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15 Nov 2004

Volume 85, Issue 20, pp. 4561-4807

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 4768 (2004); http://dx.doi.org/10.1063/1.1818331 (3 pages)

G. Walter, N. Holonyak, M. Feng, and R. Chan
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Photorefractive polymer composite operating at the optical communication wavelength of 1550 nm

Savaş Tay, Jayan Thomas, Muhsin Eralp, Guoqiang Li, Bernard Kippelen, Seth R. Marder, Gerald Meredith, Axel Schülzgen, and N. Peyghambarian

Appl. Phys. Lett. 85, 4561 (2004); http://dx.doi.org/10.1063/1.1826224 (3 pages) | Cited 12 times

Online Publication Date: 16 November 2004

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A photorefractive polymer composite sensitized at 1550 nm through direct two-photon absorption has been developed. We show an external diffraction efficiency of 3% in four-wave-mixing experiments and perform holographic reconstruction of distorted images utilizing thin-film devices made of this polymer composite. Amongst other potential applications, the demonstration of accurate, dynamic aberration correction through holography in this all-organic photorefractive device presents an alternative to complex adaptive optics systems currently employed in through-air optical communication links.
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42.70.Jk Polymers and organics
42.40.Eq Holographic optical elements; holographic gratings
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Gi Light-sensitive materials
42.15.Fr Aberrations

Wave fields measured inside a negative refractive index metamaterial

Steven A. Cummer and Bogdan-Ioan Popa

Appl. Phys. Lett. 85, 4564 (2004); http://dx.doi.org/10.1063/1.1823595 (3 pages) | Cited 19 times

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Measured spatial variations of field phase and amplitude versus position inside a wire/split ring resonator negative refractive index metamaterial are presented that show that the phase velocity inside a negative index material points toward the source and consequently that phase velocity and energy flow are reversed in such a medium. These measurements directly demonstrate the fundamental behavior of electromagnetic waves in a negative refractive index material. The same internal field measurements are also used to accurately and reliably measure the effective bulk properties of the negative index metamaterial.

Time- and spectrally resolved ultrafast gain dynamics of a semiconductor optical amplifier under phase-correlated multiwavelength pulse amplification

Luis C. Archundia, Bojan Resan, and Peter J. Delfyett

Appl. Phys. Lett. 85, 4567 (2004); http://dx.doi.org/10.1063/1.1823037 (3 pages) | Cited 1 time

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The ultrafast gain dynamics of an AlGaAs semiconductor optical amplifier (SOA) are measured under phase-correlated multiwavelength pulse amplification using time-resolved pump–probe techniques. Both the temporal and spectral gain dynamics are measured. Carrier heating due to two photon absorption, carrier cooling, four-wave mixing, and cross-phase modulation effects are observed. These effects are evident when amplifying dispersion compensated pulses, and it is shown how these effects decrease when amplifying nondispersion compensated (chirped) pulses. This helps to avoid nonlinear effects in the gain media (SOA), which, in turn, helps to support the operation of external cavity multiwavelength semiconductor mode-locked lasers where the intracavity pulses are inherently chirped.

Ultrafast electron capture into p-modulation-doped quantum dots

K. Gündoğdu, K. C. Hall, Thomas F. Boggess, D. G. Deppe, and O. B. Shchekin

Appl. Phys. Lett. 85, 4570 (2004); http://dx.doi.org/10.1063/1.1815371 (3 pages) | Cited 43 times

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Electron and hole relaxation kinetics are studied in modulation-doped InAs quantum dots using femtosecond time-resolved photoluminescence experiments. We demonstrate that, as a result of doping, carrier relaxation from the barrier layers to the quantum dot ground states is strongly enhanced due to rapid electron–hole scattering involving the built-in carrier population. Results for p-doped quantum dots reveal a threefold decrease in the room-temperature electron relaxation time relative to corresponding undoped quantum dots. Our findings are promising for the development of high-speed, GaAs-based quantum dot lasers with modulation speeds in excess of 30 GHz.

Room-temperature, mid-infrared (λ=4.7 μm) electroluminescence from single-stage intersubband GaAs-based edge emitters

D. P. Xu, A. Mirabedini, M. D’Souza, S. Li, D. Botez, A. Lyakh, Y-J. Shen, P. Zory, and C. Gmachl

Appl. Phys. Lett. 85, 4573 (2004); http://dx.doi.org/10.1063/1.1819518 (3 pages) | Cited 4 times

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GaAs-based, single-stage, intersubband devices with active regions composed of deep quantum wells (i.e., In0.3Ga0.7As) and high AlGaAs barriers display strong room-temperature emission at λ=4.7 μm. The structures are grown by metalorganic chemical vapor deposition. The large energy barriers (∼360 meV) for electrons in the upper energy level of the active region strongly suppress both the carrier leakage as well as the tunneling escape rate out of the wells. As a result, the ratio of emissions at 80 and 300 K is as low as 2.0, and thus there is considerably less need for a Bragg mirror/transmitter-type region. Devices with virtually 100% tunneling injection efficiency have been realized, and their room-temperature spectra are narrow: 25 meV full width at half maximum. These deep-well, single-stage structures are intended for use as the emitting units in two-dimensional, intersubband quantum-box lasers, or as the stages of quantum-cascade lasers for efficient, room-temperature operation in the 3–5-μm wavelength range.

Efficient white light emission in conjugated polymer homojunctions

Guey-Kai Ho, Hsin-Fei Meng, Shi-Chang Lin, Sheng-Fu Horng, Chain-Shu Hsu, Lai-Cheng Chen, and Shu-Mei Chang

Appl. Phys. Lett. 85, 4576 (2004); http://dx.doi.org/10.1063/1.1813643 (3 pages) | Cited 41 times

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We study polymer light-emitting diodes with a homojunction, i.e., junction between two layers with the same host material. One layer is poly (9,9-dioctylfluorene-2,7-diyl) (PFO) host blended with a small amount of poly (2-methoxy-5 (2'-ethyl-hexyloxy)-1,4-phenylene vinylene), another layer is either pure PFO or PFO host blended with green-emitting polyfluorene copolymers. Such homojunction devices are solution processed and show efficient white light emission. The peak luminance 3000 cd∕m2 is reached at 10 V with Internationale de L’Eclairage (CIE) coordinate (0.34, 0.34).
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence

Study of ultrahigh-order modes in a symmetrical metal-cladding optical waveguide

Haifeng Lu, Zhuangqi Cao, Honggen Li, and Qishen Shen

Appl. Phys. Lett. 85, 4579 (2004); http://dx.doi.org/10.1063/1.1823594 (3 pages) | Cited 24 times

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We report theory and experiment on ultrahigh-order modes in a symmetrical metal-cladding thick optical waveguide. The waveguide consists of a LiNbO3 slab or a glass slab with a thickness greater than 0.1 mm, two gold films deposited on the upper and bottom sides of the slab serving as the cladding of the waveguide. By using the free-space coupling technique, ultrahigh-order modes (m>2000) are excited, and its high sensitivity to both refractive index and thickness of the guide, as well as the polarization independence are demonstrated.
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42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.65.Bn Piezoelectric and electrostrictive constants

Pulsed laser induced spontaneous gratings on a surface of azobenzene polymer

Naoto Tsutsumi and Arata Fujihara

Appl. Phys. Lett. 85, 4582 (2004); http://dx.doi.org/10.1063/1.1823013 (3 pages) | Cited 3 times

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Self-organized spontaneous gratings were induced on a surface of azobenzene polymer by an irradiation of frequency doubled neodymium doped yttrium–aluminum–garnet pulsed laser. Irradiation of uniform single laser beam at normal incidence induced periodic line shaped structures on a polymer surface. The structure is so-called laser induced periodic surface structure (LIPSS) which was formed along the direction parallel to the polarization direction of pulsed laser. The LIPSS was formed above the critical thickness around 60 nm. Irradiation of s-polarized holographic interference beams induced the distinguished holographic surface relief grating (SRG) structures. Irradiation of p-polarized holographic interference beams induced egg crate-like (ECL) structures. A combination of holographic SRG and sequential LIPSS is the likely cause of the ECL patterns observed in this work.

Wavelength shifting in photonic bandgap microcavities with isotropic media

Andrea Di Falco, Claudio Conti, and Gaetano Assanto

Appl. Phys. Lett. 85, 4585 (2004); http://dx.doi.org/10.1063/1.1823036 (3 pages) | Cited 3 times

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By coupled mode theory in the time domain and a finite-difference time-domain code, we investigate wavelength shifting and frequency conversion via four-wave mixing inside a photonic crystal wire in an isotropic Kerr material. The three-dimensional time-resolved analysis yields ultrafast and all-optically tunable frequency conversion of a signal/channel about the pump frequency.

Laser action in Eu-doped GaN thin-film cavity at room temperature

J. H. Park and A. J. Steckl

Appl. Phys. Lett. 85, 4588 (2004); http://dx.doi.org/10.1063/1.1821630 (3 pages) | Cited 43 times

Online Publication Date: 16 November 2004

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Rare-earth-based lasing action in GaN is demonstrated. Room-temperature stimulated emission (SE) was obtained at 620 nm from an optical cavity formed by growing in situ Eu-doped GaN thin films on sapphire substrates. The SE threshold for optical pumping of a ∼1 at.  % Eu-doped GaN sample was ∼10 kW∕cm2. The SE threshold was accompanied by reductions in the emission linewidth and lifetime. A modal gain of ∼43 cm−1 and a modal loss of ∼20 cm−1 were obtained.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Transmission and reflection characteristics of in-plane hetero-photonic crystals

Bong-Shik Song, Takashi Asano, Yoshihiro Akahane, Yoshinori Tanaka, and Susumu Noda

Appl. Phys. Lett. 85, 4591 (2004); http://dx.doi.org/10.1063/1.1823035 (3 pages) | Cited 22 times

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We report transmission and reflection characteristics of in-plane hetero-photonic crystals (IP-HPCs) consisting of two serially connected photonic crystal waveguides with differing lattice constants. We show experimentally and theoretically that the transmission spectrum of the structure corresponds to the transmission frequency range common to both waveguides. Also, there exists a frequency gap where the structure has a guiding mode for one waveguide but not for the neighboring one. Our calculated results reveal that light within the common frequency range is transmitted with approximately 100% efficiency through the waveguides while light within the gap is almost perfectly reflected.

Optimization of ridge height for the fabrication of high performance InGaAsN ridge waveguide lasers with pulsed anodic oxidation

C. Y. Liu, Y. Qu, Shu Yuan, and S. F. Yoon

Appl. Phys. Lett. 85, 4594 (2004); http://dx.doi.org/10.1063/1.1824180 (3 pages) | Cited 7 times

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The dependence of the ridge height on the performance of the ridge waveguide (RWG) lasers has been systematically studied. It was found that the optimum ridge height corresponds to an etching depth where all the p-doped layers above the active region were removed. InGaAsN triple-quantum-well RWG lasers with optimized ridge height were fabricated with pulsed anodic oxidation. The lowest threshold current density (Jth) of 711 A∕cm2 was obtained from a 10×1300 μm2 InGaAsN RWG laser. The corresponding transparency current density (Jtr) of the fabricated InGaAsN RWG lasers was 438 A∕cm2 (equivalent to 146 A∕cm2 per well).

Polarity reversal of the magnetic field induced component of terahertz radiation from InAs surfaces at high density excitation

M. Nakajima, Y. Oda, T. Suemoto, and S. Saito

Appl. Phys. Lett. 85, 4597 (2004); http://dx.doi.org/10.1063/1.1814815 (3 pages) | Cited 3 times

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The excitation density dependence of radiation power and wave forms of the terahertz wave from InAs surface under magnetic fields was investigated. A drastic change of the wave forms was observed at high density excitation and was explained by the polarity reversal of the terahertz wave form induced by the magnetic field. The reversal originates from the crossover of the radiation mechanism of the magnetic induced component from the electrons in the accumulation layer to the diffusion current by the photogenerated electrons at high-density excitation under a magnetic field.

Supercontinuum generation in a fiber grating

P. S. Westbrook, J. W. Nicholson, K. S. Feder, Y. Li, and T. Brown

Appl. Phys. Lett. 85, 4600 (2004); http://dx.doi.org/10.1063/1.1818740 (3 pages) | Cited 13 times

Online Publication Date: 16 November 2004

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We show that supercontinuum generation in a fiber containing a Bragg grating exhibits >10× enhancement near the Bragg resonance wavelength. We also show that the grating dispersion exceeds the waveguide dispersion over a bandwidth far in excess of its photonic band gap. The observed enhancement is consistent with nonlinear Schrödinger equation simulations of the supercontinuum formation that combine grating and waveguide dispersion.
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42.79.Dj Gratings
42.81.Dp Propagation, scattering, and losses; solitons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Optical and electro-optical properties of submicrometer lithium niobate slab waveguides prepared by crystal ion slicing and wafer bonding

Payam Rabiei and Peter Gunter

Appl. Phys. Lett. 85, 4603 (2004); http://dx.doi.org/10.1063/1.1819527 (3 pages) | Cited 31 times

Online Publication Date: 16 November 2004

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LiNbO3 thin film crystals have been produced using crystal ion slicing and wafer bonding. Films with a thickness of 680 nm are produced on a thin layer of SiO2, which is deposited on a substrate with electrodes. The crystalline and optical qualities of the fabricated thin films are investigated and are comparable to bulk LiNbO3 single crystals. The effect of thermal annealing is studied using Rutherford backscattering. The refractive indices and the electro-optical (EO) coefficient of the fabricated films are measured using prism coupling dark line spectroscopy and modified attenuated total reflection. The EO coefficient is equal to r33=31 pm∕V at λ=633 nm.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.79.Gn Optical waveguides and couplers
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk Insulators
78.20.Jq Electro-optical effects
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
81.40.Gh Other heat and thermomechanical treatments
61.72.up Other materials

Ultrafast nonresonant third-order optical nonlinearities in ZnSe for photonic switching at telecom wavelengths

A. Major, F. Yoshino, J. S. Aitchison, P. W. E. Smith, E. Sorokin, and I. T. Sorokina

Appl. Phys. Lett. 85, 4606 (2004); http://dx.doi.org/10.1063/1.1823599 (3 pages) | Cited 2 times

Online Publication Date: 16 November 2004

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We report the steady-state and time-resolved z-scan measurements of the nonresonant third-order optical nonlinearities in ZnSe at telecom wavelengths. The measurements demonstrate that ZnSe could be used for ultrafast all-optical switching at 1310 and 1550 nm.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.An Optical susceptibility, hyperpolarizability
42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.47.-p Spectroscopy of solid state dynamics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

White organic light-emitting diodes based on 2,7-bis(2,2-diphenylvinyl)-9,9′-spirobifluorene: Improvement in operational lifetime

C. H. Chuen, Y. T. Tao, F. I. Wu, and C. F. Shu

Appl. Phys. Lett. 85, 4609 (2004); http://dx.doi.org/10.1063/1.1824178 (3 pages) | Cited 31 times

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Very bright white organic light-emitting diodes were fabricated using 2,7-bis(2,2-diphenylvinyl)-9,9′-spirobifluorene (DPVSBF) doped with [4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran)] (DCJTB) as the emission layer. With a device configuration of ITO∕NPB(40 nm)∕DPVSBF:0.2%DCJTB(11 nm)∕Alq(30 nm)∕LiF(1 nm)∕Al(150 nm), a brightness of 1575 cd∕m2 with an external quantum efficiency of 3.31% and luminous efficiency of 8.00 cd∕A, a power efficiency of 5.35 lm∕W was achieved at a driving current of 20 mA∕cm2 (4.7 V). The brightness reached 66 000 cd∕m2 at 15 V. The Commission Internationale de l’Eclairage coordinates stayed nearly constant, changed from (0.35, 0.36) to (0.32, 0.34) when the voltage increased from 6 to 12 V. The relative operational lifetime of the device increased by a factor of ∼20 compared with a similar device based on 4,4′-bis-(2,2-diphenylvinyl)-1,1′-biphenyl as the source of the blue emission. The much extended half-lifetime was attributed to the higher morphological stability of the DPVSBF.

Terahertz generation by difference-frequency mixing of exciton Wannier–Stark ladder states in biased semiconductor superlattices

B. Rosam, K. Leo, L. Yang, and M. M. Dignam

Appl. Phys. Lett. 85, 4612 (2004); http://dx.doi.org/10.1063/1.1819508 (3 pages) | Cited 8 times

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We report the generation of terahertz (THz) radiation in a biased semiconductor superlattice by difference-frequency mixing of interband transitions. The Wannier–Stark spectrum of the superlattice was selectively excited by two spectrally narrow laser lines. The emitted THz radiation was measured as a function of the energetic splitting and spectral position of the bichromatic excitation. The generation of tunable THz radiation is verified. The results clearly show enhanced THz emission when either continuum or 1s exciton wave packets are excited. Good agreement is obtained between the experiment and the results of an exciton model of the nonlinear coherent dynamics.

Low-voltage, polarization-insensitive, electro-optic modulator based on a polydomain barium titanate thin film

Pingsheng Tang, D. J. Towner, A. L. Meier, and B. W. Wessels

Appl. Phys. Lett. 85, 4615 (2004); http://dx.doi.org/10.1063/1.1819515 (3 pages) | Cited 12 times

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A BaTiO3 thin-film electro-optic waveguide modulator with a half-wave voltage-interaction length product (VπL) of 1.1 V cm at 1.55-μm wavelength is demonstrated. The half-wave voltage and the measured effective electro-optic coefficient are 3.3 V and 162 pm∕V, respectively. The half-wave voltage increases less than 10% over a temperature range of 23–90 °C. Polarization-independent electro-optic modulation was observed and attributed to the polydomain structure of the BaTiO3 film. The unique combination of large electro-optic coefficient and polarization independence illustrates how engineered domain structures in ferroelectric thin films can enable properties and performance unachievable in bulk single crystals.
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Combined electron- and ion-beam imprinter and its applications

Q. Ji, L. Ji, Y. Chen, and K.-N. Leung

Appl. Phys. Lett. 85, 4618 (2004); http://dx.doi.org/10.1063/1.1812367 (3 pages) | Cited 4 times

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A combined electron- and ion-beam system employing a double-chamber plasma source and a single accelerator column has been developed to provide focused electron and positive-ion beams simultaneously, with no need for a separate electron source or accelerating column for sample neutralization. The self-aligned ion and electron beams can be used to micromachine and image a variety of materials, both conducting and insulating. Together with an ion-beam imprinting scheme, the combined electron/ion beam system is compact and provides low-cost, high-throughput, and large-area micromachining.
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52.77.-j Plasma applications
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
61.80.Jh Ion radiation effects
61.82.Ms Insulators
61.80.Fe Electron and positron radiation effects
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Growth of highly (100) oriented lead zirconate titanate films on silicon and glass substrates using lanthanum nitrate as a buffer layer

Jong-Jin Choi, Chee-Sung Park, Gun-Tae Park, and Hyoun-Ee Kim

Appl. Phys. Lett. 85, 4621 (2004); http://dx.doi.org/10.1063/1.1819519 (3 pages) | Cited 7 times

Online Publication Date: 16 November 2004

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Highly oriented lead zirconate titanate [Pb(Zr,Ti)O3; PZT] thin films were deposited on Pt∕Ti∕SiO2∕Si and glass substrates by the sol-gel method using lanthanum nitrate as a buffer layer. When the lanthanum nitrate buffer layer was annealed at temperatures between 450 and 550 °C, the PZT layer coated onto this buffer layer showed strong (100) orientation. The film deposited on the buffer layer had this orientation, regardless of the other deposition conditions, such as the pyrolysis temperature, pyrolysis time, annealing temperature, and heating rate. The lanthanum nitrate buffer layer also acted as a very effective diffusion barrier against Pb–Si interdiffusion, thus allowing for the direct deposition of PZT films on Si, SiO2∕Si, and glass substrates. Using this buffer layer, highly oriented PZT film was fabricated stably and reproducibly, regardless of substrate material and the coating conditions. The nature of the lanthanum nitrate buffer layer and its role in the growth of the highly (100) oriented PZT films were investigated.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
66.30.Ny Chemical interdiffusion; diffusion barriers
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Microscopic study on the behavior of the {311} facet in the selective epitaxial growth of Si(100)

Gun-Do Lee, Seung-Hyun Lim, and Euijoon Yoon

Appl. Phys. Lett. 85, 4624 (2004); http://dx.doi.org/10.1063/1.1818730 (3 pages) | Cited 1 time

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The behavior of the {311} facet, which is observed in the selective epitaxial growth of Si(100), is investigated by ab initio calculations and by tight-binding calculations using the environment-dependent tight-binding Si potential. The most stable structure of the {311} facet in the long range order is found to be 3×2 interstitial structure based on the calculation of the surface energy. By comparing the maximum binding energies of adatoms on various structures of Si(311), it is found that the phase transition observed at ∼700 °C is the transition from the 3×2 interstitial to the 3×1 interstitial structure and the phase transition is responsible for the behavior of the {311} facet. By tight-binding molecular dynamics simulation, it is also confirmed that the transition from the 3×2 interstitial to the 3×1 interstitial structure is induced by an adatom at high temperature and it corresponds to the transition from the 3×2 to the 3×1 phase of the Si(311) surface observed in experiment.

High-resolution transmission electron microscopy analysis of the interface between a Tl-1223 (001) superconducting film and an untextured Ag substrate

Bong-Jun Kim, Yoshio Matsui, Shigeo Horiuchi, Dae-Yeong Jeong, Christian Deinhofer, and Gerhard Gritzner

Appl. Phys. Lett. 85, 4627 (2004); http://dx.doi.org/10.1063/1.1814804 (3 pages) | Cited 6 times

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The interface between a screen-printed (Tl0.5Pb0.5)(Sr0.85Ba0.15)2Ca2Cu3Oy (Tl-1223) superconducting film and an untextured Ag substrate is analyzed by transmission electron microscopy (TEM). Preferential orientation between the Tl-1223 grains and the Ag substrate is found. The (001) plane of Tl-1223 grains is parallel to and the {113} plane of Ag is almost parallel to the interface. High-resolution TEM images show that CuO2 planes contact the faceted {113} planes of Ag substrate at the interface. A mechanism for the preferential growth of the Tl-1223 (001) film on untextured Ag substrate is proposed.

Growth of thick (11math0) GaN using a metal interlayer

P. R. Tavernier, B. Imer, S. P. DenBaars, and D. R. Clarke

Appl. Phys. Lett. 85, 4630 (2004); http://dx.doi.org/10.1063/1.1818736 (3 pages) | Cited 9 times

Online Publication Date: 16 November 2004

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Thick films of (11math0)-oriented GaN have been grown on Ti-coated metal organic chemical vapor deposition templates using hydride vapor phase epitaxy. Significant reductions in crack density were observed enabling 240 μm thick films to be grown on sapphire. The use of Ti interlayers was shown to generate significant fractions of voids at the interlayer regrowth interface facilitating void-assisted separation on cooling. Ti metal layers annealed under optimal conditions were found to produce a TiN nanomask suitable for lateral overgrowth during HVPE. An estimate of the void size required to allow spontaneous delamination of the substrate at the TiN–GaN interface is discussed with reference to growth conditions.
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81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.40.Gh Other heat and thermomechanical treatments

Electrical and optical properties of rod-like defects in silicon

J. P. Goss, P. R. Briddon, T. A. G. Eberlein, R. Jones, N. Pinho, A. T. Blumenau, and S. Öberg

Appl. Phys. Lett. 85, 4633 (2004); http://dx.doi.org/10.1063/1.1814425 (3 pages) | Cited 7 times

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Self-interstitials in silicon can aggregate to form rod-like defects (RLDs) having both electrical and optical activity. We carry out local density functional calculations for both {113} and {111} RLDs to determine their structures and electrical activity. We find that small {113} RLDs are more stable than {111} RLDs but this reverses for larger defects. We attribute the electrical activity of {113} RLDs found in deep level transient spectroscopy studies with the bounding dislocations and the 0.903 eV photoluminescence to vacancy point defects lying on the habit plane.
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