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17 May 2010

Volume 96, Issue 20, Articles (20xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 203102 (2010); http://dx.doi.org/10.1063/1.3429125 (3 pages)

Qimin Quan, Parag B. Deotare, and Marko Loncar
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Optical transmission of periodic annular apertures in metal film on high-refractive index substrate: The role of the nanopillar shape

J.-S. Bouillard, J. Einsle, W. Dickson, S. G. Rodrigo, S. Carretero-Palacios, L. Martin-Moreno, F. J. Garcia-Vidal, and A. V. Zayats

Appl. Phys. Lett. 96, 201101 (2010); http://dx.doi.org/10.1063/1.3427390 (3 pages) | Cited 1 time

Online Publication Date: 17 May 2010

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The influence of annular aperture parameters on the optical transmission through arrays of coaxial apertures in a metal film on high refractive index substrates has been investigated experimentally and numerically. It is shown that the transmission resonances are related to plasmonic crystal effects rather than frequency cutoff behavior associated with annular apertures. The role of deviations from ideal aperture shape occurring during the fabrication process has also been studied. Annular aperture arrays are often considered in many applications for achieving high optical transmission through metal films and understanding of nanofabrication tolerances are important.
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78.66.Bz Metals and metallic alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.07.Bc Nanocrystalline materials
75.75.-c Magnetic properties of nanostructures

Improved electroluminescence from n-ZnO/AlN/p-GaN heterojunction light-emitting diodes

J. B. You, X. W. Zhang, S. G. Zhang, J. X. Wang, Z. G. Yin, H. R. Tan, W. J. Zhang, P. K. Chu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow

Appl. Phys. Lett. 96, 201102 (2010); http://dx.doi.org/10.1063/1.3430039 (3 pages) | Cited 9 times

Online Publication Date: 17 May 2010

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n-ZnO/p-GaN heterojunction light-emitting diodes with and without a sandwiched AlN layer were fabricated. The electroluminescence (EL) spectrum acquired from the n-ZnO/p-GaN displays broad emission at 650 nm originating from ZnO and weak emission at 440 nm from GaN, whereas the n-ZnO/AlN/p-GaN exhibits strong violet emission at 405 nm from ZnO without GaN emission. The EL intensity is greatly enhanced by inserting a thin AlN intermediate layer and it can be attributed to the suppressed formation of the GaOx interfacial layer and confinement effect rendered by the AlN potential barrier layer.
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85.60.Jb Light-emitting devices
78.66.Hf II-VI semiconductors
78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

On-demand entanglement source with polarization-dependent frequency shift

Xiang-Bin Wang, Cheng-Xi Yang, and Yan-Bing Liu

Appl. Phys. Lett. 96, 201103 (2010); http://dx.doi.org/10.1063/1.3427485 (3 pages) | Cited 1 time

Online Publication Date: 17 May 2010

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The polarization entanglement photon pairs generated from the biexciton cascade decay in a single semiconductor quantum dot is distorted due to the fine structure splitting. We show that, frequency of light can be shifted when it passes through an electro-optic modulator under voltage ramping. Based on this, we can realize polarization-dependent frequency shift and the hidden entanglement due to fine structure splitting can be revealed.
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73.21.La Quantum dots
78.20.Jq Electro-optical effects
71.35.-y Excitons and related phenomena
03.67.Mn Entanglement measures, witnesses, and other characterizations
03.67.Bg Entanglement production and manipulation

Terahertz surface plasmon propagation in nanoporous silicon layers

Shu-Zee A. Lo and Thomas E. Murphy

Appl. Phys. Lett. 96, 201104 (2010); http://dx.doi.org/10.1063/1.3432071 (3 pages) | Cited 1 time

Online Publication Date: 18 May 2010

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We describe the fabrication and measurement of a terahertz surface plasmon waveguide in which the optical mode is localized within a nanoporous silicon slab. We compare the propagation characteristics among waveguides with different porous layer thickness, and present an analytical model that accurately describes the dispersion and loss in the waveguides.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
63.20.Pw Localized modes
61.43.Gt Powders, porous materials

Terahertz optical sideband emission in self-assembled quantum dots

I. C. Sandall, N. E. Porter, M. Wagner, H. Schneider, S. Winnerl, M. Helm, and L. Wilson

Appl. Phys. Lett. 96, 201105 (2010); http://dx.doi.org/10.1063/1.3429681 (3 pages) | Cited 1 time

Online Publication Date: 18 May 2010

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A multilayer quantum dot sample has been excited with a strong terahertz (THz) electric field and probed with a near-infrared (NIR) laser. First- and second-order THz optical sidebands are generated on the NIR probe beam by driving quantum dot intersublevel resonances with the THz fields. A conversion efficiency of 3×10−6 was obtained for the conversion of NIR power into sideband emission at 4 K, decreasing by a factor of 20 up to room temperature. The sideband emission wavelength can be tuned over ∼ 20 nm by selection of appropriate NIR and THz frequencies, due to the inhomogeneous broadening of the dot ensemble.
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78.70.Gq Microwave and radio-frequency interactions
68.65.Ac Multilayers
81.16.Dn Self-assembly
81.07.Ta Quantum dots
78.67.Hc Quantum dots

InGaN-based light-emitting diodes grown and fabricated on nanopatterned Si substrates

Dongmei Deng, Naisen Yu, Yong Wang, Xinbo Zou, Hao-Chung Kuo, Peng Chen, and Kei May Lau

Appl. Phys. Lett. 96, 201106 (2010); http://dx.doi.org/10.1063/1.3427438 (3 pages) | Cited 1 time

Online Publication Date: 18 May 2010

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InGaN-based light-emitting diodes (LEDs) were grown and fabricated on nanoscale patterned Si (111) substrates (NPSi). Using anodized aluminum oxide as the etch mask, the NPSi was prepared with an average nanopore diameter of 150 nm and interpore distance of 120 nm. LEDs grown on NPSi exhibit relaxed tensile stress relative to the ones grown on microscale patterned Si (111) substrates (MPSi). Nanoheteroepitaxial lateral overgrowth was significantly promoted on NPSi, which led to extensive dislocation bending and annihilation. The devices made on NPSi exhibit lower leakage current and higher light output power as compared with those on MPSi.
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85.60.Jb Light-emitting devices
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.65.Cf Surface cleaning, etching, patterning
81.16.-c Methods of micro- and nanofabrication and processing

Dual rf-optical slot waveguide for ultrabroadband modulation with a subvolt Vπ

Shouyuan Shi and Dennis W. Prather

Appl. Phys. Lett. 96, 201107 (2010); http://dx.doi.org/10.1063/1.3430510 (3 pages) | Cited 2 times

Online Publication Date: 18 May 2010

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In this letter, we propose a high speed and ultralow driving voltage traveling wave electro-optic (EO) modulator based on a dual horizontal slot waveguide. The proposed design harnesses the unique properties of ferroelectric materials such as LiNBO3 and exotic, organic EO polymers to tightly confine both the optical and rf modes in a nanoscale slot maximizing the nonlinear interaction with the electric field. Larger electrode separation allows for significant reduction in rf propagation loss. Simulations of the half-wavelength voltage-length product and electro-optic response of the proposed device reveal ultrabroadband operation, up to 250 GHz, and subvolt driving voltage for a 1 cm long modulator.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Gn Optical waveguides and couplers
42.70.Jk Polymers and organics

Ultrafast all-optical magnetic switching in NaTb(WO4)2

Zuanming Jin, Hong Ma, Lihua Wang, Guohong Ma, Feiyun Guo, and Jianzhong Chen

Appl. Phys. Lett. 96, 201108 (2010); http://dx.doi.org/10.1063/1.3432072 (3 pages) | Cited 4 times

Online Publication Date: 21 May 2010

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The operation of an all-optical magnetic switching based on the paramagnetic NaTb(WO4)2 crystals is carried out by the time-resolved magneto-optical Faraday effect. Our results demonstrate that the switching time can be as fast as ∼ 500 fs at room temperature. The switching amplitude shows a linear dependence on the excitation intensity, which is proportional to the magnetization induced by the circularly polarized light. Based on the inverse Faraday effect in magneto-optical crystal, the switching mechanisms arising from circular dichroism and birefringence are discussed. By tailoring the magneto-optical properties of NaTb(WO4)2 crystal, the switching magnitude can be modulated.
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42.25.Lc Birefringence
85.70.-w Magnetic devices
33.57.+c Magneto-optical and electro-optical spectra and effects
42.25.Ja Polarization
33.55.+b Optical activity and dichroism
42.81.Gs Birefringence, polarization

Conduction and transmission analysis in gold nanolayers embedded in zinc oxide for flexible electronics

K. Sivaramakrishnan and T. L. Alford

Appl. Phys. Lett. 96, 201109 (2010); http://dx.doi.org/10.1063/1.3435467 (3 pages) | Cited 4 times

Online Publication Date: 21 May 2010

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Gold-embedded zinc oxide structures are obtained in which the conduction mechanism changes from conduction through the oxide and activated tunneling between discontinuous metal islands to metallic conduction through a near-continuous layer, with increase in gold thickness. These structures can show resistivity as low as 5.2×10−5 Ω cm. Optical transmission is elucidated in terms of gold’s absorption due to interband electronic transitions, and free carrier absorption losses combined with limitation of the mean free path in discontinuous nanoparticles. The structures show transmittance, photopic averaged transmittance, and Haacke figure of merit values of 93%, 84%, and 15.1×10−3 Ω−1, respectively.
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72.80.Ey III-V and II-VI semiconductors
73.61.Ga II-VI semiconductors
68.55.-a Thin film structure and morphology
78.66.Hf II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
77.55.-g Dielectric thin films

Temperature performance analysis of terahertz quantum cascade lasers: Vertical versus diagonal designs

Alpár Mátyás, Mikhail A. Belkin, Paolo Lugli, and Christian Jirauschek

Appl. Phys. Lett. 96, 201110 (2010); http://dx.doi.org/10.1063/1.3430741 (3 pages) | Cited 6 times

Online Publication Date: 21 May 2010

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Resonant phonon depopulation terahertz quantum cascade lasers based on vertical and diagonal lasing transitions are systematically compared using a well established ensemble Monte Carlo approach. The analysis shows that for operating temperatures below 200 K, diagonal designs may offer superior temperature performance at lasing frequencies of about 3.5 THz and above; however, vertical structures are more advantageous for good temperature performance at lower frequencies.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Enhancement of ultraviolet electroluminescence based on n-ZnO/n-GaN isotype heterojunction with low threshold voltage

Songzhan Li, Guojia Fang, Hao Long, Xiaoming Mo, Huihui Huang, Binzhong Dong, and Xingzhong Zhao

Appl. Phys. Lett. 96, 201111 (2010); http://dx.doi.org/10.1063/1.3431287 (3 pages) | Cited 3 times

Online Publication Date: 21 May 2010

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Ultraviolet light-emitting diodes based on simple n-ZnO/n-GaN isotype heterojunction have been fabricated using a radio frequency magnetron sputtering system. Ultraviolet emission peaking around ∼ 368 nm with a full-width at half maximum of ∼ 7 nm was observed at room temperature when the devices were under sufficient forward bias. With the presence of an i-MgO layer inserted between the ZnO and GaN layers, the ultraviolet emission intensity and output power have been much enhanced, while the threshold voltage drops down to 2.5 V. The electroluminescence mechanisms in these devices were discussed in terms of the band diagrams of the heterojunctions.
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85.60.Jb Light-emitting devices

Plasmonic mid-infrared beam steering

D. C. Adams, S. Thongrattanasiri, T. Ribaudo, V. A. Podolskiy, and D. Wasserman

Appl. Phys. Lett. 96, 201112 (2010); http://dx.doi.org/10.1063/1.3431665 (3 pages) | Cited 6 times

Online Publication Date: 21 May 2010

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We present a metal/semiconductor beam steering device for use in the mid-infrared wavelength range. We demonstrate how changing the frequency of the incident light results in a smoothly varying shift in the angular distribution of the transmitted beam, and we present an analysis of the beam profile for a number of different wavelengths. Finally we verify that a similar steering effect is achieved with fixed frequency incident light and a modification of the permittivity of the semiconductor substrate, ultimately resulting in a 3° shift in the transmitted beam angle for minimal shifts in the semiconductor permittivity.
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42.60.-v Laser optical systems: design and operation
77.22.Ch Permittivity (dielectric function)
78.66.Bz Metals and metallic alloys
78.30.-j Infrared and Raman spectra
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Mechanisms controlling the phase and dislocation density in epitaxial silicon films grown from silane below 800 °C

Charles W. Teplin, Kirstin Alberi, Maxim Shub, Carolyn Beall, Ina T. Martin, Manuel J. Romero, David L. Young, Robert C. Reedy, Paul Stradins, and Howard M. Branz

Appl. Phys. Lett. 96, 201901 (2010); http://dx.doi.org/10.1063/1.3422474 (3 pages) | Cited 4 times

Online Publication Date: 18 May 2010

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We construct a phase diagram for silicon layer growth on (001) Si by hot-wire chemical vapor deposition (HWCVD), for rates from 10 to 150 nm/min and for substrate temperatures from 500 to 800 °C. Our results show that a mixed mono and dihydride surface termination during growth causes polycrystalline growth; some H-free sites are needed for epitaxy. For epitaxial films (T>620 °C), the dislocation density decreases with increasing growth temperature because of reduced O contamination of the surface. The best HWCVD epitaxial layers have dislocation densities of 105 cm−2.
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81.05.Cy Elemental semiconductors
81.30.Dz Phase diagrams of other materials
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.ag Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

The electronic consequences of multivalent elements in inorganic solar absorbers: Multivalency of Sn in Cu2ZnSnS4

Koushik Biswas, Stephan Lany, and Alex Zunger

Appl. Phys. Lett. 96, 201902 (2010); http://dx.doi.org/10.1063/1.3427433 (3 pages) | Cited 5 times

Online Publication Date: 18 May 2010

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Multivalent transition metal impurities in semiconductors are known to create deep levels inside the band gap that are associated with changes in the oxidation state. Some emerging functional semiconductor materials now contain multivalent elements not just as impurities, but as part of their structural skeleton (“multivalent semiconductors”). This raises the possibility that the performance of such materials may be affected by those skeleton elements transitioning from one oxidation state to another, in response to charge-altering perturbations such as illumination or doping. Here we address the correlation between multivalency and the electronic properties of these new semiconductor materials.
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71.55.Ht Other nonmetals
61.72.up Other materials

Electronic structure of wurtzite and rocksalt InN investigated by optical absorption under hydrostatic pressure

J. Ibáñez, A. Segura, F. J. Manjón, L. Artús, T. Yamaguchi, and Y. Nanishi

Appl. Phys. Lett. 96, 201903 (2010); http://dx.doi.org/10.1063/1.3431291 (3 pages) | Cited 3 times

Online Publication Date: 18 May 2010

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The pressure dependence of the optical absorption edge of InN is investigated. Owing to the strong nonparabolicity of the energy bands, wurtzite InN exhibits enhanced optical absorption well above the absorption edge. The direct band gap of wurtzite InN increases linearly with pressure at 29±1 meV/GPa. The wurtzite-to-rocsksalt phase transition is observed at 15.3±0.5 GPa as a clear change in the absorption edge. We find that rocksalt InN is an indirect semiconductor with a band gap energy of around 1.0 eV. A higher energy direct transition is found at ∼ 2 eV. These results are discussed in terms of theoretical band-structure calculations.
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71.20.Nr Semiconductor compounds
62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
78.66.Fd III-V semiconductors

Strain induced suppression of silver agglomeration of indium-containing silver contact

Gwan Ho Jung, Jun Ho Son, Yang Hee Song, and Jong-Lam Lee

Appl. Phys. Lett. 96, 201904 (2010); http://dx.doi.org/10.1063/1.3430509 (3 pages) | Cited 7 times

Online Publication Date: 19 May 2010

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The mechanism for thermally stable indium-containing silver [Ag(In)] Ohmic contact on p-type GaN has been investigated. The specific contact resistivity as low as 3.8×10−5 Ω cm2 and a high reflectance of 88.4% at a 460 nm wavelength were obtained by annealing Ag(0.5 wt % In) alloy contact at 450 °C in air ambient. The In atoms in Ag matrix made In–O chemical bonds, producing a tensile stress in the film. This compensated thermal compressive stress built in the Ag film. As a result, In atoms in Ag film play a role in preventing Ag contact from agglomeration, leading to high reflectance and good thermal stability.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.35.Gy Mechanical properties; surface strains
78.40.Kc Metals, semimetals, and alloys
68.60.Bs Mechanical and acoustical properties

Dynamics of charge leakage from self-assembled CdTe quantum dots

Ł. Kłopotowski, M. Goryca, T. Kazimierczuk, P. Kossacki, P. Wojnar, G. Karczewski, and T. Wojtowicz

Appl. Phys. Lett. 96, 201905 (2010); http://dx.doi.org/10.1063/1.3430524 (3 pages)

Online Publication Date: 19 May 2010

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We study the leakage dynamics of charge stored in an ensemble of CdTe quantum dots embedded in a field-effect structure. Optically excited electrons are stored and read out by a proper time sequence of bias pulses. We monitor the dynamics of electron loss and find that the rate of the leakage is strongly dependent on time, which we attribute to an optically generated electric field related to the stored charge. A rate equation model quantitatively reproduces the results.
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78.67.Hc Quantum dots
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.21.La Quantum dots

Transient enhanced diffusion of B mediated by self-interstitials in preamorphized Ge

E. Napolitani, G. Bisognin, E. Bruno, M. Mastromatteo, G. G. Scapellato, S. Boninelli, D. De Salvador, S. Mirabella, C. Spinella, A. Carnera, and F. Priolo

Appl. Phys. Lett. 96, 201906 (2010); http://dx.doi.org/10.1063/1.3429084 (3 pages) | Cited 5 times

Online Publication Date: 19 May 2010

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The dissolution of interstitial-type end-of-range (EOR) damage in preamorphized Ge is shown to induce a transient enhanced diffusion of an epitaxially grown boron delta at temperatures above 350 °C that saturates above 420 °C. The B diffusion events are quantitatively correlated with the measured positive strain associated with the EOR damage as a function of the annealing temperature with an energy barrier for the EOR damage dissolution of 2.1±0.3 eV. These results unambiguously demonstrate that B diffuses in Ge through a mechanism assisted by self-interstitials, and impose considering the interstitial implantation damage for the modeling of impurity diffusion in Ge.
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66.30.J- Diffusion of impurities
61.72.jj Interstitials
61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si
64.75.Bc Solubility
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Effect of oxygen partial pressure on the Fermi level of ZnO1−x films fabricated by pulsed laser deposition

Chul-Hee Min, Suyeon Cho, Seung-Hyuk Lee, Deok-Yong Cho, Won Goo Park, Jae Gwan Chung, Eunha Lee, Jae Cheol Lee, Benayad Anass, Jae Hak Lee, Cheol Seong Hwang, and Se-Jung Oh

Appl. Phys. Lett. 96, 201907 (2010); http://dx.doi.org/10.1063/1.3432398 (3 pages) | Cited 2 times

Online Publication Date: 20 May 2010

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We investigated the influence of oxygen deficiency on the Fermi level (EF) of ZnO thin film prepared by pulsed laser deposition (PLD). For this purpose, we adopted in situ x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The oxygen deficiency was effectively controlled by varying the oxygen partial pressure [P(O2)] during the PLD. The EF shifted by +0.6 eV as the P(O2) decreased from 10 to 3.3 Pa. This shift indicates a significant change in the energy balance in the oxygen-deficient ZnO films. This fact suggests that the very large change in the resistivity of ZnO thin films resulting from the oxygen deficiency could be attributed to the EF shift rather than grain boundary formation in the ZnO film.
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71.20.Nr Semiconductor compounds
73.22.-f Electronic structure of nanoscale materials and related systems
68.55.ag Semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Fg Pulsed laser ablation deposition
79.60.Bm Clean metal, semiconductor, and insulator surfaces

GaN avalanche photodiodes grown on m-plane freestanding GaN substrate

Z. Vashaei, E. Cicek, C. Bayram, R. McClintock, and M. Razeghi

Appl. Phys. Lett. 96, 201908 (2010); http://dx.doi.org/10.1063/1.3432408 (3 pages) | Cited 5 times

Online Publication Date: 20 May 2010

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M-plane GaN avalanche p-i-n photodiodes on low dislocation density freestanding m-plane GaN substrates were realized using metal-organic chemical vapor deposition. High quality homoepitaxial m-plane GaN layers were developed; the root-mean-square surface roughness was less than 1 Å and the full-width-at-half-maximum value of the x-ray rocking curve for (10math0) diffraction of m-plane GaN epilayer was 32 arcsec. High quality material led to a low reverse-bias dark current of 8.11 pA for 225 μm2 mesa photodetectors prior to avalanche breakdown, with the maximum multiplication gain reaching about 8000.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Stripe/kink microstructures formed in mechanical peeling of highly orientated pyrolytic graphite

Ze Liu, Quan-shui Zheng, and Jefferson Z. Liu

Appl. Phys. Lett. 96, 201909 (2010); http://dx.doi.org/10.1063/1.3422484 (3 pages) | Cited 1 time

Online Publication Date: 20 May 2010

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Mechanical exfoliation is nowadays the primary method to produce isolated graphenes. A stripe/kink microstructure is observed in our graphite flakes produced by mechanical exfoliation of highly oriented pyrolytic graphite (HOPG). It composes a series of parallel stripes with width of about 100 microns separated by kinking microstructures ( ∼ 2 microns) in the graphite flake plane. The formation of such structure is attributed to the sliding between adjacent layers of the HOPG under the mechanical peeling. A theoretical model is presented to understand the persistence of such kinking structures in terms of the interlayer shear force locking effect.
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81.05.uf Graphite
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Formation of core/shell-like ZnSe1−xTex nanocrystals due to equilibrium surface segregation

Sumeet C. Pandey, T. J. Mountziaris, D. Venkataraman, and Dimitrios Maroudas

Appl. Phys. Lett. 96, 201910 (2010); http://dx.doi.org/10.1063/1.3428659 (3 pages) | Cited 4 times

Online Publication Date: 20 May 2010

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We report results of equilibrium surface segregation in ZnSe1−xTex nanocrystals based on a computational analysis of coupled compositional, structural, and volume relaxation of the nanocrystals that employs Monte Carlo and conjugate-gradient methods according to a first-principles-parameterized description of interatomic interactions. We have determined the equilibrium concentration distribution as a function of nanocrystal size and composition for nanocrystal morphologies that include faceted equilibrium crystal shapes. The results identify the nanoparticle size and composition ranges that allow for self-assembly of core/shell-like nanocrystal structures characterized by a Te-deficient core and a Te-rich shell.
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61.46.-w Structure of nanoscale materials
02.60.-x Numerical approximation and analysis
02.50.Ng Distribution theory and Monte Carlo studies

Site-specific electronic configurations of Fe 3d states by energy loss by channeled electrons

Kazuyoshi Tatsumi, Shunsuke Muto, Ikuo Nishida, and Ján Rusz

Appl. Phys. Lett. 96, 201911 (2010); http://dx.doi.org/10.1063/1.3429593 (3 pages) | Cited 3 times

Online Publication Date: 21 May 2010

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Site-specific configurations of Fe 3d electrons in a spinel ferrite were investigated by electron energy loss spectroscopy under electron channeling conditions. Site-specific spectra were extracted by applying a multivariate curve resolution (MCR) technique to the data set. An electronic difference in the Fe sites caused by ligand field splitting of trivalent Fe was probed. This demonstrated the promise of site-specific valence and spin state analysis in spintronics applications of spinel ferrites.
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71.20.Ps Other inorganic compounds
71.70.Ch Crystal and ligand fields
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
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Improved interfacial state density in Al2O3/GaAs interfaces using metal-organic chemical vapor deposition

Cheng-Wei Cheng and Eugene A. Fitzgerald

Appl. Phys. Lett. 96, 202101 (2010); http://dx.doi.org/10.1063/1.3428790 (3 pages) | Cited 2 times

Online Publication Date: 17 May 2010

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In situ deposition of Al2O3 on GaAs was performed by chemical-vapor-deposition (CVD) with trimethyaluminum and isopropanol as precursors. A gallium-rich region in the Al2O3 thin film above the interface was spontaneously formed via the in situ CVD process. Ga-enrichment of the interface was observed using secondary ion mass spectrometry (SIMS) depth profile measurement. X-ray photoelectron spectroscopy (XPS) results show that the gallium-rich region consists of Al2O3 and Ga2O3, but no As2O3 was observed. The Ga2O3–Al2O3 layer above the oxide/GaAs interface reduces the frequency dispersion as measured with capacitance-voltage (C-V) characteristics and lowers the interfacial state density as compared to atomic-layer-deposition *(ALD) deposited films which do not display this gallium enrichment above the interface.
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73.20.At Surface states, band structure, electron density of states
68.55.aj Insulators
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Lattice thermal transport in BaxREyCo4Sb12 (RE = Ce, Yb, and Eu) double-filled skutterudites

S. Q. Bai, X. Shi, and L. D. Chen

Appl. Phys. Lett. 96, 202102 (2010); http://dx.doi.org/10.1063/1.3429606 (3 pages) | Cited 5 times

Online Publication Date: 18 May 2010

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We use the Debye model to investigate the phonon scattering mechanisms in BaxREyCo4Sb12 double-filled skutterudites. Filling two types of guest atoms (barium and rare-earth elements) into the voids of skutterudite introduces additional phonon point defect scattering from the extra mass fluctuation at the void site, and additional phonon resonant scattering by the fillers with different vibrational frequencies, leading to significant reduction in the lattice thermal conductivity.
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72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
63.20.kp Phonon-defect interactions
61.72.Qq Microscopic defects (voids, inclusions, etc.)
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