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15 Dec 2006

Volume 100, Issue 12, Articles (12xxxx)

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Spatial distribution of deep level defects in crack-free AlGaN grown on GaN with a high-temperature AlN interlayer

Q. Sun, H. Wang, D. S. Jiang, R. Q. Jin, Y. Huang, S. M. Zhang, H. Yang, U. Jahn, and K. H. Ploog

J. Appl. Phys. 100, 123101 (2006); http://dx.doi.org/10.1063/1.2402964 (5 pages) | Cited 5 times

Online Publication Date: 19 December 2006

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The deep level luminescence of crack-free Al0.25Ga0.75N layers grown on a GaN template with a high-temperature grown AlN interlayer has been studied using spatially resolved cathodoluminescence (CL) spectroscopy. The CL spectra of Al0.25Ga0.75N grown on a thin AlN interlayer present a deep level aquamarine luminescence (DLAL) band at about 2.6 eV and a deep level violet luminescence (DLVL) band at about 3.17 eV. Cross-section line scan CL measurements on a cleaved sample edge clearly reveal different distributions of DLAL-related and DLVL-related defects in AlGaN along the growth direction. The DLAL band of AlGaN is attributed to evolve from the yellow luminescence band of GaN, and therefore has an analogous origin of a radiative transition between a shallow donor and a deep acceptor. The DLVL band is correlated with defects distributed near the GaN/AlN/AlGaN interfaces. Additionally, the lateral distribution of the intensity of the DLAL band shows a domainlike feature which is accompanied by a lateral phase separation of Al composition. Such a distribution of deep level defects is probably caused by the strain field within the domains.
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78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

Photoluminescence study of ZnO films codoped with nitrogen and tellurium

H. L. Porter, J. F. Muth, J. Narayan, John V. Foreman, and Henry O. Everitt

J. Appl. Phys. 100, 123102 (2006); http://dx.doi.org/10.1063/1.2372312 (4 pages) | Cited 5 times

Online Publication Date: 20 December 2006

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Epitaxial ZnO films codoped with tellurium and nitrogen were grown by pulsed laser deposition on c-axis oriented sapphire substrates. The codoping strategy allowed the resistivity of the films to be controlled over several orders of magnitude and may prove useful in the development of ZnO based light emitters. Photoluminescence studies of tellurium-doped, nitrogen-doped, tellurium and nitrogen codoped, and undoped ZnO films were conducted. Strong room temperature photoluminescence and stimulated emission were observed in the undoped and Te-doped films, but not in codoped films. Time-resolved photoluminescence measurements indicated that carrier lifetime was significantly reduced in doped ZnO as compared to undoped ZnO.
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81.05.Dz II-VI semiconductors
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors
78.55.Et II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics

Evaluation of the OH− influence on visible and near-infrared quantum efficiencies of Tm3+ and Yb3+ codoped sodium aluminophoshate glasses

Idelma A. A. Terra, Andrea S. S. de Camargo, Luiz Antonio de O. Nunes, Renê A. Carvalho, and Máximo Siu Li

J. Appl. Phys. 100, 123103 (2006); http://dx.doi.org/10.1063/1.2400510 (8 pages) | Cited 5 times

Online Publication Date: 20 December 2006

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This paper presents a throughout spectroscopic investigation of Yb3+/Tm3+ codoped sodium aluminophosphate glasses in the visible and near-infrared spectral regions. Two sets of samples, prepared in air and nitrogen atmospheres, were characterized by transmission, absorption, luminescence, excited state lifetimes, and upconversion. The data are discussed in terms of OH− contents in the samples, and their influence on Tm3+ fluorescence quantum efficiencies. Besides, a theoretical analysis of radiative properties, by the Judd-Ofelt [ Phys. Rev. 127, 750 (1962) ]; J. Chem. Phys. 37, 511 (1962) ] theory, is also presented in comparison to experimental data. Results indicate that samples prepared in N2 atmosphere, with lower OH− content, present superior properties than those prepared in air. Among these properties are a 30% more extensive infrared transmission of the host matrix, higher emission intensities, and decreased quenching effects, characterizing them as potential materials for high power laser generation, as well as efficient upconversion.
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42.70.Ce Glasses, quartz
78.40.Pg Disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.55.Qr Amorphous materials; glasses and other disordered solids

Mode-conversion enhancement of guided optical waves by magnetostatic surface waves propagating collinearly in obliquely magnetized bismuth-doped yttrium-iron-garnet film waveguide

Bao-Jian Wu, Feng Wen, and Kun Qiu

J. Appl. Phys. 100, 123104 (2006); http://dx.doi.org/10.1063/1.2399883 (5 pages) | Cited 1 time

Online Publication Date: 22 December 2006

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The dispersion formula and dynamic magnetization for magnetostatic surface waves (MSSWs) under arbitrarily inclined bias magnetic field and the mode-conversion effect of guided optical waves (GOWs) by the MSSWs propagating collinearly in obliquely magnetized bismuth-doped yttrium-iron-garnet film waveguide are studied theoretically. It is shown by our calculation that: (1) by optimizing the direction of bias magnetic field, the mode-conversion efficiency (MCE) of the GOWs can be increased by about 7.3 dB compared with that at the conventional magnetization; (2) at in-plane magnetization, the coupling interaction between the incident light and the frequency-shifted and mode-converted light is so strong that the others can be neglected, and thus the analysis on the GOW mode-conversion with the MSSWs in the case can be simplified further; and (3) under the optimum condition, the linearly dynamic dependence of the mode-conversion and diffraction efficiency on the microwave current is up to 25 dB or so, and the first peak value is 62.7%.
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78.20.Ls Magneto-optical effects
75.30.Ds Spin waves
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
42.79.Gn Optical waveguides and couplers
75.50.Gg Ferrimagnetics

Coupling characteristics of surface modes in truncated two-dimensional photonic crystals

Hyoung-Gyu Choi, Sang Soon Oh, Sun-Gu Lee, Myeong-Woo Kim, Jae-Eun Kim, Hae Yong Park, and Chul-Sik Kee

J. Appl. Phys. 100, 123105 (2006); http://dx.doi.org/10.1063/1.2401282 (4 pages) | Cited 4 times

Online Publication Date: 22 December 2006

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We investigate the coupling properties of localized modes between two identical truncated triangular photonic crystals composed of air holes in a dielectric background. The frequency of even parity modes varies more sensitively to the distance between the truncated faces of the crystals; i.e., the coupling distance. This behavior is explained in terms of photonic bands and spatial distribution of fields. This localized mode with even parity is shown to be a good guided mode from the finite-difference time-domain simulation. The guided range can be tuned by varying the coupling distance and the degree of truncation.
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42.70.Qs Photonic bandgap materials
63.20.Pw Localized modes

Optical absorption intensity analysis and emission cross sections for the intermanifold and the inter-Stark transitions of Nd3+(4f 3) in polycrystalline ceramic Y2O3

Dhiraj K. Sardar, Douglas M. Dee, Kelly L. Nash, Raylon M. Yow, and John B. Gruber

J. Appl. Phys. 100, 123106 (2006); http://dx.doi.org/10.1063/1.2402970 (7 pages) | Cited 10 times

Online Publication Date: 26 December 2006

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Spectroscopic properties have been characterized for trivalent neodymium doped polycrystalline ceramic ytttria, Nd3+:Y2O3. The Judd-Ofelt [Phys. Rev. 127, 750 (1962); J. Chem. Phys. 37, 511 (1962) ] analysis has been applied to the room temperature absorption spectrum to determine the radiative decay rates and branching ratios of Nd3+ transitions from the math metastable manifold to the math lower-lying multiplet manifolds. The quantum efficiency is determined from the measured fluorescence lifetime and the radiative lifetime of the math manifold state. In addition, a detailed characterization of the Stark energy levels of the math and math manifolds has been performed using the room temperature fluorescence spectra for the math→math and math→math transitions of Nd3+(4f3) in ceramic Y2O3. The emission cross sections of the math→math and math→math intermanifold transitions have been determined. Also, the peak emission cross sections of the principal inter-Stark peak transitions R1→X5 and R1→Y2 have been determined. Finally, the spectroscopic properties of ceramic Nd3+:Y2O3 are compared with those of ceramic Nd3+:YAG as well as single crystals of Nd3+:Y2O3 and Nd3+:YAG.
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42.70.Hj Laser materials
78.20.Jq Electro-optical effects
78.55.Hx Other solid inorganic materials
42.55.Rz Doped-insulator lasers and other solid state lasers
78.40.Ha Other nonmetallic inorganics

Band gap gratings using quantum well intermixing for quasi-phase-matching

A. S. Helmy, A. C. Bryce, D. C. Hutchings, J. S. Aitchison, and J. H. Marsh

J. Appl. Phys. 100, 123107 (2006); http://dx.doi.org/10.1063/1.2402034 (8 pages) | Cited 3 times

Online Publication Date: 27 December 2006

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In this work, the spatial resolution of two quantum well intermixing processes has been obtained using spatially resolved photoluminescence. The processes investigated are impurity-free vacancy disordering using SiO2/SiO2:P caps and sputtered silica induced intermixing. These studies aimed to choose a suitable intermixing technology to realize the band gap gratings for domain disordering quasi-phase-matching in GaAs/AlGaAs heterostructures. From the photoluminescence studies it was established that the process of impurity-free vacancy disordering using SiO2/SiO2:P caps has a spatial resolution on the order of 7 μm, while the process of sputtered silica induced intermixing has a spatial resolution on the order of 3 μm. From these measurements it was demonstrated that the sputtered silica induced intermixing process is more suitable for the fabrication of the gratings needed for quasi-phase-matching in the samples studied here. Successful quasi-phase-matching demonstrated through second harmonic generation at 775 nm has been produced in GaAs/AlAs short superlattice waveguides using sputtered silica induced intermixing through domain disordering quasi-phase-matching. The gratings have shown a duty cycle far from the targeted 1:1 design, which has implications on the conversion efficiency.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.79.Dj Gratings
78.66.Fd III-V semiconductors
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Density functional theory investigation of N interstitial migration in GaN

R. R. Wixom and A. F. Wright

J. Appl. Phys. 100, 123108 (2006); http://dx.doi.org/10.1063/1.2402589 (3 pages)

Online Publication Date: 27 December 2006

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Using density-functional total energy calculations, we investigated N interstitial migration in GaN. Two migration paths were considered. The first path confines motion to a single c-plane of the lattice, while the second path involves movement both perpendicular and parallel to the c-axis. The latter path has a lower barrier for the positive charge states and will be the dominant mechanism for migration of the N interstitial in p-type GaN. The calculated barriers are 1.79, 2.12, and 1.98 eV for the +1, +2, and +3 charge states. These barriers are consistent with recent experimental results and indicate that interstitials will be mobile at typical processing temperatures.
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61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect
66.30.Lw Diffusion of other defects

Sign reversal and light controlled tuning of circular polarization in semimagnetic CdMnSe quantum dots

T. Schmidt, M. Scheibner, L. Worschech, A. Forchel, T. Slobodskyy, and L. W. Molenkamp

J. Appl. Phys. 100, 123109 (2006); http://dx.doi.org/10.1063/1.2399895 (5 pages) | Cited 10 times

Online Publication Date: 27 December 2006

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Circularly polarized luminescence of CdMnSe quantum dots in magnetic fields up to 5 T is studied for nominal Mn concentrations of 0%, 1%, and 2% by using a photoelastic modulator technique. The exciton g factors as well as spin relaxation times were determined from the polarized luminescence taking into account the exciton lifetimes, which were also extracted by means of time-resolved photoluminescence spectroscopy. For quantum dots without Mn and with 2% Mn exciton g factors of −1.62 and +1.32, respectively, were found. The quantum dots with 1% Mn show a vanishing small value of g for small excitation powers. For this structure the polarization properties are dominated by the optical orientation. Interestingly, for the 1% Mn quantum dots with increasing excitation power considerable changes of the polarization and the exciton g factor were observed which are interpreted in terms of heating effects. From the power dependence indirect heating via phonons and above a critical value direct heating due to photocarriers were identified to result in drastic changes of the circular polarized quantum dot emission.
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78.67.Hc Quantum dots
75.50.Pp Magnetic semiconductors
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Growth of short-period InAs/GaSb superlattices

H. J. Haugan, K. Mahalingam, G. J. Brown, W. C. Mitchel, B. Ullrich, L. Grazulis, S. Elhamri, J. C. Wickett, and D. W. Stokes

J. Appl. Phys. 100, 123110 (2006); http://dx.doi.org/10.1063/1.2401280 (5 pages) | Cited 13 times

Online Publication Date: 27 December 2006

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The purpose of this work is to explore materials for midinfrared detectors that can operate at room temperature. Shorter-period InAs/GaSb superlattices (SLs) have larger intervalance band separations, which are beneficial for reducing Auger recombination and tunneling current, thus making room temperature operation possible. To test these possibilities, several short-period SLs ranging from 50 to 11 Å were grown and their morphological properties were carefully monitored by transmission electron microscopy. The effect of structural degradation caused by the period reduction on the optical properties was studied using low-temperature photoluminescence (PL). The samples with larger periods (50–32 Å) showed excellent structural qualities and produced narrow full width at half maximum (FWHM) of the PL peak (5 meV). As the period approached 24 Å, slight layer thickness undulations within the SLs were observed and these undulations intensified as the period further reduced to 17 Å. These structural degradations strongly influence optical properties causing significant broadening in the FWHM and higher residual carrier concentration in the shorter-period SLs. With slower growth rates, samples with periods as thin as 19 Å were grown without significant layer undulations.
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68.65.Cd Superlattices
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.55.Cr III-V semiconductors
68.37.Lp Transmission electron microscopy (TEM)

Enhanced modal gain of multilayer InAs/InGaAs/GaAs quantum dot lasers emitting at 1300 nm

A. Salhi, L. Fortunato, L. Martiradonna, R. Cingolani, M. De Vittorio, and A. Passaseo

J. Appl. Phys. 100, 123111 (2006); http://dx.doi.org/10.1063/1.2402744 (4 pages) | Cited 9 times

Online Publication Date: 28 December 2006

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The optical properties of multilayer InAs/InGaAs quantum dots (QDs) with different GaAs barrier thicknesses have been investigated. The photoluminescence (PL) intensity is found to increase with increasing GaAs barrier thickness. For thicknesses larger than 40 nm the PL intensity increases linearly with the number of the QD layers, with a considerable narrowing of the full width at half maximum (from 33 to 26 meV for active regions consisting of three QD layers). This growth protocol has been applied to laser structures containing stacked InAs/InGaAs QD layers. The broad area processed devices exhibit a modal gain as high as 30 and 41 cm−1 for structures embedding five and seven QD layers, respectively, which corresponds to 6 cm−1 per QD layer. The internal quantum efficiency and the transparency current density per QD layer were approximately 70% and 10 A/cm2, respectively, for both structures.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
78.67.Hc Quantum dots
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.55.Hx Other solid inorganic materials
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Spectral narrowing of emission in self-assembled colloidal photonic superlattices

Kasper Baert, Kai Song, Renaud A. L. Vallée, Mark Van der Auweraer, and Koen Clays

J. Appl. Phys. 100, 123112 (2006); http://dx.doi.org/10.1063/1.2402029 (7 pages) | Cited 11 times

Online Publication Date: 29 December 2006

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We report on the influence of a well-designed passband in the stop band of a suitably engineered self-assembled colloidal photonic crystal superlattice on the steady-state emission properties of infiltrated fluorophores. The photonic superlattice was built by convective self-assembly of slabs of silica spheres of two different sizes. Transmission experiments on the engineered photonic crystal structure show two stop bands with an effective passband in between. The presence of this passband results in a narrow spectral range of increased density of states for photon modes. This shows up as a decrease in the emission suppression (enhancement of the emission) in the narrow effective passband spectral region. These experiments indicate that the threshold for lasing can possibly be lowered by spectrally narrowing the emission of fluorophores infiltrated in suitably engineered self-assembled photonic crystal superlattices, and are therefore important towards the realization of efficient all-optical integrated circuits from functionalized photonic superlattices and heterostructures.
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42.70.Qs Photonic bandgap materials
78.55.Hx Other solid inorganic materials
82.70.Dd Colloids
42.55.Tv Photonic crystal lasers and coherent effects
42.55.Rz Doped-insulator lasers and other solid state lasers

Characterization of guided resonances in photonic crystal slabs using terahertz time-domain spectroscopy

Zhongping Jian and Daniel M. Mittleman

J. Appl. Phys. 100, 123113 (2006); http://dx.doi.org/10.1063/1.2399335 (5 pages) | Cited 7 times

Online Publication Date: 29 December 2006

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We describe experimental studies of guided resonances in two-dimensional photonic crystal slabs using coherent single-cycle terahertz pulses. Our measurements directly reveal two stages of pulse transmission in the time domain: an initial pulse resulting from the direct transmission through the photonic crystal slab and a long-lived decaying tail resulting from the finite lifetime of guided resonance modes. These reflect the coupling of a set of discrete modes to the free-space continuum, which produces guided resonances with Fano resonance profiles. Phase spectra are also obtained experimentally, and these also exhibit the signatures of guided resonances. By changing the incident angle of the input beam, we change the spectrum of guided resonances excited by the incident wave. Our experimental results are in good agreement with numerical simulations.
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42.70.Qs Photonic bandgap materials
78.70.Gq Microwave and radio-frequency interactions
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
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Anomalous conductivity and secondary electron emission in Hall effect thrusters

L. Garrigues, G. J. M. Hagelaar, C. Boniface, and J. P. Boeuf

J. Appl. Phys. 100, 123301 (2006); http://dx.doi.org/10.1063/1.2401773 (9 pages) | Cited 10 times

Online Publication Date: 19 December 2006

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This paper is devoted to the study of the effects of electron-wall interactions on cross magnetic field electron momentum and energy losses in Hall effect thrusters. By coupling a semianalytical model of the wall sheath similar to models used by several authors in this context, with a two-dimensional hybrid simulation of a Hall effect thruster, we find that the cross magnetic field conductivity enhanced by electron-wall collisions and secondary electron emission is not sufficient to explain the conductivity deduced from experiments. Calculated current-voltage curves including electron-wall collisions from a standard sheath model as the sole “anomalous” conductivity mechanism do not reproduce the measurements, especially at high discharge voltages, and for various wall ceramics. Results also show that a one-dimensional description of electron-wall collisions with a constant radial plasma density profile as used by many authors leads to an overestimation of the contribution of electron-wall interactions to cross magnetic field conductivity.
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52.25.Fi Transport properties
52.25.Tx Emission, absorption, and scattering of particles
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.75.Di Ion and plasma propulsion
52.40.Hf Plasma-material interactions; boundary layer effects
52.40.Kh Plasma sheaths

Two-dimensional simulation of ac-driven microplasmas confined to 100–300 μm diameter cylindrical microcavities in dielectric barrier devices

Jeong Hyun Seo and J. Gary Eden

J. Appl. Phys. 100, 123302 (2006); http://dx.doi.org/10.1063/1.2398024 (8 pages) | Cited 14 times

Online Publication Date: 19 December 2006

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Cylindrical microcavity plasma devices with diameters (D) in the 100–300 μm range and a dielectric barrier structure similar to that described by Park et al. [J. Appl. Phys. 99, 026107 (2006) ] for Al/Al2O3 devices have been investigated numerically. A two-dimensional fluid simulation of microplasmas in Ne/7% Xe gas mixtures with pD values (where p is the total gas pressure) in the 3–9 Torr cm interval yields the temporal history of the spatially resolved electron and ion number densities in response to a 250 kHz bipolar excitation wave form. Calculations show two distinct regions of plasma development, along the microcavity axis and near the wall, each of which dominates the plasma characteristics in separate pD regions. For low pD values (<4 Torr cm), the negative glow produced at the cavity wall extends to the microcavity axis which, in combination with the strong axial electric field, produces an intense glow discharge on axis. For 4≲pD≲6 Torr cm, a weakened axial discharge is observed early in the life of the plasma but the radial variation of the electron density flattens. Further increases in the gas pressure (to the largest pD values investigated, 6–9 Torr cm) result in the retreat of the negative glow to the vicinity of the microcavity wall, thereby producing a diffuse but annular discharge. Even at the higher pD values, the axial discharge appears to facilitate ignition of the negative glow. The predictions of the simulations are consistent with the behavior of Al/Al2O3 microplasma devices for which D = 100–300 μm.
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52.50.Dg Plasma sources
52.65.Kj Magnetohydrodynamic and fluid equation
52.75.-d Plasma devices
52.40.Hf Plasma-material interactions; boundary layer effects
52.80.Hc Glow; corona
52.25.Fi Transport properties

Ion beam generation from sheath field of grid electrode and its application to surface treatment

Yong-Sung Cho, Hae June Lee, Chung-Hoo Park, Ho-Jun Lee, and Sung-Kwan Lee

J. Appl. Phys. 100, 123303 (2006); http://dx.doi.org/10.1063/1.2400390 (5 pages) | Cited 2 times

Online Publication Date: 20 December 2006

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As plasma immersion ion implantation using a conducting grid is very useful to reduce the effect of capacitance and charging in surface modification, it is broadly applied in the fields of insulating material implantation. On the other hand, there have been only few attempts to analyze the sheath dynamics including the conducting grid. If the bias voltage applied to the conducting grid is in the range of hundreds of volts for sputtering, or the energy for local restructuring of the atomic arrangement is much lower than voltage for implantation, the surface charge and space charge substantially affect the incident ion energy and ion current to the surface. The formation of the space and surface charges during one bias pulse period are thus analyzed through a one-dimensional and a two-dimensional particle-in-cell simulation. Experiment with the optimally designed grid on the basis of the simulation results is conducted, and the results of both cases with grid and without grid are compared. The improvement of adhesion is yielded by increasing surface roughness and chemical change in the polyurethane treatment using the conducting grid.
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52.40.Kh Plasma sheaths
52.40.Hf Plasma-material interactions; boundary layer effects
52.65.Rr Particle-in-cell method
52.77.Dq Plasma-based ion implantation and deposition
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.35.Np Adhesion

Micrometer-scale discharge in high-pressure H2O and Xe environments including supercritical fluid

Masayoshi Sawada, Takaaki Tomai, Tsuyohito Ito, Hideyuki Fujiwara, and Kazuo Terashima

J. Appl. Phys. 100, 123304 (2006); http://dx.doi.org/10.1063/1.2400802 (5 pages) | Cited 8 times

Online Publication Date: 22 December 2006

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We generated micrometer-scale discharge in high-pressure H2O and Xe up to supercritical conditions. In our previous paper, we reported the existence of two peculiar features in the breakdown voltages under high-pressure CO2. The first one was the downward shift at the right-hand side of Paschen’s curve above about 2.5 MPa, and the second one was the drastic decrease in the breakdown voltages near the critical point. We have experimentally confirmed that these features are also observed in H2O and Xe, even though there are some differences among these materials. Our theoretical fitting involving a density fluctuation term FD agrees well with the experimental results, especially for Xe. We suppose that these unique features are brought about by decreases in the electron-to-particle cross section σ, ionization potential φi, and secondary electron coefficient γ′ and changes in the discharge space.
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52.80.Dy Low-field and Townsend discharges
52.25.Jm Ionization of plasmas
52.25.Gj Fluctuation and chaos phenomena
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Tx Emission, absorption, and scattering of particles

Molecular dynamics study on Ar ion bombardment effects in amorphous SiO2 deposition processes

Masafumi Taguchi and Satoshi Hamaguchi

J. Appl. Phys. 100, 123305 (2006); http://dx.doi.org/10.1063/1.2401651 (9 pages) | Cited 5 times

Online Publication Date: 22 December 2006

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Argon ion bombardment effects on growing amorphous SiO2 films during reactive sputtering deposition processes were examined based on molecular dynamics (MD) and Monte Carlo (MC) simulation techniques. The system we have considered here is a film that is subject to energetic Ar bombardment while it is formed by surface reactions of Si and O atoms separately supplied at low kinetic energies. It has been found that (1) Ar injections preferentially sputter O atoms from the surface over Si and (2) also have a compressing effect on the growing film during the deposition process. In other words, our MD/MC simulations have demonstrated at the atomic level that, with higher energy Ar injections, an amorphous SiO2 film grown in a reactive sputtering deposition process is denser and more Si rich.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth

Electrical breakdown in the microscale: Testing the standard theory

Emmanouel Hourdakis, Garnett W. Bryant, and Neil M. Zimmerman

J. Appl. Phys. 100, 123306 (2006); http://dx.doi.org/10.1063/1.2400103 (6 pages) | Cited 4 times

Online Publication Date: 28 December 2006

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We present breakdown voltage measurement data in air taken with a technique we have recently developed and present calculations that show that the common assumption that one protrusion is responsible for the observed current is not warranted. The data suggest that below 10 μm of electrode separation the dominant effect is field emission of electrons. Analyzing the data in that regime, using the theory of standard field emission and field amplification on the surface of a conductor, we come to a prediction about the geometry of the surface protrusions on the electrodes. We look for these protrusions using an atomic force microscope. We find several reasons why the standard theory does not appear to explain our data and conclude that the standard theory is not sufficient.
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52.80.-s Electric discharges
52.25.Tx Emission, absorption, and scattering of particles
52.40.Hf Plasma-material interactions; boundary layer effects
52.70.Ds Electric and magnetic measurements
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Metal organic vapor phase epitaxy of BiSbTe3 films on (001) GaAs vicinal substrates

Jeong-Hun Kim, Dae-Yong Jeong, Jin-Sang Kim, and Byeong-Kwon Ju

J. Appl. Phys. 100, 123501 (2006); http://dx.doi.org/10.1063/1.2399305 (4 pages) | Cited 8 times

Online Publication Date: 18 December 2006

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We have investigated the growth of BiSbTe3 films by metal organic vapor phase epitaxy on (001) GaAs vicinal substrates. A detailed experimental study of the surface morphologies of BiSbTe3 films grown on GaAs (001) vicinal surfaces was carried out and is discussed in this paper with a view to understanding the step-step interaction kinetics that result in step bunching. BiSbTe3 layers grown on nominal (001) GaAs substrates exhibit triangular facet structures consisting of atomically flat plateau areas separated by steps. In contrast, the growth of films on vicinal substrates was found to result in regular arrays of terrace step structures. The formation of step bunches and rectangular terraces on such film surface is attributed to the preferential incorporation of adatoms at step or kink sites and lateral growth rate anisotropy.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.35.B- Structure of clean surfaces (and surface reconstruction)

Influence of substitutional metallic impurities on the performances of p-type crystalline silicon solar cells: The case of gold

S. Dubois, O. Palais, M. Pasquinelli, S. Martinuzzi, and C. Jaussaud

J. Appl. Phys. 100, 123502 (2006); http://dx.doi.org/10.1063/1.2400801 (8 pages) | Cited 5 times

Online Publication Date: 18 December 2006

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The influence of a gold bulk contamination on the performances of boron doped p-type crystalline silicon solar cells is investigated for different base doping levels and different kinds of materials, such as float zone Si, Czochralski Si, and multicrystalline Si. Solar cells are made from intentionally contaminated silicon wafers. By monitoring the evolution of the electrically active substitutional gold concentration by means of bulk lifetime and minority carrier diffusion length measurements, this paper highlights the eventual gettering or hydrogenation effects occurring throughout the whole process but also of the danger of such an impurity in materials containing large densities of extended defects generating recombination centers by means of the impurity-defect interaction.
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61.72.Yx Interaction between different crystal defects; gettering effect
84.60.Jt Photoelectric conversion
61.72.uf Ge and Si
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Raman scattering studies of Te doped In0.14Ga0.86As0.13Sb0.87 alloys grown on GaSb by liquid phase epitaxy

J. Díaz-Reyes, E. López-Cruz, J. G. Mendoza-Álvarez, and S. Jiménez-Sandoval

J. Appl. Phys. 100, 123503 (2006); http://dx.doi.org/10.1063/1.2400807 (4 pages) | Cited 2 times

Online Publication Date: 18 December 2006

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Using the liquid phase epitaxy technique under supercooling conditions we have grown In0.14Ga0.86As0.13Sb0.87 layers doped with tellurium lattice-matched to (100) n-GaSb. Layers doped with Te were accomplished by incorporating Sb2Te3 pellets into the growth melt in the range from 6.48×10−6M to 4.31×10−4M. Using Raman spectroscopy we characterized the structural quality. Two main bands are observed in the Raman spectra centered at 230 and 245 cm−1 which depend strongly on the molar concentration of Sb2Te3. The assignation of the observed vibrational modes to GaAs-like and to (GaSb+InAs)-like mixture modes is discussed using the random-element isodisplacement (REI) model. The REI model seems to describe the observed behavior of vibrational modes reasonably.
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81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
63.20.-e Phonons in crystal lattices

Influence of the annealing treatments on the luminescence properties of SiO/SiO2 multilayers

O. Jambois, H. Rinnert, X. Devaux, and M. Vergnat

J. Appl. Phys. 100, 123504 (2006); http://dx.doi.org/10.1063/1.2402976 (6 pages) | Cited 21 times

Online Publication Date: 19 December 2006

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The formation of silicon nanocrystals (Si-ncs) and their room temperature photoluminescence (PL) properties were investigated in samples elaborated by the evaporation method. Silicon oxide (SiO) single layer and SiO/SiO2 multilayers with different SiO layer thicknesses from 1 to 5 nm were prepared and annealed at different temperatures up to 1050 °C. The structure and the formation of Si-nc were studied by transmission electron microscopy (TEM) and by Fourier transform infrared (FTIR) absorption spectroscopy. It is demonstrated that the Si-ncs appear by the phase separation process from SiO due to the annealing treatments. Contrary to the SiO single layer, the multilayers are a powerful system to obtain highly luminescent Si-nc and to control the Si-nc size for SiO layer thicknesses lower than or equal to 4 nm. It is clearly shown that, in agreement with the quantum confinement theory, the PL energy is a decreasing function of the Si-nc size. However, thanks to the correlation between FTIR, TEM, and PL results, it is demonstrated that the PL energy is also strongly dependent on the quality of the matrix in which the Si-nc are embedded. A model based on the existence of a SiOx shell surrounding the Si-nc is proposed to explain the PL results.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Ap Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
61.72.Cc Kinetics of defect formation and annealing

Solid-liquid interfacial energy of pyrene

S. Akbulut, Y. Ocak, U. Böyük, M. Erol, K. Keşlioğlu, and N. Maraşlı

J. Appl. Phys. 100, 123505 (2006); http://dx.doi.org/10.1063/1.2402098 (7 pages) | Cited 12 times

Online Publication Date: 20 December 2006

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The equilibrated grain boundary groove shapes for commercial purity pyrene (PY) were directly observed by using a temperature gradient stage. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient and solid-liquid interfacial energy of PY have been determined to be (8.9±0.9)×10−8 K m and (21.9±3.3)×10−3 J m−2 with the present numerical model and Gibbs-Thomson equation, respectively. The grain boundary energy of PY phase has been determined to be (42.8±7.3)×10−3 J m−2 from the observed grain boundary groove shapes. Thermal conductivity ratio of liquid phase to solid phase has also been measured to be 0.89.
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68.35.Md Surface thermodynamics, surface energies
61.72.Mm Grain and twin boundaries
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
64.70.D- Solid-liquid transitions

First-order perturbation solutions of embedded strained wires

C.-H. Chiu and Hangyao Wang

J. Appl. Phys. 100, 123506 (2006); http://dx.doi.org/10.1063/1.2400392 (10 pages) | Cited 1 time

Online Publication Date: 20 December 2006

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The paper presents the first-order perturbation solutions to the two-dimensional elasticity problems of strained wires embedded in a multilayered film-substrate system with homogeneous elastic properties. The solutions are accurate to the first order of the characteristic slope of the wires; the expressions of the solutions are concise for wires containing multiple facets; and the solutions are valid for single wire, multiple wires with different shapes, and a periodic array of identical wires. The perturbation solutions provide an efficient scheme for studying the effects of embedded wires on the stresses in the multilayered system.
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46.25.-y Static elasticity
68.65.Ac Multilayers
68.60.Bs Mechanical and acoustical properties
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