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13 Apr 2009

Volume 94, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 151101 (2009); http://dx.doi.org/10.1063/1.3093476 (3 pages)

Nanfang Yu, Qi Jie Wang, Christian Pflügl, Laurent Diehl, Federico Capasso, Tadataka Edamura, Shinichi Furuta, Masamichi Yamanishi, and Hirofumi Kan
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Semiconductor lasers with integrated plasmonic polarizers

Nanfang Yu, Qi Jie Wang, Christian Pflügl, Laurent Diehl, Federico Capasso, Tadataka Edamura, Shinichi Furuta, Masamichi Yamanishi, and Hirofumi Kan

Appl. Phys. Lett. 94, 151101 (2009); http://dx.doi.org/10.1063/1.3093476 (3 pages) | Cited 22 times

Online Publication Date: 13 April 2009

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The authors reported the plasmonic control of semiconductor laser polarization by means of metallic gratings and subwavelength apertures patterned on the laser emission facet. An integrated plasmonic polarizer can project the polarization of a semiconductor laser onto other directions. By designing a facet with two orthogonal grating-aperture structures, a polarization state consisting of a superposition of a linearly and right-circularly polarized light was demonstrated in a quantum cascade laser; a first step toward a circularly polarized laser.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.82.Gw Other integrated-optical elements and systems

Giant enhancement of top emission from ZnO thin film by nanopatterned Pt

K. W. Liu, Y. D. Tang, C. X. Cong, T. C. Sum, A. C. H. Huan, Z. X. Shen, Li Wang, F. Y. Jiang, X. W. Sun, and H. D. Sun

Appl. Phys. Lett. 94, 151102 (2009); http://dx.doi.org/10.1063/1.3116617 (3 pages) | Cited 28 times

Online Publication Date: 13 April 2009

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The authors report the enhancement of the bandgap emission from ZnO thin films by surface modification and surface plasmon cross-coupling. 12-fold and twofold enhancements of bandgap emission from the metal side of ZnO film were observed by sputtering Pt nanopattern and Pt film onto ZnO film, respectively. Time-resolved photoluminescence indicates that the decay time is slowed down by Pt capping, contrary to common observations. The “abnormal” phenomena are interpreted by considering both the surface modification and surface plasmon coupling.
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81.07.Bc Nanocrystalline materials
81.16.Rf Micro- and nanoscale pattern formation
78.55.Et II-VI semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations

Near-field imaging of coupled photonic-crystal microcavities

Silvia Vignolini, Francesca Intonti, Margherita Zani, Francesco Riboli, Diederik S. Wiersma, Lianhe H. Li, Laurent Balet, Marco Francardi, Annamaria Gerardino, Andrea Fiore, and Massimo Gurioli

Appl. Phys. Lett. 94, 151103 (2009); http://dx.doi.org/10.1063/1.3107269 (3 pages) | Cited 17 times

Online Publication Date: 14 April 2009

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We report by means of near-field microscopy on the coupling between two adjacent photonic crystal microcavities. Clear-cut experimental evidence of the spatial delocalization of coupled-cavity optical modes is obtained by imaging the electromagnetic local density of states. We also demonstrate that it is possible to design photonic structures with selective coupling between different modes having orthogonal spatial extensions
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.70.Qs Photonic bandgap materials
07.60.Pb Conventional optical microscopes
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Substrate emitting index coupled quantum cascade lasers using biperiodic top metal grating

G. Maisons, M. Carras, M. Garcia, O. Parillaud, B. Simozrag, X. Marcadet, and A. De Rossi

Appl. Phys. Lett. 94, 151104 (2009); http://dx.doi.org/10.1063/1.3113524 (3 pages) | Cited 7 times

Online Publication Date: 14 April 2009

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We report on the design and experimental demonstration of a specific metal grating profile that enables a substrate emission of a quantum cascade laser. A low loss, index coupled, and horizontal cavity surface emitting laser (HCSEL) design is proposed, which is very robust against technological spreads. The detailed analysis of the metallic top grating is performed, enabling the laser still to operate as a distributed feedback laser while emitting from the substrate. Following this concept, HCSEL with InP cladding layers and InGaAs/AlInAs active regions have been fabricated. Room temperature HCSEL emitting at 5.65 μm with a low beam divergence is demonstrated.
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42.55.Px Semiconductor lasers; laser diodes

Bulk photonic metamaterial with hyperbolic dispersion

M. A. Noginov, Yu. A. Barnakov, G. Zhu, T. Tumkur, H. Li, and E. E. Narimanov

Appl. Phys. Lett. 94, 151105 (2009); http://dx.doi.org/10.1063/1.3115145 (3 pages) | Cited 23 times

Online Publication Date: 14 April 2009

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We have demonstrated the thickest bulk photonic metamaterial reported in the literature based on an Ag-filled alumina membrane. The material is highly anisotropic with hyperbolic dispersion at λ>0.84 μm. The refraction of light in the direction expected of isotropic media with n<1 has been experimentally demonstrated at λ = 632.8 nm. This makes the material potentially suitable for a variety of applications ranging from subdiffraction imaging to optical cloaking.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

High-performance injectorless quantum cascade lasers emitting below 6 μm

Simeon Katz, Augustinas Vizbaras, Gerhard Boehm, and Markus-Christian Amann

Appl. Phys. Lett. 94, 151106 (2009); http://dx.doi.org/10.1063/1.3119184 (2 pages) | Cited 11 times

Online Publication Date: 14 April 2009

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An injectorless quantum cascade laser emitting around 5.7 μm with more than 1 W of output power and a wall-plug efficiency of 3.6% at room temperature in pulsed operation is presented. The active region of the device is a design that picked up the idea of the four-alloy structure, which has already lead to very low threshold current densities. The pulsed threshold current densities were measured as low as 1.1 kA/cm2 at room temperature for an as-cleaved 3.6 mm long device, and 0.93 kA/cm2 for a high-reflection-coated 4 mm long device.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.By Design of specific laser systems

Continuous wave second-harmonic generation using domain-disordered quasi-phase matching waveguides

Sean J. Wagner, Barry M. Holmes, Usman Younis, Amr S. Helmy, J. Stewart Aitchison, and David C. Hutchings

Appl. Phys. Lett. 94, 151107 (2009); http://dx.doi.org/10.1063/1.3119629 (3 pages) | Cited 5 times

Online Publication Date: 14 April 2009

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Second-harmonic generation in domain-disordered quasi-phase-matched GaAs/AlGaAs superlattice-core waveguides was demonstrated using a continuous wave fundamental source. Output second-harmonic powers of up to 1.6 μW were measured when on a Fabry-Pérot resonance peak. Temperature-related bistable behavior was observed in both the fundamental and second-harmonic output when tuning either the input power or input wavelength.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Wc Optical coatings

Atomic clock based on transient coherent population trapping

Tao Guo, Ke Deng, Xuzong Chen, and Zhong Wang

Appl. Phys. Lett. 94, 151108 (2009); http://dx.doi.org/10.1063/1.3120278 (3 pages) | Cited 1 time

Online Publication Date: 15 April 2009

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We proposed a scheme to implement coherent population trapping (CPT) atomic clock based on the transient CPT phenomenon. We proved that the transient transmitted laser power in a typical Λ system near CPT resonance features as a damping oscillation. Also, the oscillating frequency is exactly equal to the frequency detuning from the atomic hyperfine splitting. Therefore, we can directly measure the frequency detuning and then compensated to the output frequency of microwave oscillator to get the standard frequency. By this method, we can further simplify the structure of CPT atomic clock, and make it easier to be digitized and miniaturized.
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06.30.Ft Time and frequency
32.10.Fn Fine and hyperfine structure
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
32.80.-t Photoionization and excitation
06.20.fb Standards and calibration

Nonequilibrium Green’s function calculation for four-level scheme terahertz quantum cascade lasers

H. Yasuda, T. Kubis, P. Vogl, N. Sekine, I. Hosako, and K. Hirakawa

Appl. Phys. Lett. 94, 151109 (2009); http://dx.doi.org/10.1063/1.3119312 (3 pages) | Cited 13 times

Online Publication Date: 15 April 2009

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We have calculated the performance of a recently proposed four-level scheme terahertz quantum cascade laser (4L terahertz-QCL) with the nonequilibrium Green’s function method. The calculation result for 40 K showed that the 4L QCL has a larger terahertz gain than the conventional resonant phonon QCL. This is because a large number of electrons accumulate in the upper lasing level and contribute to lasing in the new scheme. When the temperature is increased, the advantage of gain decreases due to thermally activated phonon scattering.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Diffracted magneto-optical Kerr effect in one-dimensional magnetic gratings

J. B. Kim, Y. H. Lu, M. H. Cho, G. J. Lee, Y. P. Lee, J. Y. Rhee, and C. S. Yoon

Appl. Phys. Lett. 94, 151110 (2009); http://dx.doi.org/10.1063/1.3120268 (3 pages) | Cited 2 times

Online Publication Date: 16 April 2009

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One-dimensional Co2MnSi magnetic gratings were fabricated with a significant ease by using the interference pattern of two femtosecond-laser beams which resulted in a selective-area annealing of the as-deposited Co2MnSi film. The longitudinal Kerr rotation of the negative first-order diffracted beam was nearly 30 times larger than that of the zeroth-order one in a sample fabricated with the optimal conditions. The enhancement strongly depends on the grating depth, which varies with the number of laser shots, confirming the theoretical result that the magneto-optical Kerr-effect enhancement is reduced as the grating depth increases.
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42.79.Dj Gratings
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
81.40.Gh Other heat and thermomechanical treatments

Giant optical resonances due to gain-assisted Bloch surface plasmons

Andrey Kobyakov, Aramais R. Zakharian, Krishna M. Gundu, and Sergey A. Darmanyan

Appl. Phys. Lett. 94, 151111 (2009); http://dx.doi.org/10.1063/1.3120564 (3 pages) | Cited 4 times

Online Publication Date: 16 April 2009

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We theoretically study Bloch surface plasmon (BSP) resonances in a thin subwavelength-structured metallic film adjacent to a submicron dielectric layer with gain. We show that for a planar gold-silver bimetallic grating resonant excitation of a BSP with the optimum value of gain may result in giant amplification of both transmitted and reflected waves. We explain the effect and illustrate how the electromagnetic near-field structure determines the type of interference (constructive or destructive) between the eigenmodes of the system, which results in either strong enhancement or suppression of the scattered waves.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces

Nonplanar chiral metamaterials with negative index

Bingnan Wang, Jiangfeng Zhou, Thomas Koschny, and Costas M. Soukoulis

Appl. Phys. Lett. 94, 151112 (2009); http://dx.doi.org/10.1063/1.3120565 (3 pages) | Cited 15 times

Online Publication Date: 16 April 2009

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We demonstrate experimentally and numerically that nonplanar chiral metamaterials give giant optical activity, circular dichroism, and negative refractive index. The transmission, reflection, and the retrieval results of the experiments agree pretty well with the simulations. This is an important step toward the design and fabrication of three-dimensional isotropic chiral metamaterials.
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42.70.-a Optical materials
33.55.+b Optical activity and dichroism
42.25.Bs Wave propagation, transmission and absorption
42.25.Gy Edge and boundary effects; reflection and refraction

Photoelectrochemical etching of p-type GaN heterostructures

Adele C. Tamboli, Asako Hirai, Shuji Nakamura, Steven P. DenBaars, and Evelyn L. Hu

Appl. Phys. Lett. 94, 151113 (2009); http://dx.doi.org/10.1063/1.3120545 (3 pages) | Cited 10 times

Online Publication Date: 17 April 2009

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We have developed a method for photoelectrochemical etching of p-type semiconductors, including GaN, that relies on the built-in bandbending already inherent to optical devices. Electron-hole pairs are generated by filtered light in a buried small bandgap layer, and a pn junction separates the charge. Electrons are sent into the n-type layer, where they are extracted, and holes to the surface, where they participate in etching reactions. This technique is rapid and inexpensive, and it requires no applied bias or elevated temperatures. This technique has widespread applications to GaN optical devices where ion-damage-free etching or wide tunability of etch parameters is desired.
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81.65.Cf Surface cleaning, etching, patterning
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
82.45.Vp Semiconductor materials in electrochemistry
82.50.-m Photochemistry

Metallic-like photoluminescence and absorption in fused silica surface flaws

Ted A. Laurence, Jeff D. Bude, Nan Shen, Theodore Feldman, Philip E. Miller, William A. Steele, and Tayyab Suratwala

Appl. Phys. Lett. 94, 151114 (2009); http://dx.doi.org/10.1063/1.3119622 (3 pages) | Cited 15 times

Online Publication Date: 17 April 2009

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Using high-sensitivity confocal time-resolved photoluminescence (PL) techniques, we report an ultrafast PL (40 ps–5 ns) from impurity-free surface flaws on fused silica, including polished, indented, or fractured surfaces of fused silica, and from laser-heated evaporation pits. This PL is excited by the single-photon absorption of sub-band gap light, and is especially bright in fractures. Regions which exhibit this PL are strongly absorptive well below the band gap, as evidenced by a propensity to damage with 3.5 eV nanosecond-scale laser pulses.
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78.55.Hx Other solid inorganic materials
78.47.jd Time resolved luminescence
81.65.Ps Polishing, grinding, surface finishing
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mm Fracture
71.20.Ps Other inorganic compounds
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Raman spectroscopy of reaction fields induced by plasma in supercritical CO2

Takaaki Tomai, Hiroharu Yui, and Kazuo Terashima

Appl. Phys. Lett. 94, 151501 (2009); http://dx.doi.org/10.1063/1.3116622 (3 pages) | Cited 5 times

Online Publication Date: 13 April 2009

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The characteristic microstructures of supercritical fluids, such as density fluctuation near the critical point, in reaction fields induced by low-temperature plasma were investigated by using Raman spectroscopy. It was found that the decrease in the density of CO2 during plasma generation was less than 0.02 g/cm3 (critical density of CO2:0.467 g/cm3), when compared to the decrease in density of pure CO2 for a wide pressure range from gaseous to supercritical conditions. Moreover, it was experimentally verified that the density fluctuation observed near the critical point persists in the reaction field.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.25.Gj Fluctuation and chaos phenomena

Spatial nonuniformity of electron energy in a microwave atmospheric-pressure microplasma

Li-Guo Zhu, Zhi-Bo Zhang, Xi-Ming Zhu, Yi-Kang Pu, and Ze-Ren Li

Appl. Phys. Lett. 94, 151502 (2009); http://dx.doi.org/10.1063/1.3119316 (3 pages) | Cited 4 times

Online Publication Date: 15 April 2009

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The characteristics of the electron energy in a microwave atmospheric-pressure argon microplasma are investigated by a spatially resolved optical emission spectroscopy. By adding tiny amount of xenon (<1 ppm) as tracer gas into the argon discharge, it is found that the spatial distribution of the electrons with energy >8.3 eV is quite different from that of the electrons with energy >11.5 eV. Spatial distribution of the population ratio between 4p and 5p levels of Ar atom is also determined. Furthermore, with a collisional-radiative model, it is found that the spatial variation of this population ratio is mainly attributed to the spatial nonuniformity of the effective electron temperature.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.20.-j Elementary processes in plasmas
52.25.-b Plasma properties

Experimental verification of Boltzmann equilibrium for negative ions in weakly collisional electronegative plasmas

Young-chul Ghim(Kim) and Noah Hershkowitz

Appl. Phys. Lett. 94, 151503 (2009); http://dx.doi.org/10.1063/1.3119627 (3 pages) | Cited 18 times

Online Publication Date: 15 April 2009

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Weakly collisional Ar–O2 electronegative plasmas are investigated in a dc multidipole chamber. An electronegative core and an electropositive halo are observed. The density ratio of negative ions to electrons (α) in the nondrifting bulk is found to be 0.43. The profile of α is found using both the phase velocity of ion acoustic waves and the drift velocity of positive ions determined by laser-induced fluorescence. The experiment shows that negative ions are in Boltzmann equilibrium with a temperature of 0.06±0.02 eV. Double layers are not found separating the electronegative core and the electropositive halo.
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52.20.-j Elementary processes in plasmas
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Structural, dielectric, and optical properties of yttrium calcium borate glasses

Cristiane N. Santos, Domingos De Sousa Meneses, Patrick Echegut, Daniel R. Neuville, Antonio C. Hernandes, and Alain Ibanez

Appl. Phys. Lett. 94, 151901 (2009); http://dx.doi.org/10.1063/1.3115796 (3 pages) | Cited 8 times

Online Publication Date: 14 April 2009

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Structural and optical properties of stable glasses in the Y2O3–CaO–B2O3 system, containing the same Y/Ca ratio as the YCa4O(BO3)3 (YCOB) crystal, were determined from Raman and reflectance infrared spectroscopy. Changes in optical functions with composition are associated with an increase in the number of non-bridging oxygen and to calcium/yttrium oxides content. Refractive indexes values (from 1.597 to 1.627 at λ = 2 μm) are in good agreement with those of the YCOB crystal, an indication that these glasses are potential candidates for optical applications due to their ease of shaping as large bulk samples or fibers.
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61.43.Fs Glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Photoreflectance study of the energy gap and spin-orbit splitting in InNAs alloys

R. Kudrawiec, J. Misiewicz, Q. Zhuang, A. M. R. Godenir, and A. Krier

Appl. Phys. Lett. 94, 151902 (2009); http://dx.doi.org/10.1063/1.3117239 (3 pages) | Cited 7 times

Online Publication Date: 14 April 2009

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Photoreflectance spectroscopy has been applied to study the energy gap and the spin-orbit splitting in InNAs alloys with the nitrogen concentration changing from 0% to 0.88%. It has been observed that the energy gap of InNAs decreases with the increase in nitrogen concentration (about 60 meV per 1% of nitrogen) but the spin-orbit splitting almost does not change. It shows that nitrogen atoms in InNAs alloys influence mainly the conduction band, i.e., shift this band toward the valence band. The bowing parameter for the energy gap and spin-orbit splitting has been determined to be 7.3±0.6 and −0.7±0.4 eV, respectively.
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71.20.Nr Semiconductor compounds
78.20.Bh Theory, models, and numerical simulation
61.72.sd Impurity concentration
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Ordered amorphous silicon nanoisland arrays and reflection spectral dependence on nanoisland geometrical parameters

L. Z. Liu, G. S. Huang, L. L. Wang, T. H. Li, and X. L. Wu

Appl. Phys. Lett. 94, 151903 (2009); http://dx.doi.org/10.1063/1.3119319 (3 pages) | Cited 4 times

Online Publication Date: 14 April 2009

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We report an anodic porous alumina mask technique for fabricating orderly hemispherical silicon nanoisland arrays with island diameters of 30–120 nm. Reflection spectral measurements show that the phase transition of incident light can periodically be transferred with changes in geometrical parameters of the ordered arrays. Thus the redshift of the reflection peak with decreasing both sizes of the nanoislands and incident angle of light wave can be explained well on the basis of a modified rigorous vector coupled-wave theory. The simple fabrication technique and reflection spectral redshift of the ordered arrays have potential applications in optical devices and solar cells.
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78.66.Db Elemental semiconductors and insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
84.60.Jt Photoelectric conversion
64.70.K- Solid-solid transitions
81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials

Ab initio study of lithium and sodium iron fluorophosphate cathodes for rechargeable batteries

M. Ramzan, S. Lebègue, and R. Ahuja

Appl. Phys. Lett. 94, 151904 (2009); http://dx.doi.org/10.1063/1.3119704 (3 pages) | Cited 6 times

Online Publication Date: 14 April 2009

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The cathode materials Li2FePO4F and Na2FePO4F are studied by means of ab initio calculations. The generalized gradient approximation (GGA) and GGA+U are used to describe the crystal structures, and the electronic and magnetic properties of Li2FePO4F, Na2FePO4F, LiFePO4F, and NaFePO4F. Since only the lattice parameters are known for Li2FePO4F, our calculations predict the corresponding atomic positions, and reveal that the iron atom state (FeIII or FeII) is changed during the reaction, which is of importance to understand the reactions taking place in rechargeable batteries. Finally, our calculated intercalation voltage with the GGA+U approximation is in good agreement with experimental value.
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61.66.Fn Inorganic compounds
82.45.Fk Electrodes
82.47.Aa Lithium-ion batteries

Large plasticity and tensile necking of Zr-based bulk-metallic-glass-matrix composites synthesized by the Bridgman solidification

J. W. Qiao, S. Wang, Y. Zhang, P. K. Liaw, and G. L. Chen

Appl. Phys. Lett. 94, 151905 (2009); http://dx.doi.org/10.1063/1.3118587 (3 pages) | Cited 36 times

Online Publication Date: 14 April 2009

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The microstructures of the in situ bulk-metallic-glass-matrix composites are usually controlled by changing the alloy compositions. In this paper, Zr-based bulk-metallic-glass-matrix composites containing dendrites with a fixed composition of Zr37.5Ti32.2Nb7.2Cu6.1Be17.0 are synthesized by the Bridgman solidification. The sizes and volume fractions of dendrites in the composites are controlled by adjusting the withdrawal velocities. A linear relationship between the spanning lengths of individual dendrites and the withdrawal velocities is established. Large plasticity and tensile necking can be obtained by only controlling the cooling condition.
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81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
81.30.Fb Solidification
81.20.-n Methods of materials synthesis and materials processing

Growth of high quality N-polar AlN(000math) on Si(111) by plasma assisted molecular beam epitaxy

Sansaptak Dasgupta, F. Wu, J. S. Speck, and U. K. Mishra

Appl. Phys. Lett. 94, 151906 (2009); http://dx.doi.org/10.1063/1.3118593 (3 pages) | Cited 16 times

Online Publication Date: 14 April 2009

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High quality N-polar AlN epilayers were grown and characterized on Si(111) substrates by plasma assisted molecular beam epitaxy as a first step toward growth of N-polar nitrides on Si(111). Polarity inversion to N-face by an optimized predeposition of Al adatoms on the reconstructed 7×7 Si(111) surface was investigated. Al adatoms can saturate the dangling bonds of Si atoms, resulting in growth of AlN in (000math) direction on subsequent exposure to N2 plasma. N-polarity was confirmed by observing strong 3×3 and 6×6 reflection high-energy electron diffraction reconstructions, convergent beam electron diffraction imaging and KOH etching studies. The structural properties were investigated by x-ray diffraction measurements, cross section and plan-view TEM studies.
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68.55.ag Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Og High-resolution transmission electron microscopy (HRTEM)
81.65.Cf Surface cleaning, etching, patterning
68.43.Mn Adsorption kinetics
81.05.Ea III-V semiconductors
68.35.bg Semiconductors

Positron annihilation in (Ga, Mn)N: A study of vacancy-type defects

X. L. Yang, W. X. Zhu, C. D. Wang, H. Fang, T. J. Yu, Z. J. Yang, G. Y. Zhang, X. B. Qin, R. S. Yu, and B. Y. Wang

Appl. Phys. Lett. 94, 151907 (2009); http://dx.doi.org/10.1063/1.3120267 (3 pages) | Cited 3 times

Online Publication Date: 15 April 2009

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The vacancy-type defects in (Ga,Mn)N films grown by metal organic chemical vapor deposition were studied by positron annihilation technique. Doppler broadening spectra were measured for the films. Compared to the undoped GaN film, the positron trapping defects in the (Ga,Mn)N films have been changed to a new type defects and its concentration increases with the increasing Mn concentration. By analyzing the S-W correlation plots and our previous results, we identify this type defects in the (Ga,Mn)N as VN-MnGa complex. This type of defects should be considered when understand the magnetic properties in a real (Ga,Mn)N system.
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61.80.Fe Electron and positron radiation effects
81.05.Ea III-V semiconductors
61.72.jd Vacancies
61.72.uj III-V and II-VI semiconductors
78.70.Bj Positron annihilation
75.50.Pp Magnetic semiconductors

ZnO glass-ceramics: An alternative way to produce semiconductor materials

Hirokazu Masai, Tatsuya Toda, Takahiro Ueno, Yoshihiro Takahashi, and Takumi Fujiwara

Appl. Phys. Lett. 94, 151908 (2009); http://dx.doi.org/10.1063/1.3120282 (3 pages) | Cited 7 times

Online Publication Date: 15 April 2009

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Fabrication of transparent glass-ceramics containing ZnO nanocrystallites has been reported. The obtained material shows UV-excited photoluminescence consisting of both broad emission in the visible region and the free exciton emission at 3.28 eV. Since the observed emission depends on the precipitated state of ZnO in the glass matrix, the glass-ceramics obtained by this way will give an alternative selection of semiconductor material with unique optical and electronic functions.
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81.05.Pj Glass-based composites, vitroceramics
81.07.Bc Nanocrystalline materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Hx Other solid inorganic materials
71.35.-y Excitons and related phenomena
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