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5 Feb 2001

Volume 78, Issue 6, pp. 685-846

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Near-field images of the AgOx-type super-resolution near-field structure

Wei-Chih Liu, Cheng-Yen Wen, Kuei-Hsien Chen, Wei Chih Lin, and Din Ping Tsai

Appl. Phys. Lett. 78, 685 (2001); http://dx.doi.org/10.1063/1.1345832 (3 pages) | Cited 32 times

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As a promising disk structure for ultrahigh density optical data storage, super-resolution near-field structure of AgOx type has been studied by the tapping-mode tuning-fork near-field scanning optical microscope as well as the transmission electron microscope. This structure presents strong near-field intensity enhancement and nonlinear optical effect, compared with the ordinary material. Numerical calculations confirm that the localized surface plasmon and the nonuniform material structures are the main causes for these unusual characteristics. © 2001 American Institute of Physics.
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42.79.Vb Optical storage systems, optical disks
68.37.Uv Near-field scanning microscopy and spectroscopy
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.68.+m Optical properties of surfaces

Photorefractive chiral smectic A phases

R. Termine, B. C. De Simone, and A. Golemme

Appl. Phys. Lett. 78, 688 (2001); http://dx.doi.org/10.1063/1.1345824 (3 pages) | Cited 6 times

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We present results of the photorefractive properties of a chiral smectic A liquid-crystalline phase. In our approach, the mesophase is sandwiched between two photoconducting layers. In contrast to the effect due to the dielectric anisotropy typical of nematic phases, the refractive-index modulation is due to the electroclinic effect. We measured the grating spacing and the field dependence of the gain coefficient and obtained a net two-beam coupling gain of 600 cm−1 at 35 V/μm. © 2001 American Institute of Physics.
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42.70.Df Liquid crystals
42.70.Ln Holographic recording materials; optical storage media
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
78.20.Jq Electro-optical effects
42.40.Ht Hologram recording and readout methods
42.40.Eq Holographic optical elements; holographic gratings

Strong luminescence from Tamm states in modulation-doped superlattices

A. B. Henriques

Appl. Phys. Lett. 78, 691 (2001); http://dx.doi.org/10.1063/1.1346627 (3 pages) | Cited 4 times

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Calculations are presented for the photoluminescence spectrum of InP/In0.53Ga0.47As superlattices doped with Si. When doping is confined to the inner barriers, the photoluminescence is dominated by transitions between Tamm states in the electron and valence bands, which contribute with an optical band at energies higher than the In0.53Ga0.47As band gap. These results are in good agreement with experimental observations. © 2001 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
73.21.Cd Superlattices

Gratings in indium oxide film overlayers on ion-exchanged waveguides by excimer laser micromachining

S. Pissadakis, L. Reekie, M. N. Zervas, J. S. Wilkinson, and G. Kiriakidis

Appl. Phys. Lett. 78, 694 (2001); http://dx.doi.org/10.1063/1.1345836 (3 pages) | Cited 6 times

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Relief Bragg gratings were imprinted by 248 nm interferometric excimer laser ablation on potassium ion-exchanged channel waveguides in BK-7 glass overlaid with a thin high-index InOx film. Using five pulses of energy density 60 mJ/cm2, a spectral transmittance notch of depth 66% and ΔλFWHM<0.1 nm was obtained at 1547 nm in the TE polarization for a waveguide having a nominal width of 8 μm and a 135-nm-thick InOx overlayer. In waveguides coated with 100 nm InOx, with widths increasing from 3 to 8 μm, the reflection wavelength shifted by 0.12 nm/μm and the reflectivity increased monotonically. © 2001 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Dj Gratings
42.82.Et Waveguides, couplers, and arrays
78.66.Li Other semiconductors
42.62.-b Laser applications

Influence of disorder and a parallel magnetic field on a quantum cascade laser

V. M. Apalkov and Tapash Chakraborty

Appl. Phys. Lett. 78, 697 (2001); http://dx.doi.org/10.1063/1.1343495 (3 pages) | Cited 5 times

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The luminescence spectra of a quantum cascade laser (QCL) in a strong magnetic field is influenced significantly by the presence of disorder (charged or neutral) in the system. An externally applied magnetic field parallel to the electron plane causes a redshift of the luminescence peak in the absence of any disorder potential. Our results indicate that the disorder potential tends to cancel that redshift and causes a rapid decrease of the luminescence peak. A similar behavior was observed in a recent experiment on a QCL in a parallel magnetic field by S. Blaser, L. Diehl, M. Beck, and J. Faist [Physica E 7, 33 (2000)]. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.20.Ls Magneto-optical effects
78.55.-m Photoluminescence, properties and materials

Efficient molecular photorefractive materials based on methine dyes

Liming Wang, Man-Kit Ng, and Luping Yu

Appl. Phys. Lett. 78, 700 (2001); http://dx.doi.org/10.1063/1.1347025 (3 pages) | Cited 19 times

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This letter reports a series of molecular materials that shows efficient photorefractive effect. The materials which consist of monolithic methine dye molecules can form amorphous films. A net photorefractive gain of 215 cm−1 and a diffraction efficiency of 87.6% at a semiconductor laser wavelength of 780 nm are observed. These materials are the simplest molecular materials and possess the best photorefractive performances. Due to the large photorefractive effect, optical self-defocusing and instability of the laser beam are observed in these materials when the applied electric field is above a threshold. © 2001 American Institute of Physics.
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42.70.Gi Light-sensitive materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
72.40.+w Photoconduction and photovoltaic effects

Optically induced pulse delay in a solid-state Raman amplifier

Kijoon Lee and Nabil M. Lawandy

Appl. Phys. Lett. 78, 703 (2001); http://dx.doi.org/10.1063/1.1347009 (3 pages) | Cited 27 times

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The pump-induced group velocity reduction of subnanosecond pulses is calculated and measured in a Ba(NO3)2 solid-state Raman amplifier. 1.197 μm probe pulses with 90 ps duration were generated using a Raman-shifted mode-locked and Q-switched Nd:YAG laser, and propagated through a Ba(NO3)2 crystal synchronously pumped by 7-ns-long 1.06 μm pulses. The time delay of the pulse peak was measured with varying pump intensity and was compared with theoretical calculation up to the point where amplified spontaneous Raman emission becomes dominant. The maximum time delay was found to be 105 ps. © 2001 American Institute of Physics.
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42.55.Ye Raman lasers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
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Extraction of ions from the matrix sheath in ablation-plasma ion implantation

Bo Qi, Y. Y. Lau, and R. M. Gilgenbach

Appl. Phys. Lett. 78, 706 (2001); http://dx.doi.org/10.1063/1.1343842 (3 pages) | Cited 4 times

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A simple one-dimensional theory is presented to assess the implantation of ions from the ion matrix sheath (IMS) in an ablated plasma plume that is approaching a negatively biased substrate. Under the assumption that the plume geometry, the electron and ion density distributions, and the potential distribution are frozen during the IMS extraction, the implanted ion current is calculated as a function of time for various substrate-plume separations. This model accurately recovers Lieberman’s classic results when the plume front is initially in contact with the substrate. © 2001 American Institute of Physics.
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52.77.Dq Plasma-based ion implantation and deposition
61.80.Jh Ion radiation effects
52.38.Mf Laser ablation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
52.40.Kh Plasma sheaths

Excitation of a microdischarge with a reverse-biased pn junction

C. J. Wagner, S.-J. Park, and J. G. Eden

Appl. Phys. Lett. 78, 709 (2001); http://dx.doi.org/10.1063/1.1345838 (3 pages) | Cited 14 times

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Excitation of cylindrical microdischarges, 300–360 μm in diameter, by a reverse-biased, Si pn junction has been demonstrated. Devices fabricated from commercial diodes have been operated with Ne gas pressures in the 200–700 Torr range and dc voltages as low as 120 V. For a Ne gas pressure of 700 Torr, the wavelength-integrated (300–800 nm) output power—emitted into a solid angle of ∼ 6×10−2 sr—of a 360-μm-diam device is 48±1 μW for an operating current and voltage of 5.7±0.1 mA and 134 V, respectively. This hybrid solid state/gas device represents the demonstration of the generation of a gas discharge by a pn junction and lends itself to the fabrication of large arrays. © 2001 American Institute of Physics.
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52.80.Hc Glow; corona
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Kk Junction diodes
42.72.Bj Visible and ultraviolet sources
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Molecular-beam epitaxial growth and surface characterization of GaAs(311)B

Z. M. Wang, L. Däweritz, and K. H. Ploog

Appl. Phys. Lett. 78, 712 (2001); http://dx.doi.org/10.1063/1.1337632 (3 pages) | Cited 16 times

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Reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) are used to study the surface and growth of GaAs (311)B. The RHEED pattern reveals a lateral periodicity of 3.2 nm along the [01math] direction, which is confirmed in real space by STM images. Pronounced RHEED intensity oscillations during the homoepitaxial growth on GaAs(311)B were observed in a wide substrate temperature range. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.55.A- Nucleation and growth
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.05.Ea III-V semiconductors

Influence of crystallite size distribution on the micro-Raman analysis of porous Si

Md. N. Islam and Satyendra Kumar

Appl. Phys. Lett. 78, 715 (2001); http://dx.doi.org/10.1063/1.1343494 (3 pages) | Cited 34 times

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First-order Raman spectra from nanocrystalline semiconductors reflect the influence of crystallite sizes on the Raman shifts and line shapes. A Gaussian distribution in crystallite sizes is explicitly included to calculate the Raman spectra of porous silicon. Several porous-silicon samples were prepared using electrochemical anodization, and Raman as well as photoluminescence measurements were carried out on the same spots using a micro-Raman probe. The size distribution obtained from fitting the Raman data using our procedure is able to predict the photoluminescence accurately in the quantum-confinement models. © 2001 American Institute of Physics.
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78.30.Am Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
78.55.Mb Porous materials
81.05.Rm Porous materials; granular materials
61.46.-w Structure of nanoscale materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
81.65.-b Surface treatments

Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles

J. A. Eastman, S. U. S. Choi, S. Li, W. Yu, and L. J. Thompson

Appl. Phys. Lett. 78, 718 (2001); http://dx.doi.org/10.1063/1.1341218 (3 pages) | Cited 111 times

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It is shown that a “nanofluid” consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol % Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity. © 2001 American Institute of Physics.
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65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
66.25.+g Thermal conduction in nonmetallic liquids
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

Fabrication of CaS:Pb blue phosphor by incorporating dimeric Pb2+ luminescent centers

Sun Jin Yun, Yong Shin Kim, and Sang-Hee Ko Park

Appl. Phys. Lett. 78, 721 (2001); http://dx.doi.org/10.1063/1.1343478 (3 pages) | Cited 12 times

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The CaS:Pb phosphor emitting blue electroluminescence (EL) induced by dimeric Pb2+ luminescent centers was deposited using the controlled atomic layer deposition technique. The effect of the incorporation method and concentration of Pb2+ ions on the color of high luminance CaS:Pb phosphor was investigated at the deposition temperatures of 350 and 400 °C. The blue EL emission at 440–445 nm could be maintained with the Pb concentration ranging from 0.6 to 2.5 mol % contrary to the earlier works that had demonstrated very sensitive dependence of color on Pb2+ concentration. The selective incorporation of dimeric Pb2+ ions was attributed to the reactivity of tetraethyl lead as Pb precursor as well as the controlled deposition technique. © 2001 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.79.Wc Optical coatings
78.66.Li Other semiconductors
68.55.A- Nucleation and growth
78.60.Fi Electroluminescence

Raman scattering studies on single-crystalline bulk AlN under high pressures

M. Kuball, J. M. Hayes, A. D. Prins, N. W. A. van Uden, D. J. Dunstan, Ying Shi, and J. H. Edgar

Appl. Phys. Lett. 78, 724 (2001); http://dx.doi.org/10.1063/1.1344567 (3 pages) | Cited 48 times

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We report on the Raman analysis of wurtzite single-crystalline bulk AlN under hydrostatic pressures up to 10 GPa. The pressure dependence of the AlN phonon frequencies was investigated. Mode Grüneisen parameters of 1.39, 1.57, 1.71, 0.93, and 1.26 were determined for the A1 (TO), E1 (TO), E2 (high), A1 (LO), and the quasi-longitudinal optical phonons, respectively. Recent theoretical calculations underestimate the pressure-induced frequency shift of the AlN phonons by about 20%–30%. Mode Grüneisen parameters of AlN were compared to those of GaN. © 2001 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
62.50.-p High-pressure effects in solids and liquids
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Maskless epitaxial lateral overgrowth of GaN layers on structured Si(111) substrates

A. Strittmatter, S. Rodt, L. Reißmann, D. Bimberg, H. Schröder, E. Obermeier, T. Riemann, J. Christen, and A. Krost

Appl. Phys. Lett. 78, 727 (2001); http://dx.doi.org/10.1063/1.1347013 (3 pages) | Cited 41 times

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GaN layers are laterally overgrown by metalorganic chemical vapor deposition on structured Si(111) substrates in a single growth process. The substrates are structured with parallel grooves along the Si 〈1–10〉 or perpendicular to the Si 〈1–10〉 direction by standard photolithography and subsequent dry etching. Due to the anisotropic chemical dry etch process, the remaining Si ridges are underetched. The GaN layer grows nearly exclusively on the bottom of the grooves and on the top of the ridges between the grooves. These two growth fronts are completely separated from each other. As a consequence, the GaN layer growing from the ridge area between grooves can extend over the grooves. This process is similar to the so called pendeo-epitaxy process, but is completely mask free during growth and does not require any growth interruption. The improvement of the crystalline and the optical quality of the GaN layer is demonstrated by atomic force microscopy and cathodoluminescence spectroscopy. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Cf Surface cleaning, etching, patterning
78.60.Hk Cathodoluminescence, ionoluminescence

Structural modification of single-axis-oriented yttria-stabilized-zirconia films under zirconium ion bombardment

A. A. Voevodin, J. G. Jones, and J. S. Zabinski

Appl. Phys. Lett. 78, 730 (2001); http://dx.doi.org/10.1063/1.1345823 (3 pages) | Cited 12 times

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Crystal size and orientation control of yttria-stabilized-zirconia (YSZ) films produced by pulsed-laser deposition under zirconium-ion bombardment are reported. A structure development mechanism is proposed based on the correlation between ablated plasma chemistry, velocity distributions of atomic and molecular species in the plasma, bombardment energy, time, incidence angle, film crystal size, and orientation. A near-room-temperature growth of single-axis-oriented YSZ films with (002) texture on randomly oriented polycrystalline substrates is demonstrated. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
61.80.Jh Ion radiation effects
61.82.Ms Insulators

Hanle effect measurements of spin lifetimes in InAs self-assembled quantum dots

R. J. Epstein, D. T. Fuchs, W. V. Schoenfeld, P. M. Petroff, and D. D. Awschalom

Appl. Phys. Lett. 78, 733 (2001); http://dx.doi.org/10.1063/1.1344565 (3 pages) | Cited 31 times

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Transverse spin lifetimes of spin-polarized photogenerated carriers in InAs self-assembled quantum dots are extracted from the depolarization of their photoluminescence in a magnetic field perpendicular to the spin (the Hanle effect). Hanle measurements on a series of samples reveal that the dot dimensions influence the spin lifetime and its dependence on temperature. The spin lifetime as a function of excitation intensity is qualitatively distinct for carrier spins created in the GaAs host as compared to in the InAs wetting layer. © 2001 American Institute of Physics.
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72.25.Dc Spin polarized transport in semiconductors
73.21.La Quantum dots
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
73.63.Kv Quantum dots

Fast through-bond diffusion of nitrogen in silicon

Peter A. Schultz and Jeffrey S. Nelson

Appl. Phys. Lett. 78, 736 (2001); http://dx.doi.org/10.1063/1.1345828 (3 pages) | Cited 15 times

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We report first-principles total energy calculations of interaction of nitrogen in silicon with silicon self-interstitials. Substitutional nitrogen captures a silicon interstitial with 3.5 eV binding energy forming a 〈100〉 split interstitial ground-state geometry, with the nitrogen forming three bonds. The low-energy migration path is through a bond bridge state having two bonds. Fast diffusion of nitrogen occurs through a pure interstitialcy mechanism: the nitrogen never has less than two bonds. Near-zero formation energy of the nitrogen interstitialcy with respect to the substitutional rationalizes the low solubility of substitutional nitrogen in silicon. © 2001 American Institute of Physics.
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66.30.J- Diffusion of impurities
71.55.Cn Elemental semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.J- Point defects and defect clusters
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Nc Total energy and cohesive energy calculations

Defect-induced tetragonalization of the orthorhombic TiSi2 C49 phase: X-ray diffraction and first principles calculations

F. La Via, M. G. Grimaldi, D. B. Migas, and Leo Miglio

Appl. Phys. Lett. 78, 739 (2001); http://dx.doi.org/10.1063/1.1345829 (3 pages) | Cited 5 times

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We discuss the rather scattered predictions on the orthorhombic lattice parameters for the C49 TiSi2 phase, which are reported in the literature. New and accurate x-ray diffraction measurements and ab initio calculations are presented. Both agree in indicating that the density is higher than the one commonly assumed and it is close to the stable C54 phase. An unexpected tetragonalization of the orthorhombic cell has been observed and the theoretical analysis shows that this phenomenon could be originated by the massive presence of stacking faults. © 2001 American Institute of Physics.
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61.66.Fn Inorganic compounds
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
61.72.Nn Stacking faults and other planar or extended defects
71.15.Nc Total energy and cohesive energy calculations

Sharp band edge photoluminescence of high-purity CuInS2 single crystals

Kenji Yoshino, Tetsuo Ikari, Sho Shirakata, Hideto Miyake, and Kazumasa Hiramatsu

Appl. Phys. Lett. 78, 742 (2001); http://dx.doi.org/10.1063/1.1345802 (3 pages) | Cited 31 times

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Temperature-dependent photoluminescence measurements were carried out between 8 and 300 K on CuInS2 single crystals grown by a traveling heater method. Ten distinct peaks were present in the near-band edge region. Four unknown peaks, observed at 8 K, were found to be due to bound exciton emission. Moreover, the luminescence remained stable up to room temperature. © 2001 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
71.35.Gg Exciton-mediated interactions
71.55.Ht Other nonmetals

Carrier-type reversal in Pb–Ge–Se glasses: Photopyroelectric measurements of thermal conductivity and heat capacity

J. Philip, R. Rajesh, and C. Preethy Menon

Appl. Phys. Lett. 78, 745 (2001); http://dx.doi.org/10.1063/1.1345839 (3 pages) | Cited 4 times

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The thermal conductivity and heat capacity of Pb modified Ge–Se glasses, Pb20GexSe80−x (x = 17–24) and PbyGe42−ySe58 (y = 0–20), which exhibit carrier-type reversal from p type to n type at specific compositions, have been measured simultaneously by the photopyroelectric technique. The thermal conductivity as well as the heat capacity show anomalous variations at the compositions at which carrier-type reversals are reported to occur in these glasses. The results are explained in terms of the enhancement in electron concentration during p- to n-type changeover in these materials. © 2001 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
65.40.Ba Heat capacity
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
72.20.Fr Low-field transport and mobility; piezoresistance
61.43.Fs Glasses

Structural changes during annealing of GaInAsN

Sarah Kurtz, J. Webb, L. Gedvilas, D. Friedman, J. Geisz, J. Olson, R. King, D. Joslin, and N. Karam

Appl. Phys. Lett. 78, 748 (2001); http://dx.doi.org/10.1063/1.1345819 (3 pages) | Cited 128 times

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The alloy GaInAsN has great potential as a lower-band-gap material lattice matched to GaAs, but there is little understanding of what causes its poor optoelectronic properties and why these improve with annealing. This study provides information about the structural changes that occur when GaInAsN is annealed. The Fourier transform infrared spectra exhibit two primary features: a triplet at ∼470 cm−1 (Ga–N stretch) and two or three bands at ∼3100 cm−1 (N–H stretch). The change in the Ga–N stretch absorption can be explained if the nitrogen environment is converted from NGa4 to NInGa3 after annealing. The N–H stretch is also changed after annealing, implying a second, and unrelated, structural change. © 2001 American Institute of Physics.
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61.66.Fn Inorganic compounds
78.30.Fs III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
63.20.-e Phonons in crystal lattices
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Improved performance of amorphous silicon thin film transistors by cyanide treatment

Hemantkumar N. Aiyer, Daikichi Nishioka, Nobuyuki Matsuki, Hiroyuki Shinno, V. P. S. Perera, Toyohiro Chikyow, Hikaru Kobayashi, and Hideomi Koinuma

Appl. Phys. Lett. 78, 751 (2001); http://dx.doi.org/10.1063/1.1344230 (3 pages) | Cited 3 times

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We have examined the impact of a simple, wet chemical postgrowth treatment of “immersing in KCN solution” on the performance of inverted staggered amorphous silicon n-channel thin film transistors. Results show that the cyanide treatment significantly improves the overall transistor performance by the elimination of defect states. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
81.65.-b Surface treatments

Effect of buffer layer preparation on GaN epilayers grown by gas-source molecular-beam epitaxy

V. Bousquet, J. Heffernan, J. Barnes, and S. Hooper

Appl. Phys. Lett. 78, 754 (2001); http://dx.doi.org/10.1063/1.1344227 (3 pages) | Cited 3 times

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Using gas-source molecular-beam epitaxy, and ammonia as a source of nitrogen, we have investigated the effect of buffer layer preparation on the electrical and optical properties of GaN epilayers. It is found that the buffer layer thickness and buffer anneal time have a dramatic effect on the Hall mobility and the background carrier density in the layers. With an optimized buffer layer, we have achieved mobility of ∼190 cm2/V s and have correlated this with a defect density as low as 2.1×109 cm−2 in the best layers. The variation of the intensity of defect related lines in photoluminescence spectra has been used to confirm the decrease of the defect density with increasing mobility in these layers. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.Cc Kinetics of defect formation and annealing

Properties of carbon-doped GaN

H. Tang, J. B. Webb, J. A. Bardwell, S. Raymond, Joseph Salzman, and C. Uzan-Saguy

Appl. Phys. Lett. 78, 757 (2001); http://dx.doi.org/10.1063/1.1345816 (3 pages) | Cited 38 times

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The properties of carbon-doped GaN epilayers grown by molecular-beam epitaxy have been studied by temperature-dependent resistivity, Hall-effect measurements, x-ray diffraction, and by photoluminescence spectroscopy. Carbon doping was found to render the GaN layers highly resistive (>108 Ω cm) and quench the band edge excitonic emissions. Yellow luminescence is still present in carbon-doped GaN layers. The highly resistive state is interpreted as being caused by direct compensation by the carbon acceptors and by the consequently enhanced potential barrier at the subgrain boundaries. Evidence of dislocations joining to form potential barriers along the subgrain boundaries was observed in photoassisted wet etching experiments on electrically conducting GaN layers. GaN films grown on insulating carbon-doped base layers are of excellent transport and optical properties. © 2001 American Institute of Physics.
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73.61.Ey III-V semiconductors
71.55.Eq III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
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