constraint of Al droplet formation at very high Al/N ratios and low temperatures. The differentiation between N-rich and Al-rich regimes is given only by the Al/N ratio, while the two Al-rich regimes (intermediate self-regulated and droplet regime) are separated by the boundary line of Al droplet formation. For this boundary an Arrhenius dependence of growth temperature was found, yielding an activation energy of 3.4±0.1 eV. The observed morphology transitions are attributed to varying surface adatom mobilities present under the different Al/N ratios. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation
68.37.Ps Atomic force microscopy (AFM)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
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