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24 Sep 2001

Volume 79, Issue 13, pp. 1933-2115

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Transport and trapping of photocharges in liquid crystals placed between photoconductive polymer layers

Junho Mun, Choon Sup Yoon, Hyun-Wuk Kim, Su-An Choi, and Jong-Duk Kim

Appl. Phys. Lett. 79, 1933 (2001); http://dx.doi.org/10.1063/1.1400087 (3 pages) | Cited 11 times

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The transport and trapping of photocharges in liquid crystals placed between photoconductive polymer layers was investigated systematically. The transport of the photocharges is explained in terms of current paths that are formed along the bright sites of an interference pattern. Our study shows clearly that charge trapping occurs predominantly in the photoconductive poly(N-vinylcarbazole) layers and not in the insulating poly(vinyl alcohol) layers, contrary to a previous report. © 2001 American Institute of Physics.
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42.70.Df Liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
78.20.Jq Electro-optical effects
73.50.Pz Photoconduction and photovoltaic effects
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
73.61.Ph Polymers; organic compounds
42.79.Dj Gratings
42.70.Gi Light-sensitive materials
42.70.Jk Polymers and organics

Efficiency of GaN/InGaN light-emitting diodes with interdigitated mesa geometry

X. Guo, Y.-L. Li, and E. F. Schubert

Appl. Phys. Lett. 79, 1936 (2001); http://dx.doi.org/10.1063/1.1405145 (3 pages) | Cited 32 times

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GaN/InGaN light-emitting diodes (LEDs) with different mesa structures are studied. The optical emission power as well as current–voltage characteristics of different mesa patterns are measured. The results show that the optical emission of the device with interdigitated patterns is higher than devices with traditional square-shaped patterns. The leakage current is found to increase as the mesa sidewall perimeter increases. Based on the analysis, it is concluded that a surface leakage current flows across the mesa sidewall and the leakage current is directly proportional to the mesa perimeter. The implications of the results for large-area scalable LED structures are discussed. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors

Nonlinear optical properties of chalcogenide glasses: Observation of multiphoton absorption

K. S. Bindra, H. T. Bookey, A. K. Kar, B. S. Wherrett, X. Liu, and A. Jha

Appl. Phys. Lett. 79, 1939 (2001); http://dx.doi.org/10.1063/1.1402158 (3 pages) | Cited 24 times

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We report observation of four- and five-photon absorption in the chalcogenide glasses at the telecommunication wavelengths. The nonlinear refractive index is sufficiently large that the optical switching criterion is satisfied. © 2001 American Institute of Physics.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Infrared and visible emission from organic electroluminescent devices based on praseodymium complex

Ziruo Hong, Chunjun Liang, Ruigang Li, Faxin Zang, Di Fan, Wenlian Li, L. S. Hung, and S. T. Lee

Appl. Phys. Lett. 79, 1942 (2001); http://dx.doi.org/10.1063/1.1391239 (3 pages) | Cited 37 times

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Praseodymium(dibenzoylmethanato)3(bathophenanthroline) [Pr(DBM)3bath] was employed as an emitting and electron transport layer, and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1, 1′-biphenyl-4,4′-diamine (TPD) as a hole transport layer in organic electroluminescent (EL) devices. Bilayer device TPD/Pr(DBM)3bath and trilayer devices TPD/TPD:Pr(DBM)3bath/Pr(DBM)3bath with a different ratio of TPD to the Pr-complex were fabricated. Emission bands at 608 nm (1D2→3H6), 890 nm (1D2→3F2), 1015 nm (1D2→3F3), 1065 nm (1D2→3F4) and 1550 nm (1D2→1G4) originating from the internal f–f transitions of a Pr3+ ion were observed from EL devices using both bilayer and trilayer structures. Decreasing the ratio of TPD to the Pr-complex, the emission of the 1D2→3H6 transition was promoted and that from the exciplex suppressed, which was explained in terms of energy transfer from the ligand to the central ion. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

Pumping picosecond optical parametric oscillators by a pulsed Nd:YAG laser mode locked using a nonlinear mirror

A. A. Mani, L. Dreesen, Ph. Hollander, C. Humbert, Y. Caudano, P. A. Thiry, and A. Peremans

Appl. Phys. Lett. 79, 1945 (2001); http://dx.doi.org/10.1063/1.1405433 (3 pages) | Cited 27 times

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We report on the performances of the mode locking of a flash-lamp-pumped Nd:YAG laser using a frequency-doubling nonlinear mirror combined with a two-photon absorber. Pulse lengths from 12 to 8 ps are generated. We show that the flat shape of the pulse-train envelope generated by the oscillator is adapted for the synchronous pumping of optical parametric oscillators and we demonstrate the efficient generation of an infrared beam tunable from 3800 to 1100 cm−1 with bandwidth of 2 cm−1 in one single conversion stage in LiNbO3 or AgGaS2. The “all-solid-state” laser system enables surface sum-frequency generation spectroscopy to be performed with high sensitivity and high resolution. © 2001 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Bh Lenses, prisms and mirrors

Characteristics of InGaN laser diodes in the pure blue region

Shin-ichi Nagahama, Tomoya Yanamoto, Masahiko Sano, and Takashi Mukai

Appl. Phys. Lett. 79, 1948 (2001); http://dx.doi.org/10.1063/1.1399011 (3 pages) | Cited 22 times

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InGaN multi-quantum-well-structure laser diodes (LDs), whose emission wavelengths are in the pure blue region, were grown on epitaxially laterally overgrown GaN on a free-standing GaN substrate by the metaorganic chemical-vapor deposition method. The wavelength dependence of the InGaN LD characteristics was investigated. These results indicated that there is a strong relationship between the threshold current density and the emission wavelength of LDs. LDs with an emission wavelength of 460 nm were demonstrated. The threshold current density and voltage of these LDs were 3.3 kA/cm2 and 4.6 V, respectively. The estimated lifetime was approximately 3000 h under 50 °C continuous-wave operation at an output power of 5 mW. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Ultraviolet picosecond optical pulse generation from a mode-locked InGaN laser diode

S. Gee and J. E. Bowers

Appl. Phys. Lett. 79, 1951 (2001); http://dx.doi.org/10.1063/1.1405432 (2 pages) | Cited 11 times

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Ultraviolet optical pulses were generated by actively mode locking an external cavity InGaN laser at a wavelength of 409 nm with a temporal pulse duration of 30 ps. The average power was 2 mW and the time–bandwidth product was 1.2. Dynamic detuning plays a major role in pulse development. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Blue InGaN/GaN multiple-quantum-well optically pumped lasers with emission wavelength in the spectral range of 450–470 nm

G. P. Yablonskii, E. V. Lutsenko, V. N. Pavlovskii, I. P. Marko, A. L. Gurskii, V. Z. Zubialevich, A. V. Mudryi, O. Schön, H. Protzmann, M. Lünenbürger, B. Schineller, M. Heuken, H. Kalisch, and K. Heime

Appl. Phys. Lett. 79, 1953 (2001); http://dx.doi.org/10.1063/1.1400766 (3 pages) | Cited 9 times

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Optically pumped lasing in the wavelength range of 450–470 nm in InGaN/GaN multiple-quantum-well heterostructures grown by metalorganic vapor phase epitaxy was achieved and investigated. The energy and power per pulse of the laser were 80 nJ and 10 W correspondingly for one facet at room temperature. The far-field patterns of the laser emission consisted of three light spots near the angles of +30°, −15°, and −45°. The highest operating temperature was 450 K. The photoluminescence and photoluminescence excitation spectrum structures suggest that the quantum dots inside the quantum wells are involved in the recombination mechanism. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.55.Cr III-V semiconductors
78.67.De Quantum wells
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Room-temperature continuous photopumped laser operation of coupled InP quantum dot and InGaP quantum well InP–InGaP–In(AlGa)P–InAlP heterostructures

G. Walter, N. Holonyak, J. H. Ryou, and R. D. Dupuis

Appl. Phys. Lett. 79, 1956 (2001); http://dx.doi.org/10.1063/1.1405153 (3 pages) | Cited 31 times

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Data are presented demonstrating continuous 300 K photopumped InP quantum dot (QD) laser operation (656–679 nm) realized by modifying and coupling, via tunneling, an auxiliary InGaP quantum well (QW) to the QDs of an InP–In(AlGa)P–InAlP heterostructure grown by metalorganic chemical vapor deposition. The In0.49Ga0.51P QW coupled to the InP QDs by a thin (≲20 Å) In0.5Al0.3Ga0.2P barrier overcomes the limitations of carrier collection, lateral transport, and thermalization in the QDs, thus yielding a different form of QD laser. © 2001 American Institute of Physics.
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42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Px Semiconductor lasers; laser diodes

Determination of optical modes in two-dimensional finite-size photonic crystals by photonic resonance scattering

S. Nojima

Appl. Phys. Lett. 79, 1959 (2001); http://dx.doi.org/10.1063/1.1406985 (3 pages) | Cited 15 times

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The analogy of the resonance scattering of an electron by an atom is used to investigate optical modes in two-dimensional finite-size photonic-crystal resonators. This analysis enables us to determine complex resonance energies from which we can estimate optical modes and photon lifetimes in the resonators. The threshold amplitude gain of the laser exploiting this photonic-crystal resonator is inversely proportional to the photon lifetime. This linear relation is found to remain the same irrespective of the dimensionality of the photonic crystal structure, the number of unit cells, and the size of unit cell, as long as the filling factor of the gain cell is fixed. This implies that the two-dimensional finite-size photonic-crystal resonators work well despite complicated feedback mechanisms and the absence of clear-cut cavity mirrors. © 2001 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics

Room-temperature-grown rare-earth-doped GaN luminescent thin films

D. S. Lee and A. J. Steckl

Appl. Phys. Lett. 79, 1962 (2001); http://dx.doi.org/10.1063/1.1406138 (3 pages) | Cited 11 times

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Visible emission has been observed from rare-earth (RE)-doped GaN electroluminescent devices (ELDs) as-grown near room temperature on Si (50–100 °C): red from GaN:Eu, green from GaN:Er, and blue from GaN:Tm. Green emission at 537/558 nm from GaN:Er ELD had a measured brightness of ∼230 cd/m2 at 46 V bias. X-ray diffraction indicates that the low-temperature-grown GaN:Er structure was oriented with the c axis perpendicular to the substrate. Scanning electron and atomic force microscopy indicate that the films had a rough surface and a compact structure consisting of small grains. Electroluminescence intensity of GaN:RE was significantly improved with postgrowth annealing. For GaN:Er films, after 800 °C annealing, the green emission brightness efficiency increased by ∼10×. © 2001 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors
68.37.Ps Atomic force microscopy (AFM)
61.72.Cc Kinetics of defect formation and annealing

12 W continuous-wave diode lasers at 1120 nm with InGaAs quantum wells

F. Bugge, G. Erbert, J. Fricke, S. Gramlich, R. Staske, H. Wenzel, U. Zeimer, and M. Weyers

Appl. Phys. Lett. 79, 1965 (2001); http://dx.doi.org/10.1063/1.1405812 (3 pages) | Cited 30 times

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Highly strained InGaAs quantum wells were grown by metalorganic vapor-phase epitaxy. By lowering the growth temperature to 530 °C, a maximum photoluminescence wavelength of 1192 nm was achieved. High-power diode lasers with a maximum lasing wavelength of 1175 nm were fabricated. A continuous-wave output power of 12 W at a heat-sink temperature of 25 °C was obtained at a lasing wavelength of 1120 nm. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells
42.60.Pk Continuous operation
68.65.Fg Quantum wells
81.07.St Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors

Another regime of operation for a 18.2 nm recombination laser using a capillary-discharged carbon plasma

K. Lee and D. Kim

Appl. Phys. Lett. 79, 1968 (2001); http://dx.doi.org/10.1063/1.1406554 (3 pages) | Cited 1 time

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Another regime of operation for the significant amplification of C VI Hα radiation in a capillary-discharged carbon plasma is proposed. This suggested regime of operation features the existence of gain at the axis of a capillary, the large gain region (several hundred micrometers in diameter), and the hollow electron density profile for the better guiding of the radiation being amplified. All these features help to overcome the previous problems and favor the high amplification of the radiation. © 2001 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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Structure and ordering of GaN quantum dot multilayers

V. Chamard, T. H. Metzger, E. Bellet-Amalric, B. Daudin, C. Adelmann, H. Mariette, and G. Mula

Appl. Phys. Lett. 79, 1971 (2001); http://dx.doi.org/10.1063/1.1403657 (3 pages) | Cited 15 times

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Grazing incidence x-ray techniques are used to characterize the structure of multilayered GaN quantum dots in an AlN matrix. For a dot lateral size of 170 Å, the values of the interdot vertical and lateral correlation lengths are 1500 and 250 Å, respectively. The presence of smaller quantum dots is observed only in the layers deposited first. The strain distribution in the multilayer is also investigated as a function of depth. Along the dot columns, the crystal lattice remains coherent, with elastic relaxation from the bottom to the top of the multilayer. © 2001 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)

Minority additive distributions in a ceramic metal-halide arc lamp using high-energy x-ray induced fluorescence

J. J. Curry, H. G. Adler, S. D. Shastri, and J. E. Lawler

Appl. Phys. Lett. 79, 1974 (2001); http://dx.doi.org/10.1063/1.1404401 (3 pages) | Cited 8 times

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X-ray induced fluorescence is used to measure the elemental densities of minority additives in a metal-halide arc contained inside a translucent ceramic envelope. A monochromatic x-ray beam from the Sector 1 Insertion Device beamline at the Advanced Photon Source is used to excite K-shell x-ray fluorescence in the constituents of a ceramic metal-halide arc lamp dosed with DyI3 and CsI. Fluorescence and scattered photons are collected by a cryogenic energy-resolving Ge detector. The high signal-to-noise spectra show strong fluorescence from Dy, Cs, and I, as well as elastic scattering from Hg. Radial distributions of the absolute elemental densities of Dy, Cs, and I are obtained. © 2001 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
42.72.Bj Visible and ultraviolet sources
52.70.La X-ray and γ-ray measurements
52.25.Vy Impurities in plasmas
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Carrier localization and the origin of luminescence in cubic InGaN alloys

P. R. C. Kent and Alex Zunger

Appl. Phys. Lett. 79, 1977 (2001); http://dx.doi.org/10.1063/1.1405003 (3 pages) | Cited 37 times

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The electronic structure and optical properties of cubic (nonpiezoelectric) InGaN are investigated using large scale atomistic empirical pseudopotential calculations. We find that (i) strong hole localization exists even in the homogeneous random alloy, with a preferential localization along the [1,1,0] In–N–In–N–In chains, (ii) even modest sized (<50 Å) indium rich quantum dots provide substantial quantum confinement and readily reduce emission energies relative to the random alloy by 200–300 meV, depending on size and composition, consistent with current photoluminescence, microscopy, and Raman data. The dual effects of alloy hole localization and localization of electrons and hole at intrinsic quantum dots are responsible for the emission characteristics of current grown cubic InGaN alloys. © 2001 American Institute of Physics.
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78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds
71.55.Eq III-V semiconductors

Effects of interdiffusion on the band alignment of GeSi dots

J. Wan, Y. H. Luo, Z. M. Jiang, G. Jin, J. L. Liu, Kang L. Wang, X. Z. Liao, and J. Zou

Appl. Phys. Lett. 79, 1980 (2001); http://dx.doi.org/10.1063/1.1405152 (3 pages) | Cited 14 times

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The interdiffusion effects on the band alignment of the GeSi dots embedded in Si matrix were studied by temperature- and excitation-power-dependent photoluminescence measurements. A different power-dependent behavior of the photoluminescence for the as-grown and the annealed samples was observed. It was suggested that the band alignments of the dots changed from type II to type I after annealing due to the Ge/Si interdiffusion. The decrease of the valence band offset, which was also induced by the Ge/Si interdiffusion, was observed from the temperature-dependent photoluminescence measurements. © 2001 American Institute of Physics.
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73.21.La Quantum dots
78.67.Hc Quantum dots
78.55.Hx Other solid inorganic materials
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Binding energy of vacancies to clusters formed in Si by high-energy ion implantation

R. Kalyanaraman, T. E. Haynes, O. W. Holland, H.-J. L. Gossmann, C. S. Rafferty, and G. H. Gilmer

Appl. Phys. Lett. 79, 1983 (2001); http://dx.doi.org/10.1063/1.1405814 (3 pages) | Cited 9 times

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Measurements of the binding energy (Eb) of vacancies to vacancy clusters formed in silicon following high-energy ion implantation are reported. Vacancy clusters were created by 2 MeV, 2×1015 cm−2 dose Si implant and annealing. To prevent recombination of the excess vacancies (Vex) with interstitials from the implant damage near the projected range (Rp), a Si-on-insulator substrate was used such that the Rp damage was separated from the Vex by the buried oxide (BOX). Two Vex regions were observed: one in the middle of the top Si layer (V1ex) and the other at the front Si/BOX interface (V2ex). The rates of vacancy evaporation were directly measured by Au labeling following thermal treatments at temperatures between 800 and 900 °C for times ranging from 600 to 1800 s. The rate of vacancy evaporation from V2ex was observed to be greater than from V1ex. The binding energy of vacancies to clusters in the middle of the silicon top layer was 3.2±0.2 eV as determined from the kinetics for vacancy evaporation. © 2001 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing

Direct measurement of the slow α-relaxation modes of a metallic liquid near the glass transition

Gerhard Wilde

Appl. Phys. Lett. 79, 1986 (2001); http://dx.doi.org/10.1063/1.1406145 (3 pages) | Cited 6 times

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Modulated-temperature calorimetry measurements on the bulk glass-forming Pd40Ni40P20 alloy yielded the complex specific heat response of the deeply undercooled melt near the static glass transition. The imaginary contributions to the complex signal give direct access to the spectrum of slow α-relaxation modes of the undercooled liquid state that are frozen in upon vitrification. The results are discussed with respect to the kinetics of the glass transition and compared to results obtained from static equilibrium measurements. © 2001 American Institute of Physics.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.25.Mv Liquid metals and alloys
61.43.Fs Glasses
65.20.-w Thermal properties of liquids

X-ray photoelectron spectroscopy study of irradiation-induced amorphizaton of Gd2Ti2O7

J. Chen, J. Lian, L. M. Wang, R. C. Ewing, and L. A. Boatner

Appl. Phys. Lett. 79, 1989 (2001); http://dx.doi.org/10.1063/1.1402647 (3 pages) | Cited 19 times

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The radiation-induced evolution of the microstructure of Gd2Ti2O7, an important pyrochlore phase in radioactive waste disposal ceramics and a potential solid electrolyte and oxygen gas sensor, has been characterized using transmission electron microscopy and x-ray photoelectron spectroscopy. Following the irradiation of a Gd2Ti2O7 single crystal with 1.5 MeV Xe+ ions at a fluence of 1.7×1014 Xe+/cm2, cross-sectional transmission electron microscopy revealed a 300-nm-thick amorphous layer at the specimen surface. X-ray photoelectron spectroscopy analysis of the Ti 2p and O 1s electron binding energy shifts of Gd2Ti2O7 before and after amorphization showed that the main results of ion-irradiation-induced disorder are a decrease in the coordination number of titanium and a transformation of the Gd–O bond. These features resemble those occurring in titanate glass formation, and they have implications for the chemical stability and electronic properties of pyrochlores subjected to displacive radiation damage. © 2001 American Institute of Physics.
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61.43.Er Other amorphous solids
61.82.Ms Insulators
61.80.Jh Ion radiation effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Misorientation-angle dependence of GaN layers grown on a-plane sapphire substrates by metalorganic chemical vapor deposition

T. Someya, K. Hoshino, and Y. Arakawa

Appl. Phys. Lett. 79, 1992 (2001); http://dx.doi.org/10.1063/1.1402636 (3 pages) | Cited 19 times

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High-quality GaN with smooth surface morphology has been grown on vicinal a-plane sapphire substrates by metalorganic chemical vapor deposition. The misorientation angles of vicinal a-plane sapphire substrates were changed systematically and the results were compared with the growth on exact a- and c-plane sapphire substrates. Surface morphology and crystalline qualities are found to be very sensitive to misorientation angles of a-plane sapphire substrates and the misorientation angle was optimized to be 0.25°. © 2001 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Origin of photoluminescence around 2.6–2.9 eV in silicon oxynitride

Takashi Noma, Kwang Soo Seol, Hiromitsu Kato, Makoto Fujimaki, and Yoshimichi Ohki

Appl. Phys. Lett. 79, 1995 (2001); http://dx.doi.org/10.1063/1.1405806 (3 pages) | Cited 14 times

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A broad photoluminescence (PL) around 2.6–2.9 eV is known to appear in hydrogenated silicon oxynitride. Although its origin was reported to be Si–N bonds, it is not so clear since the material contains hydrogen. In the present research, we have confirmed that the same PL appears in silicon oxynitride grown by nitriding of silicon dioxide. The depth profile of the PL intensity agrees with that of the nitrogen concentration. Furthermore, the emission spectrum, excitation spectrum, and decay constant of this PL agree with those of the PL observed in silicon nitride. Based on these results and theoretical discussion, the origin of the 2.6–2.9 eV PL is estimated to be Si–N bonds. © 2001 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.66.Nk Insulators

Composition, atomic transport, and chemical stability of ZrAlxOy ultrathin films deposited on Si(001)

J. Morais, E. B. O. da Rosa, R. P. Pezzi, L. Miotti, and I. J. R. Baumvol

Appl. Phys. Lett. 79, 1998 (2001); http://dx.doi.org/10.1063/1.1405808 (3 pages) | Cited 5 times

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The stability of a ZrAlxOy film sputtered on Si upon thermal annealing in vacuum or in O2 was investigated. X-ray diffraction indicated that the as-deposited film was amorphous and remained so after annealing. Rutherford backscattering, narrow nuclear resonance profiling, and low-energy ion scattering provided the average composition of the film and the depth distributions of different elements. Chemical analysis of these elements was accessed by x-ray photoelectron spectroscopy. Annealing in vacuum produced thickness inhomogeneities and/or transport of very small amounts of Si from the substrate into the overlying film, with formation of Si precipitates. Annealing in O2 led to oxygen exchange throughout the film, as well as Si transport in slightly higher amounts than in vacuum. Differently from the observed upon annealing in vacuum, Si was either incorporated into the Zr,Al–O framework or oxidized in SiO2. © 2001 American Institute of Physics.
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68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.43.Er Other amorphous solids
68.35.Fx Diffusion; interface formation
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.80.Jp Activation analysis and other radiochemical methods
64.75.-g Phase equilibria

Effects of B and C on the ordering of L10-CoPt thin films

H. Yamaguchi, O. Kitakami, S. Okamoto, Y. Shimada, K. Oikawa, and K. Fukamichi

Appl. Phys. Lett. 79, 2001 (2001); http://dx.doi.org/10.1063/1.1408605 (3 pages) | Cited 25 times

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We have investigated the effects of B and C on the ordering of L10-CoPt films and confirmed the following quite different role between B and C in CoPt. A small amount of B considerably decreases the temperature for ordering and is interstitially incorporated into L10-CoPt along its c axis due to the large negative heat of solutions with Co and Pt. X-ray photoelectron spectroscopy analyses have revealed that B atoms combine with Co and Pt. In contrast, C is not incorporated into the CoPt lattice due to its positive heat of solution, resulting in no decrease in the ordering temperature. The present results reveal that CoPt films containing a small amount of B are promising for high density recording media. © 2001 American Institute of Physics.
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75.50.Ss Magnetic recording materials
79.60.Dp Adsorbed layers and thin films
75.70.Ak Magnetic properties of monolayers and thin films

Influence of ultraviolet-light exposure on electron-beam written gratings in amorphous As–Se thin films coated with different metals

Olli Nordman, Nina Nordman, and Valfrid Pashkevich

Appl. Phys. Lett. 79, 2004 (2001); http://dx.doi.org/10.1063/1.1405810 (3 pages)

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Gratings were written in amorphous As–Se thin films using electron-beam lithography. Films were coated with different metals. Electrons caused the change in the refractive index, which could be analyzed through the diffraction pattern of the grating reading laser beam. The refractive index change was found to be dependent on the overcoated metal layer. Ultraviolet (UV) light exposure was applied on investigated films before and after the grating writing. In some cases the exposure given after the grating writing enhanced greatly the diffraction efficiency. Results suggest the use of these thin films as UV-light detectors. © 2001 American Institute of Physics.
Show PACS
42.79.Dj Gratings
78.66.Jg Amorphous semiconductors; glasses
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.88.+h Environmental and radiation effects on optical elements, devices, and systems
61.82.Fk Semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Wc Optical coatings
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.60.Gz Photodetectors (including infrared and CCD detectors)
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