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18 Mar 2002

Volume 80, Issue 11, pp. 1859-2034

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Pulse broadening in a Ne–CuBr–Zn laser system by optical resonance pumping

K. Fujii, K. Uno, F. Tawada, T. Hishida, M. Nishizawa, M. Suzuki, K. Oouchi, R. Tsuji, and H. Saito

Appl. Phys. Lett. 80, 1859 (2002); http://dx.doi.org/10.1063/1.1458074 (3 pages) | Cited 2 times

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A Zn atom is employed as the light source for optical resonance pumping to a high lying energy level of the Cu atom, thereby depopulating both the Cu lower laser level and enhancing the upper laser level via cascading decays that is carried out simultaneously. The width of the lasing pulse broadened by 220% and the peak value increased by 180%. The cascading decay route was clarified by observing the fluorescence lines, λ = 675.1, 793.5, and 809.0 nm, thereby specifying five levels of excitation loop. © 2002 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
32.80.Xx Level crossing and optical pumping
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
42.60.By Design of specific laser systems
32.50.+d Fluorescence, phosphorescence (including quenching)

Broadband tuning and dual-spectral/temporal outputs from a nonresonantly injection-seeded diode laser

D. J. L. Birkin, E. U. Rafailov, and W. Sibbett

Appl. Phys. Lett. 80, 1862 (2002); http://dx.doi.org/10.1063/1.1459488 (2 pages) | Cited 11 times

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We demonstrate spectral narrowing and continuous broadband tuning of the picosecond pulse outputs from a nonresonantly injection-seeded, gain-switched diode laser that can be operated in dual spectral/temporal regimes. A single spectral output was continuously tunable over a range of 85 nm and in a dual-wavelength operation the outputs had spectral separations were adjustable from 3.5 to 53 nm. © 2002 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Room-temperature emission of GaAs/AlGaAs superlattice quantum-cascade lasers at 12.6 μm

S. Anders, W. Schrenk, E. Gornik, and G. Strasser

Appl. Phys. Lett. 80, 1864 (2002); http://dx.doi.org/10.1063/1.1461055 (3 pages) | Cited 23 times

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We report on the lasing properties of quantum-cascade lasers that combine the advantage of strong electron confinement with the superior performance of superlattice structures. To achieve an optimum band offset between wells and barriers, we chose an Al content of the AlGaAs barriers of 45%. We fabricated both conventional Fabry–Pérot lasers, as well as single-mode-emitting distributed-feedback lasers. In pulsed mode, the lasers work well up to temperatures as high as 40 °C. The emission wavelength at this temperature is 12.6 μm. At 78 K, some lasers show a low threshold current density of 1.6 kA/cm2, while others show a high optical peak power of 240 mW. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
78.67.De Quantum wells
73.21.Cd Superlattices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

High-intensity interminiband terahertz emission from chirped superlattices

Rüdeger Köhler, Alessandro Tredicucci, Fabio Beltram, Harvey E. Beere, Edmund H. Linfield, A. Giles Davies, and David A. Ritchie

Appl. Phys. Lett. 80, 1867 (2002); http://dx.doi.org/10.1063/1.1461054 (3 pages) | Cited 15 times

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Electroluminescence at λ ∼ 69 μm (4.3 THz) is reported from interminiband transitions in quantum-cascade structures with superlattice active regions. Spontaneous emission gives a low-temperature linewidth of 2 meV (0.48 THz) with linear light–current characteristics observed up to high-current densities (625 A/cm2), resulting in record output powers of 500 pW. Devices operate up to above liquid-nitrogen temperature, with both emission wavelength and current–voltage characteristics in good agreement with theoretical predictions. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.Cd Superlattices
78.60.Fi Electroluminescence
42.55.Px Semiconductor lasers; laser diodes

Microsecond carrier lifetimes in InGaAsP quantum wells emitting at λ=1.5 μm

J. M. Smith, G. S. Buller, D. Marshall, A. Miller, and C. C. Button

Appl. Phys. Lett. 80, 1870 (2002); http://dx.doi.org/10.1063/1.1459490 (3 pages)

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Time-resolved photoluminescence measurements of an undoped InGaAsP multiple-quantum-well heterostructure at excess carrier densities between 1014 and 1016 cm−3 reveal unexpectedly long carrier lifetimes, in excess of 2 μs. By fitting the appropriate rate equation parameters to our results, we establish that radiative recombination is the dominant relaxation process, and show that nonradiative recombination is much less pronounced than in similar quantum-well structures measured previously. © 2002 American Institute of Physics.
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73.63.Hs Quantum wells
78.47.-p Spectroscopy of solid state dynamics
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Cr III-V semiconductors
78.67.De Quantum wells
73.61.Ey III-V semiconductors

1-GHz-repetition-rate femtosecond optical parametric oscillator

X. P. Zhang, J. Hebling, A. Bartels, D. Nau, J. Kuhl, W. W. Rühle, and H. Giessen

Appl. Phys. Lett. 80, 1873 (2002); http://dx.doi.org/10.1063/1.1461870 (3 pages) | Cited 6 times

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We report a 1-GHz-repetition-rate, low-pump-threshold, all-solid-state femtosecond optical parametric oscillator (OPO) based on periodically poled LiNbO3 and pumped by a GHz repetition rate Ti:sapphire laser. The OPO provides nearly transform-limited 65-fs-signal pulses tunable from 1160 to 1320 nm. The pump threshold is about 580 mW, and 43 mW signal power is obtained with 950-mW-pump power. Higher-order quasi-phase-matched sum frequency generation and second harmonic generation processes produce 10 mW blue light at 486 nm and 15 mW red light at 620 nm. © 2002 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters

Wavelength modulation spectroscopy of single quantum dots

T. H. Stievater, Xiaoqin Li, J. R. Guest, D. G. Steel, D. Gammon, D. S. Katzer, and D. Park

Appl. Phys. Lett. 80, 1876 (2002); http://dx.doi.org/10.1063/1.1461071 (3 pages) | Cited 7 times

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We demonstrate that external cavity diode lasers with large mode-hop-free tuning ranges (up to 80 GHz) together with wavelength modulation spectroscopy can be used to study excitonic transitions in semiconductor nanostructures. Such transitions are characterized by homogeneous linewidths typically on the order of a few GHz. Wavelength modulation spectroscopy offers a high signal-to-noise method for the determination of resonance line shapes. We have used this technique to accurately measure dipole moments and dephasing rates of single semiconductor quantum dot eigenstates. These measurements are important for the use of quantum dots in semiconductor cavities and quantum logic gates, and for an improved understanding of the physics of exciton confinement. © 2002 American Institute of Physics.
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73.21.La Quantum dots
78.67.Hc Quantum dots
42.55.Px Semiconductor lasers; laser diodes
71.35.-y Excitons and related phenomena
42.62.Fi Laser spectroscopy

Inverse opal with an ultraviolet photonic gap

Peigen Ni, Bingying Cheng, and Daozhong Zhang

Appl. Phys. Lett. 80, 1879 (2002); http://dx.doi.org/10.1063/1.1457530 (3 pages) | Cited 12 times

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Photonic crystals composed of TiO2 and air voids fabricated by the template method exhibit an ultraviolet photonic stop band (∼380 nm) in the Γ–L direction. Scanning electron microscopy images show that the inverse opal possesses face-centered-cubic symmetry with a lattice constant of 240 nm. The transmission spectra show that the change in transmittance is one order of magnitude in the gap, which is in accord with the reflection spectrum. © 2002 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Qs Photonic bandgap materials
61.72.Qq Microscopic defects (voids, inclusions, etc.)
42.50.-p Quantum optics
78.40.Ha Other nonmetallic inorganics
61.66.Fn Inorganic compounds

Real index-guided InGaAlP red lasers with buried tunnel junctions

T. C. Lu, H. M. Shieh, and S. C. Wang

Appl. Phys. Lett. 80, 1882 (2002); http://dx.doi.org/10.1063/1.1459763 (3 pages) | Cited 2 times

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Real index-guided buried ridge InGaAlP 650 nm band lasers with p+–n+ buried tunnel junctions are demonstrated. Located on top of the buried ridges, the tunnel junctions, made of InGaAs/GaAs superlattices with modulation doping, were introduced as the current injection window areas. The large band gap In0.5Al0.5P layers were directly regrown around the ridges using metalorganic chemical vapor deposition to serve as the current blocking layers. Real index optical waveguiding in the lateral direction was also provided by the smaller refractive index of In0.5Al0.5P layers. The lasers showed lower threshold current and higher slope efficiency compared to conventional complex index-guided InGaAlP lasers with GaAs current blocking layers, and had low internal loss of about 5.4 cm−1. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Shift of the photonic band gap in two photonic crystal/liquid crystal composites

Guido Mertens, Thorsten Röder, Ralf Schweins, Klaus Huber, and Heinz-S. Kitzerow

Appl. Phys. Lett. 80, 1885 (2002); http://dx.doi.org/10.1063/1.1461885 (3 pages) | Cited 32 times

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We have investigated the photonic band gap of normal and inverted colloidal crystals which were infiltrated with a nematic liquid crystal. In both systems, the wavelength of the photonic band gap can be tuned by adjusting the temperature. In agreement with recent theoretical predictions, the spectral shift is larger (≈14 nm) in the inverted structure. © 2002 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.70.Df Liquid crystals
78.20.-e Optical properties of bulk materials and thin films
61.30.-v Liquid crystals

Lateral color integration on rare-earth-doped GaN electroluminescent thin films

D. S. Lee and A. J. Steckl

Appl. Phys. Lett. 80, 1888 (2002); http://dx.doi.org/10.1063/1.1461884 (3 pages) | Cited 16 times

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Lateral color integration has been obtained using GaN thin films doped with Er and Eu. These rare-earth doped GaN (GaN:RE) films were grown on Si (111) substrates by molecular beam epitaxy. Independent red and green emissions have been obtained from side-by-side Er and Eu electroluminescent devices. Photoluminescence and electroluminescence operation show green emissions at 537 and 558 nm from Er-doped GaN and red emission at 621 nm from Eu-doped GaN. Two patterning fabrication techniques have been investigated to obtain lateral integration: (a) use of shadow masks during 400 °C growth of GaN:RE films; (b) photoresist liftoff in conjunction with <100 °C GaN:RE growth. Devices fabricated by the shadow mask method were bright enough to be detected under the ambient light at a bias of 30 V. The GaN:RE films were clear and their surfaces were smooth with nanoscale GaN grains. The root mean square surface roughness was measured to be 5–10 nm. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
78.55.Cr III-V semiconductors
78.40.Fy Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.Cf Surface cleaning, etching, patterning

Efficient polymer light-emitting diodes using conjugated polymer blends

Gufeng He, Jie Liu, Yongfang Li, and Yang Yang

Appl. Phys. Lett. 80, 1891 (2002); http://dx.doi.org/10.1063/1.1459770 (3 pages) | Cited 19 times

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Photoluminescence studies have been performed on poly [2,5-bis(cheolestranoxy)-1,4-phenylene vinylene] (BCHA) blends with poly(9,9-dioctylfluorene) (PF). The composition-independent, distinctive emission of BCHA in the BCHA/PF blends suggests the nonexistence of interchain species in the blends, due to polymer chain separation by bulky side groups. The electroluminescence (EL) efficiencies of devices made with BCHA/PF blends were also found to be superior to the BCHA-only devices. For example, the EL efficiency of the BCHA (10%)/PF device was 3.0 cd/A, which is about five times higher than a BCHA device. The basis for this enhancement has been attributed to improved charge injection and charge trapping in BCHA/PF blends. Holes are injected in these blends through the PF component and then transferred and trapped in BCHA, where radiative recombination subsequently occurs. As a result of improved minority-carrier injection, the turn-on voltages of the BCHA/PF devices are also much lower than the BCHA devices. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
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Modification of optical properties by strain-induced piezoelectric effects in ultrahigh-quality V-groove AlGaAs/GaAs single quantum wire

Xing-Quan Liu, Xue-Lun Wang, Mutsuo Ogura, Thierry Guillet, Valia Voliotis, and Roger Grousson

Appl. Phys. Lett. 80, 1894 (2002); http://dx.doi.org/10.1063/1.1459761 (3 pages) | Cited 6 times

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We report tiny strain-induced piezoelectric effects in an ultrahigh-quality AlGaAs/GaAs V-groove quantum wire structure. Zero photoluminescence excitation (PLE) absorption intensities are observed at low temperatures. Excitation power density-dependent optical properties provide evidence that the zero PLE absorption intensities are due to an internal electric field created by tiny strain-induced piezoelectric polarization along the wires, which causes complete spatial separation of the electron and hole wave functions along the wires. Absorption is enhanced by shining a He–Ne laser as a background in order to screen the electric field, which confirms the existence of piezoelectric field effects. © 2002 American Institute of Physics.
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78.67.Lt Quantum wires
78.55.Cr III-V semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
77.65.Ly Strain-induced piezoelectric fields

Thermodynamic stability of high-K dielectric metal oxides ZrO2 and HfO2 in contact with Si and SiO2

Maciej Gutowski, John E. Jaffe, Chun-Li Liu, Matt Stoker, Rama I. Hegde, Raghaw S. Rai, and Philip J. Tobin

Appl. Phys. Lett. 80, 1897 (2002); http://dx.doi.org/10.1063/1.1458692 (3 pages) | Cited 135 times

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We present theoretical and experimental results regarding the thermodynamic stability of the high-k dielectrics ZrO2 and HfO2 in contact with Si and SiO2. The HfO2/Si interface is found to be stable with respect to formation of silicides whereas the ZrO2/Si interface is not. The metal–oxide/SiO2 interface is marginally unstable with respect to formation of silicates. Cross-sectional transmission electron micrographs expose formation of nodules, identified as silicides, across the polycrystalline silicon/ZrO2/Si interfaces but not for the interfaces with HfO2. For both ZrO2 and HfO2, the x-ray photoemission spectra illustrate formation of silicate-like compounds in the MO2/SiO2 interface. © 2002 American Institute of Physics.
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68.37.Lp Transmission electron microscopy (TEM)
79.60.Jv Interfaces; heterostructures; nanostructures
68.35.Fx Diffusion; interface formation
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
82.60.Cx Enthalpies of combustion, reaction, and formation

Growth and characterization of GaInNxAs1−x thin films with band-gap energies in the red-blue portion of the visible spectrum

Jairo A. Cardona-Bedoya, Fernando Gordillo-Delgado, Orlando Zelaya-Angel, Alfredo Cruz-Orea, and Julio G. Mendoza-Álvarez

Appl. Phys. Lett. 80, 1900 (2002); http://dx.doi.org/10.1063/1.1454209 (3 pages) | Cited 3 times

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Using the radio-frequency (rf) sputtering deposition technique, we have grown GaInNxAs1−x thin films on glass substrates at room temperature. The concentration of nitrogen in the films was found to depend mainly on the rf power used to excite the growth plasma. X-ray diffractograms show that the films have small grain sizes and present a broad diffraction band centered close to the (002) diffraction peak of hexagonal GaN. Electron dispersive spectroscopy measurements report N concentrations of x ∼ 0.8 and In concentrations of about 3% indicating that we have grown GaInNxAs1−x alloys in the GaN-rich side. The absorption spectra measured by the photoacoustic technique show that these semiconductor films have band-gap energies ranging between 1.69 and 2.56 eV, when the rf sputtering power is varied in the range 30–80 W. Thus, we show the feasibility to grow GaInNxAs1−x thin films with high N concentrations in which we can tune the band-gap energy in the red-blue portion of the visible spectrum, by a careful control of the growth parameters. © 2002 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Cd Deposition by sputtering
78.66.Fd III-V semiconductors
71.20.Nr Semiconductor compounds
68.55.Nq Composition and phase identification
78.40.Fy Semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

On the effective thermal diffusivity of fiber-reinforced composites

A. Salazar, J. M. Terrón, A. Sánchez-Lavega, and R. Celorrio

Appl. Phys. Lett. 80, 1903 (2002); http://dx.doi.org/10.1063/1.1461422 (3 pages) | Cited 12 times

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Modulated photothermal techniques provide useful methods based on linear relations between measurable quantities to obtain the thermal diffusivity of homogeneous materials. In this letter the applicability of such linear relations in the case of unidirectional fiber-reinforced composites (UFRC) is analyzed. Based on the solution of the propagation of plane thermal waves in a material with aligned buried cylinders, we found that the linear relation valid for homogeneous materials still holds for UFRC. However, its slope does not give the effective thermal diffusivity as derived from the effective thermal conductivity measured by steady-state experiments. Anyway, as the number of cylinder rows increases the thermal diffusivity measured by modulated methods approaches the steady value asymptotically. The model is validated by photothermal measurements performed on calibrated samples. © 2002 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
07.20.-n Thermal instruments and apparatus

Microstructures and mechanical properties of tungsten wire/particle reinforced Zr57Nb5Al10Cu15.4Ni12.6 metallic glass matrix composites

Haein Choi-Yim, Jan Schroers, and William L. Johnson

Appl. Phys. Lett. 80, 1906 (2002); http://dx.doi.org/10.1063/1.1459766 (3 pages) | Cited 31 times

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Tungsten wire or particle reinforced metallic glass matrix composites are produced by infiltrating liquid Zr57Nb5Al10Cu15.4Ni12.6 (Vit106) into tungsten reinforcements at 1150 and at 1425 K. X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy are carried out to characterize the composite. The matrix of the composite processed at 1150 K is mostly amorphous, with some embedded crystals. During processing, tungsten dissolves in the glass-forming melt and upon quenching precipitates over a relatively narrow zone near the interface between the tungsten and matrix. In the composites processed at 1425 K, tungsten dissolves in the melt and diffuses through the liquid medium, and then reprecipitates upon quenching. The faster kinetics at this high temperature results in a uniform distribution of the crystals throughout the matrix. Mechanical properties of the differently processed composites containing wires and particles are compared and discussed. The composites exhibit a plastic strain failure of up to 16% without sacrificing the high-failure strength, which is comparable to monolithic Vit106. © 2002 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity
81.30.Mh Solid-phase precipitation
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.43.Fs Glasses
64.75.-g Phase equilibria

Nitrogen-related local vibrational modes in ZnO:N

A. Kaschner, U. Haboeck, Martin Strassburg, Matthias Strassburg, G. Kaczmarczyk, A. Hoffmann, C. Thomsen, A. Zeuner, H. R. Alves, D. M. Hofmann, and B. K. Meyer

Appl. Phys. Lett. 80, 1909 (2002); http://dx.doi.org/10.1063/1.1461903 (3 pages) | Cited 141 times

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We study the influence of nitrogen, a potential acceptor in ZnO, on the lattice dynamics of ZnO. A series of samples grown by chemical vapor deposition (CVD) containing different nitrogen concentrations, as determined by secondary ion mass spectroscopy (SIMS), was investigated. The Raman spectra revealed vibrational modes at 275, 510, 582, 643, and 856 cm−1 in addition to the host phonons of ZnO. The intensity of these additional modes correlates linearly with the nitrogen concentration and can be used as a quantitative measure of nitrogen in ZnO. These modes are interpreted as local vibrational modes. Furthermore, SIMS showed a correlation between the concentration of incorporated nitrogen and unintentional hydrogen, similar to the incorporation of the p-dopant magnesium and hydrogen in GaN during metalorganic CVD. © 2002 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
63.20.Pw Localized modes
61.72.S- Impurities in crystals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Band gap changes of GaN shocked to 13 GPa

M. D. McCluskey, Y. M. Gupta, C. G. Van de Walle, D. P. Bour, M. Kneissl, and N. M. Johnson

Appl. Phys. Lett. 80, 1912 (2002); http://dx.doi.org/10.1063/1.1455148 (3 pages) | Cited 7 times

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The band gap of GaN under uniaxial-strain compression was determined using time-resolved optical transmission measurements in shock-wave experiments. Shock waves were generated by impacting the GaN samples with c-cut sapphire impactors mounted on projectiles fired by a gas gun. Impact velocities were varied to provide longitudinal stresses ranging from 4.5 to 13 GPa. An abrupt increase of the band gap is observed upon shock-wave compression, followed by a slower increase. By measuring the absorption threshold before and during shock compression of the GaN layer, the band-gap shift for a particular longitudinal stress was obtained. A linear fit to the data yields a band-gap shift of 0.02 eV/GPa. Comparison with ab initio calculations show that this slope lies between the calculated bounds for isotropic and uniaxial compression. Potential reasons for the differences are indicated. © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
62.50.-p High-pressure effects in solids and liquids
78.47.-p Spectroscopy of solid state dynamics

Direct crystallization of the peritectic Nd2Fe14B1 phase by undercooling of bulk alloy melts

Thomas Volkmann, Jianrong Gao, and Dieter M. Herlach

Appl. Phys. Lett. 80, 1915 (2002); http://dx.doi.org/10.1063/1.1461430 (3 pages) | Cited 19 times

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Electromagnetic levitation was used to melt and solidify containerlessly Nd–Fe–B alloys. A method was developed to reduce and evaporate stable solid Nd oxides at the surface of the liquid samples. The oxides otherwise limit the undercoolability of the highly reactive Nd-based alloys. In such a way, undercoolings up to 150 K of the levitation processed samples were achieved. Owing to the large undercooling range, the intermetallic Nd2Fe14B1 phase with the hard magnetic properties was primarily crystallized at undercoolings exceeding 50 K. Solidification of the pro-peritectic γ-Fe with soft magnetic properties was successfully suppressed. At the largest undercoolings, a metastable phase, likely to be of the composition Nd2Fe17Bx (x ≈ 1) is primarily formed while the crystallization of Nd2Fe14B1 phase is followed up in a subsequent step. © 2002 American Institute of Physics.
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64.70.D- Solid-liquid transitions
64.75.-g Phase equilibria
75.50.Ww Permanent magnets

Phase stabilities of “morphotropic” phases in Pb(Zn1/3Nb2/3)O3–PbTiO3 single crystals

Yu Lu, D.-Y. Jeong, Z.-Y. Cheng, T. Shrout, and Q. M. Zhang

Appl. Phys. Lett. 80, 1918 (2002); http://dx.doi.org/10.1063/1.1461902 (3 pages) | Cited 41 times

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Based on the optic and dielectric data acquired under different mechanical and electric conditions and temperature, we show that an orthorhombic phase exists near the morphotropic phase boundary (MPB) (on both the rhombohedral and tetragonal sides of MPB). Because of the proximity of the free energy of this phase to the two other morphotropic phases, i.e., the rhombohedral and tetragonal phases, the experimentally observed phases and phase diagrams near MPB depend crucially on the mechanical and electric conditions as well as the sample history. © 2002 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
81.30.Dz Phase diagrams of other materials

Growth of single-crystal SiO2 film on Ni(111) surface

Manisha Kundu and Yoshitada Murata

Appl. Phys. Lett. 80, 1921 (2002); http://dx.doi.org/10.1063/1.1461052 (3 pages) | Cited 10 times

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We grew a single-crystal SiO2 film on a Ni(111) surface. Atomic hydrogen during initial growth of an amorphous SiO2 film and an ambient oxygen atmosphere during annealing of this film were essential in forming this single-crystal SiO2 film. The film grew with a (√3×√3) R30° crystallographic orientation, and its structure was the high-temperature phase of quartz, i.e., β quartz. In addition, a polycrystalline silicide phase was formed at the SiO2/Ni(111) interface. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Fx Diffusion; interface formation

Time-resolved and time-integrated photoluminescence in ZnO epilayers grown on Al2O3(0001) by metalorganic vapor phase epitaxy

S. W. Jung, W. I. Park, H. D. Cheong, Gyu-Chul Yi, Hyun M. Jang, S. Hong, and T. Joo

Appl. Phys. Lett. 80, 1924 (2002); http://dx.doi.org/10.1063/1.1461051 (3 pages) | Cited 79 times

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We report on photoluminescence (PL) spectra of ZnO films grown by low pressure metalorganic vapor phase epitaxy. For PL measurements, high quality ZnO thin films were epitaxially grown on Al2O3(0001) substrates. Time-integrated PL spectra of the films at 10 K clearly exhibited free A and B excitons at 3.376 and 3.382 eV and bound exciton peaks at 3.360, 3.364, and 3.367 eV. With increasing temperature, intensities of the bound exciton peaks drastically decreased and a free exciton peak was dominant above 40 K. Furthermore, time-resolved PL measurements at the free exciton peak were carried out at room temperature. The decay profiles were of double-exponential form, and the decay time constants of 180 ps and 1.0 ns were obtained using a least-square fit of the data. © 2002 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
81.05.Dz II-VI semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Nanoencapsulation of ZnS:Ag particulates with indium tin oxide for field emission displays

M. Ollinger, V. Craciun, and R. K. Singh

Appl. Phys. Lett. 80, 1927 (2002); http://dx.doi.org/10.1063/1.1453477 (3 pages) | Cited 11 times

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Cathodoluminescence degradation measurements showed that by applying a nanometer-scale indium tin oxide (ITO) coating on micron-sized ZnS:Ag particles, the degradation lifetime was dramatically improved. X-ray photoelectron spectroscopy (XPS) analysis showed that the Zn 2p3/2 and S 2p peaks of the electron beam irradiated ZnS:Ag were shifted to higher binding energies, which correspond to oxidized elements with respect to those found for the commercial ZnS:Ag particulates. The XPS analysis for the ITO coated ZnS:Ag showed a broadening of the Zn 2p3/2 and S 2p peaks, which were a convolution of several peaks. In this case, the Zn 2p3/2 and S 2p peaks corresponding to ZnS were still present together with another shoulder corresponding to the oxidized elements. This difference in the XPS results shows that the ITO coating reduced the degradation rate by slowing the surface chemical changes on the ZnS:Ag powder. © 2002 American Institute of Physics.
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78.66.Vs Fine-particle systems
78.60.Hk Cathodoluminescence, ionoluminescence
85.45.Fd Field emission displays (FEDs)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Jv Interfaces; heterostructures; nanostructures
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Electrical activation studies of GaN implanted with Si from low to high dose

James A. Fellows, Y. K. Yeo, R. L. Hengehold, and D. K. Johnstone

Appl. Phys. Lett. 80, 1930 (2002); http://dx.doi.org/10.1063/1.1458694 (3 pages) | Cited 28 times

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Electrical activation studies of Si-implanted GaN grown on sapphire have been made as a function of ion dose and anneal temperature. Silicon was implanted at 200 keV with doses ranging from 1×1013 to 5×1015 cm−2 at room temperature. The samples were annealed from 1100 to 1350 °C with a 500-Å-thick AlN cap in a nitrogen environment. Samples implanted with high doses ( ≥ 1×1015 cm−2) have optimum anneal temperatures of around 1350 °C, exhibiting a nearly 100% electrical activation efficiency, whereas low dose ( ⩽ 5×1014 cm−2) samples exhibited lower activation efficiencies, but efficiencies increase with anneal temperature even after annealing at 1350 °C. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
61.72.uj III-V and II-VI semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.Cc Kinetics of defect formation and annealing
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