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12 Jul 2004

Volume 85, Issue 2, pp. 161-347

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 341 (2004); http://dx.doi.org/10.1063/1.1772854 (3 pages)

Xiangdong Zhang and Zhengyou Liu
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White beam x-ray waveguide optics

A. Jarre, T. Salditt, T. Panzner, U. Pietsch, and F. Pfeiffer

Appl. Phys. Lett. 85, 161 (2004); http://dx.doi.org/10.1063/1.1768309 (3 pages) | Cited 3 times

Online Publication Date: 8 July 2004

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We report a white beam x-ray waveguide (WG) experiment. A resonant beam coupler x-ray waveguide (RBC) is used simultaneously as a broad bandpass (or multibandpass) monochromator and as a beam compressor. We show that, depending on the geometrical properties of the WG, the exiting beam consists of a defined number of wavelengths which can be shifted by changing the angle of incidence of the white x-ray synchrotron beam. The characteristic far-field pattern is recorded as a function of exit angle and energy. This x-ray optical setup may be used to enhance the intensity of coherent x-ray WG beams since the full energetic acceptance of the WG mode is transmitted.
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41.50.+h X-ray beams and x-ray optics
41.85.Si Particle beam collimators, monochromators
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
07.85.Qe Synchrotron radiation instrumentation
42.79.Gn Optical waveguides and couplers

Generation and detection of ultrabroadband terahertz radiation using photoconductive emitters and receivers

Y. C. Shen, P. C. Upadhya, H. E. Beere, E. H. Linfield, A. G. Davies, I. S. Gregory, C. Baker, W. R. Tribe, and M. J. Evans

Appl. Phys. Lett. 85, 164 (2004); http://dx.doi.org/10.1063/1.1768313 (3 pages) | Cited 32 times

Online Publication Date: 8 July 2004

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We report the coherent generation and detection of ultrabroadband terahertz (THz) radiation using low-temperature-grown GaAs photoconductive antennas as both emitters and receivers. THz radiation with frequency components over 15 THz was obtained, the highest reported for a THz time-domain system based on photoconductive antennas. Such a system has a smooth spectral distribution between 0.3 and 7.5 THz, ideal for spectroscopic applications. In addition, sharp spectral features at 8.0 and 8.8 THz were observed, and explained in terms of optical phonon resonances in the photoconductive antennas.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.72.Ai Infrared sources
84.40.Ba Antennas: theory, components and accessories

Room temperature operation of InAs∕AlSb quantum cascade lasers

R. Teissier, D. Barate, A. Vicet, C. Alibert, A. N. Baranov, X. Marcadet, C. Renard, M. Garcia, C. Sirtori, D. Revin, and J. Cockburn

Appl. Phys. Lett. 85, 167 (2004); http://dx.doi.org/10.1063/1.1768306 (3 pages) | Cited 32 times

Online Publication Date: 8 July 2004

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The room temperature operation of InAs∕AlSb quantum cascade lasers is reported. The structure, grown by molecular beam epitaxy on an InAs substrate, is based on a vertical transition design and a low loss n+-InAs plasmon enhanced waveguide. The lasers emitting near 4.5 μm operate in pulse regime up to 300 K. The threshold current density of 3.18-mm-long lasers is 1.5 kA∕cm2 at 83 K and 9 kA∕cm2 at 300 K.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Simplified nonplanar wafer bonding for heterogeneous device integration

Jon Geske, John E. Bowers, and Anton Riley

Appl. Phys. Lett. 85, 170 (2004); http://dx.doi.org/10.1063/1.1771462 (3 pages)

Online Publication Date: 8 July 2004

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We demonstrate a simplified nonplanar wafer bonding technique for heterogeneous device integration. The improved technique can be used to laterally integrate dissimilar semiconductor device structures on a lattice-mismatched substrate. Using the technique, two different InP-based vertical-cavity surface-emitting laser active regions have been integrated onto GaAs without compromising the quality of the photoluminescence. Experimental and numerical simulation results are presented.
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85.30.De Semiconductor-device characterization, design, and modeling

Emission of electromagnetic radiation by coherent vibrational waves in stimulated Raman scattering

Michael P. Hasselbeck, L. A. Schlie, and D. Stalnaker

Appl. Phys. Lett. 85, 173 (2004); http://dx.doi.org/10.1063/1.1769588 (3 pages) | Cited 5 times

Online Publication Date: 8 July 2004

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Electromagnetic radiation is emitted by the vibrational and collective modes of an opaque solid as the result of impulsive stimulated Raman scattering. Raman scattering of near-infrared femtosecond laser pulses produces coherent longitudinal optical phonon and plasmon oscillations in the semiconductor InSb. These oscillations radiate into free space at THz frequencies and are directly detected. The THz spectra exhibit features consistent with Raman selection rules including interference of allowed and forbidden Raman scattering.
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78.30.Fs III-V and II-VI semiconductors
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
63.20.kk Phonon interactions with other quasiparticles
78.70.-g Interactions of particles and radiation with matter

Three-dimensional patterned media for ultrahigh-density optical memory

Masaharu Nakano, Takaaki Kooriya, Takashi Kuragaito, Chikara Egami, Yoshimasa Kawata, Masaaki Tsuchimori, and Osamu Watanabe

Appl. Phys. Lett. 85, 176 (2004); http://dx.doi.org/10.1063/1.1771800 (3 pages) | Cited 18 times

Online Publication Date: 8 July 2004

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We report a recording medium in which a three-dimensional nanoscale structure can be photofabricated for multilayered optical memory using a two-photon process. By fabricating the structures in the medium, we can control the shape of recorded bits and, in effect, their spatial frequency distribution. We succeeded in recording bits with a 0.5 μm interval in any particular plane and 2.0 μm interval between successive layers. Thus, storage density of 2.0 Tbits∕cm3 is achieved.
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42.79.Vb Optical storage systems, optical disks

Third-order optical autocorrelator for time-domain operation at telecommunication wavelengths

G. Ramos-Ortiz, M. Cha, S. Thayumanavan, J. C. Mendez, S. R. Marder, and B. Kippelen

Appl. Phys. Lett. 85, 179 (2004); http://dx.doi.org/10.1063/1.1771809 (3 pages) | Cited 7 times

Online Publication Date: 8 July 2004

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We report on amorphous organic thin films that exhibit efficient third-harmonic generation at telecommunication wavelengths. At 1550 nm, micrometer-thick samples generate up to 17 μW of green light with input power of 250 mW delivered by an optical parametric oscillator. This high conversion efficiency is achieved without phase matching or cascading of quadratic nonlinear effects. With these films, we demonstrate a low-cost, sensitive third-order autocorrelator that can be used in the time-frequency domain.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Yj Optical parametric oscillators and amplifiers
42.79.Hp Optical processors, correlators, and modulators
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Coupled surface plasmon-polariton mediated photoluminescence from a top-emitting organic light-emitting structure

S. Wedge, J. A. E. Wasey, W. L. Barnes, and I. Sage

Appl. Phys. Lett. 85, 182 (2004); http://dx.doi.org/10.1063/1.1772516 (3 pages) | Cited 45 times

Online Publication Date: 8 July 2004

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We report strong photoluminescence from a top-emitting organic light-emitting structure where emission takes place through a thin (55 nm) silver film. We show that this emission is mediated via coupled surface plasmon-polariton modes. Our results show that the addition of a dielectric grating to otherwise planar structures, such as surface-emitting organic light-emitting diodes, may offer a way to increase the external efficiency of top-emitting organic light-emitting diodes.
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85.60.Jb Light-emitting devices
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.-m Photoluminescence, properties and materials

Near-infrared laser emission from luminescent plastic waveguides

Takeyuki Kobayashi, Jean-Baptiste Savatier, Grace Jordan, Werner J. Blau, Yasuhiro Suzuki, and Toshikuni Kaino

Appl. Phys. Lett. 85, 185 (2004); http://dx.doi.org/10.1063/1.1772524 (3 pages) | Cited 21 times

Online Publication Date: 8 July 2004

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We have demonstrated optical gain and laser emission in multimoded plastic waveguides containing a near-infrared-emitting compound, 2-(6-(4-dimethylaminophenyl)-2,4-neopentylene-1,3,5-hexatrienyl)-3-methyl-benzothiazolium perchlorat. The poly(1-vinyl-2-pyrrolidone)-base planar waveguides, 1 cm in length and 50 μm in thickness, doped with 0.5 wt % of the compound have exhibited lasing at 820 nm under transverse nanosecond photoexcitation at 532 nm. Optical feedback is provided by the 4% reflective facets of the cleaved waveguide edges. The threshold for lasing is found to be 128±30 μJ∕cm2 (25.5±5.9 kW∕cm2). Gain spectroscopy has shown a moderate net modal gain of 2.6±0.3 cm−1 (11.3±1.3 dB∕cm) at 820 nm for the pump fluence of 115 μJ∕cm2 (23.1 kW∕cm2). Our results will open the door to the study and development of compact plastic waveguide lasers and amplifiers operating in the near-infrared region.
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42.79.Gn Optical waveguides and couplers
42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
42.70.Jk Polymers and organics
78.55.Kz Solid organic materials

Efficient generation of red light by frequency doubling in a periodically-poled nearly-stoichiometric LiTaO3 crystal

X. P. Hu, X. Wang, J. L. He, Y. X. Fan, S. N. Zhu, H. T. Wang, Y. Y. Zhu, and N. B. Ming

Appl. Phys. Lett. 85, 188 (2004); http://dx.doi.org/10.1063/1.1772525 (3 pages) | Cited 8 times

Online Publication Date: 8 July 2004

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An efficient generation of red light in a periodically-poled nearly-stoichiometric LiTaO3 (PPSLT) by extracavity single-pass frequency doubling of a diode-pumped, Q-switched Nd:YVO4 laser at 1342 nm was realized. An average power of 1.4 W of the 671 nm red light is obtained at the fundamental power of ∼2.8 W with the conversion efficiency of 50%. The high conversion efficiency and steady output of red light indicate that the thick PPSLT is a competitive candidate for frequency conversion in order to construct a compact all-solid-state red laser.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Strong enhancement of terahertz radiation from semiconductor surfaces using MgO hemispherical lens coupler

M. Nakajima, K. Uchida, M. Tani, and M. Hangyo

Appl. Phys. Lett. 85, 191 (2004); http://dx.doi.org/10.1063/1.1772861 (3 pages) | Cited 11 times

Online Publication Date: 8 July 2004

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We report an enhancement of terahertz radiation power from InAs surfaces excited by ultrashort laser pulses using an MgO hemispherical lens coupler. The power of the terahertz radiation from the InAs surface with the MgO lens coupler is 50 times larger than that from the InAs surface without the MgO lens coupler. The enhancement is explained mainly by the increase of the transmission efficiency of the THz wave from InAs to free space.
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78.45.+h Stimulated emission
72.40.+w Photoconduction and photovoltaic effects
79.20.Ds Laser-beam impact phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources

Efficient light absorption in metal–semiconductor–metal nanostructures

Stéphane Collin, Fabrice Pardo, Roland Teissier, and Jean-Luc Pelouard

Appl. Phys. Lett. 85, 194 (2004); http://dx.doi.org/10.1063/1.1771467 (3 pages) | Cited 32 times

Online Publication Date: 8 July 2004

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A nanoscale metal–semiconductor grating is proposed for efficient and ultrafast photodetection. Theoretical and experimental results of efficient absorption in nanoscopic semiconductor wires are presented. The strong confinement of light in subwavelength metal–semiconductor gratings is achieved by Fabry–Pérot resonances involving vertical transverse magnetic surface-plasmon waves and transverse electric guided waves. Photodetectors have been fabricated with 40×100 nm cross sections of Ag and GaAs wires. The reflectivity and photocurrent mesurements are in good agreement with theoretical estimates.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.40.Sx Metal-semiconductor-metal structures
72.40.+w Photoconduction and photovoltaic effects
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Effective-mean-field approach for macroscopic elastic constants of composites

Masakazu Tane and Tetsu Ichitsubo

Appl. Phys. Lett. 85, 197 (2004); http://dx.doi.org/10.1063/1.1769587 (3 pages) | Cited 10 times

Online Publication Date: 8 July 2004

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We propose an evaluation method for macroscopic elastic constants of composites, which is called the effective-mean-field method. The method is based on Mori–Tanaka’s mean-field (MTMF), and the effective-medium approximation methods, in which complex elastic fields disturbed by many inclusions are replaced by the average fields of a virtually homogenized composite, and the MTMF formulae are utilized in the entire fraction range of inclusion. It is demonstrated for porous samples that the proposed method can reproduce power-law behavior with regard to porosity.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Strain analysis in ultrathin silicide layers in Fe∕CsCl–57FeSi∕Fe sandwiches

B. Croonenborghs, F. M. Almeida, S. Cottenier, M. Rots, A. Vantomme, and J. Meersschaut

Appl. Phys. Lett. 85, 200 (2004); http://dx.doi.org/10.1063/1.1768307 (3 pages) | Cited 8 times

Online Publication Date: 8 July 2004

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Epitaxially stabilized iron monosilicide films with the CsCl structure (B2-FeSi) have been investigated by conversion electron Mössbauer spectroscopy and x-ray diffraction. A detailed investigation of the elastic strain in these metastable layers is presented. Using hyperfine interaction information the tetragonal distortion of the silicide lattice could be quantified for layers as thin as 14 math. A general tendency for strain relaxation with increasing layer thickness is observed.
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76.80.+y Mössbauer effect; other γ-ray spectroscopy
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
71.70.Jp Nuclear states and interactions
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.35.Gy Mechanical properties; surface strains

Physical origin of trench formation in Ge∕Si(100) islands

Ph. Sonnet and P. C. Kelires

Appl. Phys. Lett. 85, 203 (2004); http://dx.doi.org/10.1063/1.1771452 (3 pages) | Cited 17 times

Online Publication Date: 8 July 2004

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Monte Carlo simulations of stress buildup and relief shed light onto the physical origin of trench formation in Ge∕Si(100) islands. By monitoring the stress evolution as the island grows layer by layer, we find that a trench is most likely being formed halfway during growth. The primary driving force for this phenomenon is the reduction of the concentrated stress below the edges of the island, but not the need to provide Si into it, as is widely believed. However, once the trench is formed, subsequent intermixing through it is enhanced, and nearly compensates for the stress in the island.
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68.60.-p Physical properties of thin films, nonelectronic

Photoluminescence of AlGaN grown on bulk AlN substrates

G. Tamulaitis, I. Yilmaz, M. S. Shur, Q. Fareed, R. Gaska, and M. A. Khan

Appl. Phys. Lett. 85, 206 (2004); http://dx.doi.org/10.1063/1.1771804 (3 pages) | Cited 10 times

Online Publication Date: 8 July 2004

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The photoluminescence (PL) of AlGaN quantum wells with AlN barrier layers deposited on substrates fabricated of AlN single crystals is studied in the temperature range from 11 to 300 K under pulsed band-to-band excitation of the well material. The abnormal temperature dependence of the PL peak position and differences in the character of the peak shift with increasing excitation power density observed at low and elevated temperatures are interpreted in terms of carrier/exciton localization and screening of the built-in electric field. The formation of these localized states with narrow energy distribution and high density is favorable for efficient light emission.
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81.07.St Quantum wells
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.65.Fg Quantum wells
78.67.De Quantum wells
73.20.Fz Weak or Anderson localization

Effect of H+ on Fe–Mg interdiffusion in olivine, (Fe,Mg)2SiO4

Zhongyan Wang, Takehiko Hiraga, and D. L. Kohlstedt

Appl. Phys. Lett. 85, 209 (2004); http://dx.doi.org/10.1063/1.1769593 (3 pages) | Cited 13 times

Online Publication Date: 8 July 2004

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To quantify the effect of hydrogen on the kinetics of Fe–Mg interdiffusion in olivine, diffusion couples composed of crystals with Mg∕(Mg+Fe) ratios of 0.91 and 0.83 were annealed under water-saturated conditions at T=1373 K and P=300 MPa. With fO2 buffered at the Ni–NiO phase boundary, fH2O≈300 MPa. The resulting interdiffusivity, mathFe–Mg≈1×10−16 m2∕s, is approximately one order of magnitude larger than that measured under anhydrous conditions. The enhancement in diffusivity in the presence of water results from an increase in the concentration of cation vacancies associated with the introduction of high concentrations of protons as point defects into the olivine structure.
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66.30.Ny Chemical interdiffusion; diffusion barriers
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.72.J- Point defects and defect clusters

Real-time evolution of the indium tin oxide film properties and structure during annealing in vacuum

A. Rogozin, N. Shevchenko, M. Vinnichenko, F. Prokert, V. Cantelli, A. Kolitsch, and W. Möller

Appl. Phys. Lett. 85, 212 (2004); http://dx.doi.org/10.1063/1.1771456 (3 pages) | Cited 11 times

Online Publication Date: 8 July 2004

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Indium tin oxide films produced by reactive middle frequency magnetron sputtering were annealed in a vacuum. The electrical and optical properties of the film have been studied in situ along with direct characterization of the crystalline structure. Even in the amorphous state, the film resistivity significantly decreases with increasing temperature due to a free-electron density enhancement, likely by the generation of oxygen vacancies. A rapid crystallization within the temperature range of 250–280 °C leads to a further decrease of the resistivity due to Sn donor activation. The resistivity and the optical properties depend nonlinearly on the crystalline fraction.
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81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
81.15.Cd Deposition by sputtering
61.66.Fn Inorganic compounds
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
64.70.K- Solid-solid transitions

Initial growth of interfacial oxide during deposition of HfO2 on silicon

K. Choi, H. Temkin, H. Harris, S. Gangopadhyay, L. Xie, and M. White

Appl. Phys. Lett. 85, 215 (2004); http://dx.doi.org/10.1063/1.1771457 (3 pages) | Cited 8 times

Online Publication Date: 8 July 2004

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Interfacial chemistry of Hf∕Si, HfO2∕SiO2∕Si, and HfO2∕Si is investigated by x-ray photoelectron spectroscopy in order to understand the interfacial layer formation mechanism. Deposition of Hf and HfO2 films was carried out on Si wafers by electron-beam evaporation with oxygen backfill. We show that the interfacial layer formation takes place predominantly at the initial stage of the HfO2 film deposition. Temporary direct bonding between Hf metal and Si is proposed to be the source of the catalytic reaction resuting in formation of interfacial layer. Formation of interfacial layer was suppressed by chemically grown thin oxide blocking the direct Si–Hf bonding. We also demonstrate reduced interfacial layer after modified Shiraki surface etch, compared to the Radio Corporation of America clean. This indicates that a more complete hydrogen termination and atomically smoother surface can delay the onset of interfacial layer formation.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Jv Interfaces; heterostructures; nanostructures
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.65.Cf Surface cleaning, etching, patterning

Effects of chemical composition on the optical properties of Zn1−xCdxO thin films

Sang Yeol Lee, Y. Li, Jang-Sik Lee, J. K. Lee, M. Nastasi, S. A. Crooker, Q. X. Jia, Hong-Seong Kang, and Jeong-Seok Kang

Appl. Phys. Lett. 85, 218 (2004); http://dx.doi.org/10.1063/1.1771810 (3 pages) | Cited 25 times

Online Publication Date: 8 July 2004

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Zn1−xCdxO thin films were deposited on (0001) sapphire substrates by pulsed-laser deposition. Structural and optical properties of Zn1−xCdxO films were strongly correlated to the processing conditions. The composition of the films varied nonmonotonically as a function of deposition temperatures due to the difference of vapor pressure between Cd and Zn species. The optical energy bandgap of Zn1−xCdxO thin films, measured by photoluminescence and transmittance, changed from 3.249 to 3.291 eV. The change of the optical properties was mainly attributed to the change of the stoichiometry of Zn1−xCdxO, as determined by Rutherford backscattering spectroscopy.
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78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Et II-VI semiconductors
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
81.15.Fg Pulsed laser ablation deposition

Correlated diffusion of silicon and boron in thermally grown SiO2

Masashi Uematsu, Hiroyuki Kageshima, Yasuo Takahashi, Shigeto Fukatsu, Kohei M. Itoh, and Kenji Shiraishi

Appl. Phys. Lett. 85, 221 (2004); http://dx.doi.org/10.1063/1.1771811 (3 pages) | Cited 8 times

Online Publication Date: 8 July 2004

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Si self-diffusion and B diffusion in SiO2 were simultaneously investigated in thermally grown 28SiO2 co-implanted with 30Si and B. The B diffusivity increases with decreasing distance between the implanted B and Si∕SiO2 interface, in the same way as Si self-diffusivity. This result together with a numerical simulation shows that SiO molecules, which are generated at the Si∕SiO2 interface and diffusing into SiO2, enhance not only Si self-diffusion, but also B diffusion. In addition, we found that the diffusivities of both Si and B increase with higher B concentration in SiO2. The experimental results can be quantitatively explained by a numerical simulation assuming that the diffusivity of SiO, which enhances the diffusivities of Si and B, increases with higher B concentration.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
61.72.S- Impurities in crystals
66.30.J- Diffusion of impurities

Highly sensitive photoalignment of liquid crystals through polarization preserved triplet energy transfer

Seiichi Furumi and Kunihiro Ichimura

Appl. Phys. Lett. 85, 224 (2004); http://dx.doi.org/10.1063/1.1771813 (3 pages) | Cited 4 times

Online Publication Date: 8 July 2004

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Highly sensitive photoalignment of liquid crystals (LCs) can be realized by the polarization preserved triplet energy transfer from doped sensitizers to cinnamate side chains of a photocrosslinkable polymer. Linearly polarized irradiation of sensitizer-doped polymer films with 365 nm light for selective excitation of the triplet photosensitizer gives rise to azimuthal photodichroism of cinnamates as a result of nanometric triplet energy transfer process preserving the polarization state of triplet-excited photosensitizer. This phenomenon is applicable to the surface-assisted orientational photocontrol of nematic LCs with high performance of extremely low exposure energies.
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78.66.Qn Polymers; organic compounds
61.30.Vx Polymer liquid crystals
78.55.Kz Solid organic materials
71.35.-y Excitons and related phenomena

Concentration quenching of Eu-related luminescence in Eu-doped GaN

Hyungjin Bang, Shinichi Morishima, Junji Sawahata, Jongwon Seo, Mikio Takiguchi, Masato Tsunemi, Katsuhiro Akimoto, and Masaharu Nomura

Appl. Phys. Lett. 85, 227 (2004); http://dx.doi.org/10.1063/1.1771806 (3 pages) | Cited 28 times

Online Publication Date: 8 July 2004

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The dependence of Europium (Eu)-related luminescence intensity on the Eu concentration in Eu-doped GaN was studied. This luminescence is observed at 622 nm and originates from the intra-4f transition of the Eu3+ ion. The intensity of the luminescence increased with increasing Eu concentration, up to about 2 at. %, and then abruptly decreased. It was found that polycrystalline growth began to be induced at Eu concentrations of more than 2 at. %. In addition, clear evidence for the formation of EuN compounds was obtained by x-ray diffraction and extended x-ray absorption fine structure analysis. The cause of the concentration quenching is likely to be related to the polycrystalline growth as well as EuN formation.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
61.72.S- Impurities in crystals
78.70.Dm X-ray absorption spectra

Microrubbing technique to produce high pretilt multidomain liquid crystal alignment

Soney Varghese, Gregory P. Crawford, Cees W. M. Bastiaansen, Dick K. G. de Boer, and Dirk J. Broer

Appl. Phys. Lett. 85, 230 (2004); http://dx.doi.org/10.1063/1.1773375 (3 pages) | Cited 21 times

Online Publication Date: 8 July 2004

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We disclose a microrubbing (μ-rubbing) technique to create multidomain alignment in liquid crystal displays. A small metallic sphere under sufficient load is used to directly rub a polyimide alignment layer that is known to enforce homeotropic boundary conditions of the liquid crystal. We demonstrate a 47 μm linewidth and a 10° pretilt with respect to the substrate plane. We report on the electro-optic performance properties and viewing angle characteristics of four domain samples, where the midplane angle of the director is oriented in four different directions.
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85.60.Pg Display systems

V-shaped inversion domains in InN grown on c-plane sapphire

J. Jasinski, Z. Liliental-Weber, H. Lu, and W. J. Schaff

Appl. Phys. Lett. 85, 233 (2004); http://dx.doi.org/10.1063/1.1772863 (3 pages) | Cited 10 times

Online Publication Date: 8 July 2004

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Inversion domains with a V shape were found to nucleate inside a Mg-doped InN heteroepitaxial layer. They resemble Al-polarity domains, observed recently, in N-polarity AlN films. However, the angle between the sidewalls of the V-shaped domain and the c axis differs in these two cases. In InN, this angle is almost two times bigger than that reported for AlN. The origin of V-shaped inversion domains in InN film is not yet clear.
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61.72.uj III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
81.05.Ea III-V semiconductors
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