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6 Mar 2006

Volume 88, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 103107 (2006); http://dx.doi.org/10.1063/1.2182096 (3 pages)

A. B. Djurišić, Y. H. Leung, K. H. Tam, L. Ding, W. K. Ge, H. Y. Chen, and S. Gwo
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Observation of difference-frequency generation by mixing of terahertz and near-infrared laser beams in a GaSe crystal

Wei Shi, Yujie J. Ding, Nils Fernelius, and F. Ken Hopkins

Appl. Phys. Lett. 88, 101101 (2006); http://dx.doi.org/10.1063/1.2177363 (3 pages) | Cited 9 times

Online Publication Date: 6 March 2006

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We have observed difference-frequency generation by mixing terahertz and near-infrared laser beams in a GaSe crystal (i.e., terahertz frequency upconversion). This process has a potential for detecting terahertz waves. Using an InGaAs photodiode operating at room temperature the minimum detectable energy per pulse was 9.75 nJ. When a fast photomultiplier tube was used instead, the lowest-energy per pulse was measured to be 245 pJ. In addition, the temporal profile of the terahertz pulses was measured with a ns resolution.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Low-switching-energy and high-repetition-frequency all-optical flip-flop operations of a polarization bistable vertical-cavity surface-emitting laser

Takashi Mori, Yasuhiro Yamayoshi, and Hitoshi Kawaguchi

Appl. Phys. Lett. 88, 101102 (2006); http://dx.doi.org/10.1063/1.2181192 (3 pages) | Cited 33 times

Online Publication Date: 6 March 2006

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Subfemtojoule polarization bistable switching in a vertical-cavity surface-emitting laser (VCSEL) is experimentally demonstrated. All-optical flip-flop operation of the VCSEL was performed using two orthogonally polarized injection light pulses. The optimum wavelengths of the two injection pulses for achieving minimum switching power were different and corresponded to the lasing wavelengths of the two polarization states of the laser. The pulse width/switching frequency dependence of the injection pulses showed that a minimum switching energy was obtained at 1 ns/500 MHz. A record low switching energy of 0.3 fJ has been achieved as well as a record high switching frequency of 10 GHz.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Pc Optical bistability, multistability, and switching, including local field effects

In situ monitoring of GaN epitaxial lateral overgrowth by spectroscopic reflectometry

C. Liu, S. Stepanov, P. A. Shields, A. Gott, W. N. Wang, E. Steimetz, and J.-T. Zettler

Appl. Phys. Lett. 88, 101103 (2006); http://dx.doi.org/10.1063/1.2182013 (3 pages) | Cited 1 time

Online Publication Date: 6 March 2006

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The application of spectroscopic reflectometry to the monitoring of epitaxial lateral overgrowth of GaN in low pressure metalorganic vapor phase epitaxy has been investigated. Real-time vertical and lateral growth rates and hence thickness and wing width of the growing GaN are extracted. A vertical growth enhancement was clearly observed at an early stage, followed by vertical growth suppression until full coalescence was achieved. The lateral to vertical growth ratio was obtained showing clear time dependent characteristics. The observations were explained by considering the mass transport between the growing (0001) facets and the {11math0} sidewall facets.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.A- Nucleation and growth
78.66.Fd III-V semiconductors

Highly efficient white-light-emitting diodes fabricated with short-wavelength yellow oxynitride phosphors

Rong-Jun Xie, Naoto Hirosaki, Mamoru Mitomo, Kosei Takahashi, and Ken Sakuma

Appl. Phys. Lett. 88, 101104 (2006); http://dx.doi.org/10.1063/1.2182067 (3 pages) | Cited 87 times

Online Publication Date: 6 March 2006

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We have already reported orangish yellow Ca–α-SiAlON:Eu2+ phosphors, and applied them to fabricate warm white light-emitting diodes (LEDs). In this letter, we report on greenish yellow Li–α-SiAlON:Eu2+ phosphors, and use them to create daylight when coupled to an InGaN blue LED chip (460 nm). The newly discovered Li–α-SiAlON:Eu2+ phosphors emit at shorter wavelengths of 573–577 nm under the 460 nm excitation, and exhibit a smaller Stokes shift than Ca–α-SiAlON:Eu2+ does. By using this short-wavelength yellow oxynitride phosphor, bright daylight emissions from white LEDs can be generated. Thus, highly efficient white LEDs with tunable white light can be fabricated with α-SiAlON:Eu2+ phosphors, enabling them for a wider range of applications.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence

Lasing in an intermediate twisted phase between cholesteric and smectic A phase

Andro Chanishvili, Guram Chilaya, Gia Petriashvili, Riccardo Barberi, Maria P. De Santo, Mario A. Matranga, and Federica Ciuchi

Appl. Phys. Lett. 88, 101105 (2006); http://dx.doi.org/10.1063/1.2183822 (3 pages) | Cited 7 times

Online Publication Date: 7 March 2006

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This work describes the observation of lasing in an intermediate chiral phase of a dye-doped cholesteric liquid crystal mixture. This intermediate phase exists between cholesteric and smectic A phase and it presents anomalous selective reflection properties. The lasing was observed at the long-wavelength edge of the photonic band gap.
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42.55.-f Lasers
42.70.Hj Laser materials
42.70.Df Liquid crystals
61.30.-v Liquid crystals
42.70.Qs Photonic bandgap materials

Nonlinear dynamics accompanying polarization switching in vertical-cavity surface-emitting lasers with orthogonal optical injection

I. Gatare, M. Sciamanna, J. Buesa, H. Thienpont, and K. Panajotov

Appl. Phys. Lett. 88, 101106 (2006); http://dx.doi.org/10.1063/1.2181649 (3 pages) | Cited 25 times

Online Publication Date: 8 March 2006

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We present an experimental investigation of a vertical-cavity surface-emitting laser (VCSEL) submitted to orthogonal optical injection, i.e., the injected light is linearly polarized and orthogonal to that emitted by the solitary VCSEL. Bifurcation boundaries of qualitatively different dynamics are mapped out in the frequency detuning-injection strength plane. We unveil rich and complex dynamics including injection locking, limit cycle, wave mixing, and period doubling route to chaos.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics

Liquid-crystal-based terahertz tunable Lyot filter

Chao-Yuan Chen, Ci-Ling Pan, Cho-Fan Hsieh, Yea-Feng Lin, and Ru-Pin Pan

Appl. Phys. Lett. 88, 101107 (2006); http://dx.doi.org/10.1063/1.2181271 (3 pages) | Cited 30 times

Online Publication Date: 8 March 2006

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A two-element tunable Lyot filter operating in the terahertz (THz) frequency range is demonstrated. The central bandpass frequency of the filter can be continuously tuned from 0.388 to 0.564 THz (a fractional tuning range of 40%) using magnetically controlled birefringence in nematic liquid crystals. The transmission bandwidth is 0.1 THz and the insertion loss of the present device is 8 dB due to the scattering of LC molecules in the thick LC cells. This filter can be operated at room temperature.
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42.79.Kr Display devices, liquid-crystal devices
84.40.-x Radiowave and microwave (including millimeter wave) technology
42.79.Ci Filters, zone plates, and polarizers

Negative feedback optical amplification effect based on cross-gain modulation in semiconductor optical amplifiers

Yoshinobu Maeda

Appl. Phys. Lett. 88, 101108 (2006); http://dx.doi.org/10.1063/1.2183748 (3 pages) | Cited 2 times

Online Publication Date: 8 March 2006

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A negative feedback optical amplification effect was confirmed using negative feedback based on cross-gain modulation in an InGaAsP/InP semiconductor optical amplifier. The optical amplifier with negative feedback was capable of providing an output signal whose gain, wave form and baseline, were stabilized optically. The distortion of the wave form was extremely small in a wide frequency band of 0.1–10 GHz. In addition, the gain can be adjusted by controlling the amount of negative feedback power using a variable optical attenuator. In physics, the optical amplifier is considered as the optical equivalent of a noninverting operational amplifier in electronics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Fabricating subwavelength array structures using a near-field photolithographic method

Wei-Lun Chang, Yu-Jen Chang, Pei-Kuen Wei, and Pei Hsi Tsao

Appl. Phys. Lett. 88, 101109 (2006); http://dx.doi.org/10.1063/1.2185249 (3 pages) | Cited 1 time

Online Publication Date: 9 March 2006

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This work presents a photolithographic approach for producing high aspect ratio arrays in photoresist. The photomask is composed of hexagonal/square rod arrays with a thickness of 0.2 μm and a period of 600 nm. Illuminating the photomask with a blue laser generates periodically focused beams up to 1 μm long and less than 300 nm wide. A hexagonal rod array provides a better focused beam than a square array due to its higher symmetry. Finite-difference time-domain calculations elucidate the existence of long focused beams above the photomask. Optical near-field measurements verified those subwavelength beams originating from the rod regions.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays
02.70.Bf Finite-difference methods

Mode locking of lateral modes in broad-area semiconductor lasers by subharmonic optical pulse injection

Joachim Kaiser, Ingo Fischer, and Wolfgang Elsässer

Appl. Phys. Lett. 88, 101110 (2006); http://dx.doi.org/10.1063/1.2185252 (3 pages)

Online Publication Date: 9 March 2006

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We generate stable mode-locking of different lateral modes in broad-area semiconductor lasers (BALs) by local injection of short optical pulses repeated at subharmonics of the lateral mode separation. The locking results in a persistent, periodic spatiotemporal dynamics consisting of a laterally alternating intensity modulation with a repetition rate of 3.4 GHz, which can be regarded as an enhancement and stabilization of the spontaneous dynamic filamentation that is frequently observed in free running BALs.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics

Ge on Si p-i-n photodiodes operating at 10 Gbit/s

Lorenzo Colace, Michele Balbi, Gianlorenzo Masini, Gaetano Assanto, Hsin-Chiao Luan, and Lionel C. Kimerling

Appl. Phys. Lett. 88, 101111 (2006); http://dx.doi.org/10.1063/1.2182110 (3 pages) | Cited 32 times

Online Publication Date: 9 March 2006

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We report on fast p-i-n photodetectors operating in the near infrared and realized in pure germanium on silicon. The diodes were fabricated by chemical vapor deposition at 600 °C without affecting the crystal quality and allowing the integration with standard silicon processes. We demonstrate responsivities of 0.4 and 0.2 A/W at 1.3 and 1.55 μm, respectively, as well as operation at 10 Gbit/s.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Systematic study of the size and spacing dependence of Ag nanoparticle enhanced fluorescence using electron-beam lithography

T. D. Corrigan, S.-H. Guo, H. Szmacinski, and R. J. Phaneuf

Appl. Phys. Lett. 88, 101112 (2006); http://dx.doi.org/10.1063/1.2176862 (3 pages) | Cited 12 times

Online Publication Date: 10 March 2006

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We study the enhancement of fluorescence by Ag nanopillars on a semiconducting substrate in which the pillar size, shape, and spacing is varied systematically using electron-beam lithography. Local maxima in the enhancement versus lateral size, as large as a factor of ∼ 20 are observed, and vary both with the shape of the pillars and the wavelength of the excitation. We find that the size, shape, and spacing dependence is in qualitative agreement with a model based upon resonant coupling with particle plasmon polaritons. We also find increased enhancement for particle shapes producing high local electric fields.
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78.55.Hx Other solid inorganic materials
61.46.-w Structure of nanoscale materials
81.16.Nd Micro- and nanolithography
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Corner-pumped Yb: yttrium aluminum garnet slab laser emitted up to 1 kW

Qiang Liu, Mali Gong, Fuyuan Lu, Wupeng Gong, Chen Li, and Dongdong Ma

Appl. Phys. Lett. 88, 101113 (2006); http://dx.doi.org/10.1063/1.2186740 (3 pages) | Cited 12 times

Online Publication Date: 10 March 2006

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We have developed a slab laser design based on conduction cooling and a novel pumping geometry called corner pumping. The design uses a slab crystal configuration with the pump light incident from the slab corners. A maximum output power of over 1 kW was achieved from a 1 mm thick Yb:YAG/YAG (YAG = yttrium aluminum garnet) structure with a 0.5 at. %-doped Yb:YAG. The slope efficiency and optical-to-optical efficiency with respect to the total pump power were 42.8% and 33.6%, respectively. At this pump power the electrical-to-optical conversion efficiency of the system was 16.8%.
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42.60.By Design of specific laser systems
42.55.Rz Doped-insulator lasers and other solid state lasers

Translational velocity measurement for single floating cell based on optical Fourier transform theory

Katsumi Ishizaki, Ichirou Ishimaru, Makoto Yoshida, Yusuke Inoue, Toshiki Yasokawa, Shigeki Kuriyama, Tsutomu Masaki, Seiji Nakai, Kaoru Takegawa, and Naotaka Tanaka

Appl. Phys. Lett. 88, 101114 (2006); http://dx.doi.org/10.1063/1.2183747 (2 pages) | Cited 7 times

Online Publication Date: 10 March 2006

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This letter reports on translational velocity measurement, which is needed for tracking a low contrast cell. We propose a new optical spatial filtering method that is based on the optical Fourier transform theory. In this method, a pinhole is installed as a spatial filter on the optical Fourier transform plane. By means of this spatial filter, the arbitrary component of the spatial frequency is derived from the random refractive index distribution as the periodic light intensity distribution. By observing the changes of this light intensity, we can obtain the translational velocity of a low-contrast cell by means of a high-response photodiode.
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87.80.-y Biophysical techniques (research methods)
87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics
87.17.Jj Cell locomotion, chemotaxis
42.30.Kq Fourier optics
42.79.Ci Filters, zone plates, and polarizers
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Effect of radio-frequency power levels on electron density in a confined two-frequency capacitively-coupled plasma processing tool

S. K. Karkari and A. R. Ellingboe

Appl. Phys. Lett. 88, 101501 (2006); http://dx.doi.org/10.1063/1.2182073 (3 pages) | Cited 33 times

Online Publication Date: 6 March 2006

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The plasma electron density ne in a symmetric confined capacitive-coupled plasma processing tool containing Ar/O2/C4F8 gas mixtures is studied as a function of two, combined radio frequency (2 MHz+27 MHz) powers. For measuring ne we have used a floating hairpin resonance probe. The results show a linear increase in ne with 27 MHz power. Also the density is higher with an increase in 2 MHz power, in contrast with published particle-in-cell simulation results in argon where the plasma density decreased with increases in low frequency voltage, for fixed high frequency current [ P. C. Boyle et al., J. Phys. D 37, 697 (2004) ]. Analyzing the relative phase between radio frequency current and voltage, we observe slightly lower 2 MHz phase shifts at higher 2 MHz voltage, which is attributed to an increase in the real component of the current through the sheath. This is possible due to the increase in secondary electron emissions arising from ion bombardment, which is favored by an increase in 2 MHz voltage. We therefore conclude that the secondary electrons could play an important role in the discharge process.
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52.50.Dg Plasma sources
52.25.Tx Emission, absorption, and scattering of particles
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.40.Kh Plasma sheaths
52.80.Pi High-frequency and RF discharges

Current filamentation in discharge-excited F2-based excimer laser gas mixtures

D. Mathew, H. M. J. Bastiaens, K.-J. Boller, and P. J. M. Peters

Appl. Phys. Lett. 88, 101502 (2006); http://dx.doi.org/10.1063/1.2183363 (3 pages) | Cited 3 times

Online Publication Date: 8 March 2006

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Discharge instabilities in x-ray preionized F2-doped excimer laser gas mixtures are investigated using an intensified charge coupled device camera with a gating time of 300 ps. In contradiction with earlier theories and observations, it is found that the discharges in He/F2 mixtures are homogeneous only at very low concentration of F2 (0.025%). We present experimental results, which prove that in He/Kr/F2 mixtures the appearance of discharge filaments is coupled with the presence of F2 rather than Kr.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.80.Hc Glow; corona
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems

Anisotropic plasma effects on electron capture process in an anisotropic plasma

Dong-Soo Shin and Young-Dae Jung

Appl. Phys. Lett. 88, 101503 (2006); http://dx.doi.org/10.1063/1.2185253 (3 pages)

Online Publication Date: 9 March 2006

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The anisotropic and plasma screening effects on the electron capture process are investigated in an anisotropic plasma in the presence of an external electric field. The Bohr–Lindhard model with the impact parameter analysis is applied to obtain the electron capture probability in the anisotropic plasma as a function of the impact parameter, Debye length, and collision energy. The result shows that the electron capture cross section decreases with increasing collision energy. It is also found that the anisotropic effect strongly suppresses the electron capture cross section in the anisotropic plasma.
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52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Silicon and silicon oxide etching rate enhancement by nitrogen containing gas addition in remote perfluorocarbon plasmas

Bo Bai, Jujin An, and Herbert H. Sawin

Appl. Phys. Lett. 88, 101504 (2006); http://dx.doi.org/10.1063/1.2185254 (3 pages) | Cited 4 times

Online Publication Date: 9 March 2006

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The addition of 3% nitrogen to a mixture of perfluorocarbon/oxygen/argon in a remote toroidal plasma source was shown to double the etching rate of both silicon dioxide and silicon in a downstream process. It is believed that the nitrogen blocks the surface recombination sites for COF2 formation on the wall of the transfer tube, thereby transporting more fluorine atoms to the downstream process chamber and increasing the etching rate.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
52.50.Dg Plasma sources
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Fi Transport properties
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Transparent indium zinc oxide ohmic contact to phosphor-doped n-type zinc oxide

Guangxia Hu, Bhupendra Kumar, Hao Gong, E. F. Chor, and Ping Wu

Appl. Phys. Lett. 88, 101901 (2006); http://dx.doi.org/10.1063/1.2178404 (3 pages) | Cited 23 times

Online Publication Date: 6 March 2006

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Transparent indium zinc oxide (IZO) ohmic contacts to phosphor-doped n-type ZnO have been formed. The resistance, transmittance, and phase reliability of the contacts were investigated. As deposited, an ohmic contact was formed with a specific contact resistance of about 1.1×10−4 Ω cm2 and the transmittance of the ZnO/IZO (520/350 nm) film was more than 75% in the 450–1100 nm wavelength range. After annealing at 400 °C for 5 min in a vacuum (2×10−5 mbar), the specific contact resistance was reduced by about two orders of magnitude to 3.8×10−6 Ω cm2, while maintaining the contact stability and high optical transparency.
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81.05.Dz II-VI semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Cg Contact resistance, contact potential
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

Synthesis and temperature-dependent near-band-edge emission of chain-like Mg-doped ZnO nanoparticles

W. Q. Peng, S. C. Qu, G. W. Cong, and Z. G. Wang

Appl. Phys. Lett. 88, 101902 (2006); http://dx.doi.org/10.1063/1.2182010 (3 pages) | Cited 13 times

Online Publication Date: 6 March 2006

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Chain-like Mg-doped ZnO nanoparticles were prepared using a wet chemical method combined with subsequent heat treatment. The blueshifted near-band-edge emission of the doped ZnO sample with respect to the undoped one was investigated by temperature-dependent photoluminescence. Based on the energy shift of the free-exciton transition, a band gap enlargement of ∼ 83 meV was estimated, which seems to result in the equivalent shift of the bound-exciton transition. At 50 K, the transformation from the donor-acceptor-pair to free-to-acceptor emissions was observed for both the undoped and doped samples. The results show that Mg doping leads to the decrease of the acceptor binding energy.
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78.55.Et II-VI semiconductors
71.20.Nr Semiconductor compounds
61.72.uj III-V and II-VI semiconductors
71.35.-y Excitons and related phenomena
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

White-light generation and energy transfer in SrZn2(PO4)2:Eu,Mn phosphor for ultraviolet light-emitting diodes

Woan-Jen Yang and Teng-Ming Chen

Appl. Phys. Lett. 88, 101903 (2006); http://dx.doi.org/10.1063/1.2182026 (3 pages) | Cited 80 times

Online Publication Date: 6 March 2006

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The SrZn2(PO4)2:Eu2+,Mn2+ phosphor shows two emission bands under ultraviolet radiation; the one observed at 416 nm is attributed to Eu2+ occupying the Sr2+ sites and the other asymmetric band deconvoluted into two peaks was found to center at 538 and 613 nm, which originate from Mn2+ occupying two different Zn2+ sites. The energy transfer from Eu2+ to Mn2+ has been demonstrated to be a resonant type via a dipole-quadrupole mechanism. By utilizing the principle of energy transfer and appropriate tuning of activator contents, we have demonstrated that SrZn2(PO4)2:Eu2+,Mn2+ is potentially useful as an ultraviolet-convertible phosphor for white-light emitting diodes.
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78.55.Hx Other solid inorganic materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Effect of nitrogen ion bombardment on defect formation and luminescence efficiency of GaNP epilayers grown by molecular-beam epitaxy

D. Dagnelund, I. A. Buyanova, T. Mchedlidze, W. M. Chen, A. Utsumi, Y. Furukawa, A Wakahara, and H. Yonezu

Appl. Phys. Lett. 88, 101904 (2006); http://dx.doi.org/10.1063/1.2182028 (3 pages) | Cited 5 times

Online Publication Date: 6 March 2006

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Radiative efficiency of GaNP epilayers grown on GaP substrates by solid-source molecular beam epitaxy is significantly improved by reduced nitrogen ion bombardment during the growth. Based on the results of temperature-dependent photoluminescence (PL) and optically detected magnetic resonance studies (ODMR), the observed improvements are attributed to reduced formation of defects, such as a Ga interstitial related defect and an unidentified defect revealed by ODMR. We demonstrate that these defects act as competing recombination centers, which promote thermal quenching of the PL intensity and result in a substantial (34×) decrease in room-temperature PL intensity.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.J- Point defects and defect clusters
76.70.Hb Optically detected magnetic resonance (ODMR)

Raman study of lattice dynamic behaviors in phosphorus-doped ZnO films

J. D. Ye, S. L. Gu, S. M. Zhu, S. M. Liu, Y. D. Zheng, R. Zhang, Y. Shi, Q. Chen, H. Q. Yu, and Y. D. Ye

Appl. Phys. Lett. 88, 101905 (2006); http://dx.doi.org/10.1063/1.2182107 (3 pages) | Cited 26 times

Online Publication Date: 6 March 2006

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Phosphorus-induced lattice dynamic behaviors in ZnO:P epilayers grown by the metalorganic chemical vapor deposition technique have been studied using the Raman scattering method. Additional modes around 504, 520, 655, and 866 cm−1 are attributed to the disorder-activated modes due to the breakdown of translational symmetry by P doping, well supported by the reported ab initio calculations of lattice dynamics in w-ZnO. Two modes around 364 and 478 cm−1 are assigned to the local vibrational modes of Zn–P and P–O pairs, respectively. The correlation of transport and vibrational properties demonstrates the complex doping mechanism and the amphoteric nature of P dopant in ZnO. In addition, the redshift of 2 longitudinal optical multiphonon around 1154 cm−1 is possibly originated from the variation of short-range forces in ZnO uniaxial lattice caused by P incorporation.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.66.Hf II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Predicting hardness of dense C3N4 polymorphs

Julong He, Licong Guo, Xiaoju Guo, Riping Liu, Yongjun Tian, Huitian Wang, and Chunxiao Gao

Appl. Phys. Lett. 88, 101906 (2006); http://dx.doi.org/10.1063/1.2182109 (3 pages) | Cited 23 times

Online Publication Date: 6 March 2006

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We report the calculations of the Vickers hardness of five predicted C3N4 polymorphs by using the microscopic model of hardness. The hardest phase, cubic C3N4, has the hardness of 92.0 GPa, softer than diamond, although its modulus is higher than that of diamond. The densest phase, cubic spinel C3N4, has the lowest hardness of 62.3 GPa in the five polymorphs. Our analysis suggests that the hardness of simple-structured covalent materials might not exceed that of diamond.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
61.66.Fn Inorganic compounds

Ternary bulk metallic glasses formed by minor alloying of Cu8Zr5 icosahedron

Junhai Xia, Jianbing Qiang, Yingmin Wang, Qing Wang, and Chuang Dong

Appl. Phys. Lett. 88, 101907 (2006); http://dx.doi.org/10.1063/1.2183367 (3 pages) | Cited 24 times

Online Publication Date: 7 March 2006

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Icosahedron Cu8Zr5, derived from the Cu8Zr3 phase structure, corresponds to the deepest eutectic Cu0.618Zr0.382. Near this composition is the best glass-forming Cu–Zr composition, Cu0.64Zr0.36. (Cu0.64Zr0.36)1−xMx and (Cu0.618Zr0.382)1−xMx were examined for glass formation, where M represents Nb, Sn, Mo, Si, V, Ag, or Ta. A series of Cu–Zr based bulk metallic glasses are discovered with minor Nb, Sn, Mo, Ag, and Ta additions (lower than 3 at. %). The minor alloying mechanism was discussed in the light of atomic size and electron concentration factors.
Show PACS
81.05.Kf Glasses (including metallic glasses)
61.43.Fs Glasses
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