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13 Nov 2006

Volume 89, Issue 20, Articles (20xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 202101 (2006); http://dx.doi.org/10.1063/1.2388049 (3 pages)

J. H. Lee, Zh. M. Wang, N. W. Strom, Yu. I. Mazur, and G. J. Salamo
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Tunable plasma wave resonant detection of optical beating in high electron mobility transistor

J. Torres, P. Nouvel, A. Akwoue-Ondo, L. Chusseau, F. Teppe, A. Shchepetov, and S. Bollaert

Appl. Phys. Lett. 89, 201101 (2006); http://dx.doi.org/10.1063/1.2388142 (3 pages) | Cited 15 times

Online Publication Date: 13 November 2006

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The authors report on tunable terahertz resonant detection of two 1.55 μm cw lasers beating by plasma waves in AlGaAs/InGaAs/InP high electron mobility transistor. The authors show that the fundamental plasma resonant frequency and its odd harmonics can be tuned with the applied gate voltage in the range of 75–490 GHz. The observed frequency dependence on gate bias is found to be in good agreement with the theoretical plasma wave dispersion law.
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85.30.Tv Field effect devices

Strong resonant luminescence from Ge quantum dots in photonic crystal microcavity at room temperature

J. S. Xia, Y. Ikegami, Y. Shiraki, N. Usami, and Y. Nakata

Appl. Phys. Lett. 89, 201102 (2006); http://dx.doi.org/10.1063/1.2386915 (3 pages) | Cited 32 times

Online Publication Date: 13 November 2006

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Freestanding hexagonal two-dimensional photonic crystal (PhC) microcavities with Ge self-assembled quantum dots were fabricated on silicon-on-insulator substrates. Strong photoluminescence associated with Ge quantum dots was observed in the wavelength region of 1.2–1.6 μm at room temperature. Sharp peaks dominated the spectrum, showing strong optical resonance inside the cavity. A resonant peak with a quality factor of 560 was observed at 1.58 μm along with a significant enhancement of the luminescence in the microphotoluminescence spectrum. The peaks were also observed to reasonably shift when the structural parameter of PhC was changed.
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78.67.Hc Quantum dots
78.66.Db Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
42.70.Qs Photonic bandgap materials

Single-mode operation in the slow-light regime using oscillatory waves in generalized left-handed heterostructures

Kosmas L. Tsakmakidis, Andreas Klaedtke, Durga P. Aryal, Cécile Jamois, and Ortwin Hess

Appl. Phys. Lett. 89, 201103 (2006); http://dx.doi.org/10.1063/1.2387873 (3 pages) | Cited 27 times

Online Publication Date: 13 November 2006

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The authors present an exact, analytic study of oscillatory modes guided by generalized asymmetric two-dimensional planar heterostructures with negative refractive index in either the core or the cladding. It is shown that, in sharp contrast to normal dielectric configurations, these waveguides always possess a frequency region where the second-order oscillatory mode may exist alone and allow for attaining zero group velocity under weak guidance conditions. In addition the mode has a field distribution that renders it excitable with an end-fire approach, making such structures attractive for applications requiring slow light. Advantages compared to previous methods of slowing or stopping light are discussed.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.79.Gn Optical waveguides and couplers
42.70.-a Optical materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Improvement of near-ultraviolet nitride-based light emitting diodes with mesh indium tin oxide contact layers

C. H. Kuo, C. M. Chen, C. W. Kuo, C. J. Tun, C. J. Pan, B. J. Pong, and G. C. Chi

Appl. Phys. Lett. 89, 201104 (2006); http://dx.doi.org/10.1063/1.2387941 (3 pages) | Cited 9 times

Online Publication Date: 13 November 2006

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The authors have demonstrated nitride-based near-ultraviolet (NUV) light emitting diodes (LEDs) with mesh indium tin oxide (ITO) contact layer. With 20 mA injection current, it was found that forward voltages were 3.94 and 4.05 V while the output powers were 7.54 and 9.02 mW for the planar ITO LED and mesh ITO LED, respectively. The larger LED output power should be attributed partially to the reduced absorption of ITO in the NUV region and partially to the better current spreading.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Near-infrared imprinted distributed feedback lasers

P. Del Carro, A. Camposeo, R. Stabile, E. Mele, L. Persano, R. Cingolani, and D. Pisignano

Appl. Phys. Lett. 89, 201105 (2006); http://dx.doi.org/10.1063/1.2387974 (3 pages) | Cited 21 times

Online Publication Date: 13 November 2006

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The authors report on the fabrication and characterization of an organic distributed feedback laser operating in the near infrared. The device, fabricated by room-temperature nanoimprint lithography, is based on an organic dye hosted by a poly(methylmethacrylate) matrix. The laser emission from an imprinted 620 nm period grating is peaked at 918 nm with a linewidth of 8 Å and a pumping threshold of 37 μJ/cm2, and it is strongly polarized with a polarization contrast as high as 0.99. The lasing wavelength is tunable in the range of 890–930 nm by adjusting the grating period, and the operational lifetime is up to 6×103 excitation pulses in vacuum environment. These results demonstrate the possibility of realizing imprinted organic-based near-infrared lasers, thus approaching spectral regions relevant for optical communication applications.
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42.55.Mv Dye lasers
42.60.Fc Modulation, tuning, and mode locking
42.60.By Design of specific laser systems
81.16.Nd Micro- and nanolithography

Optical probes based on optical fibers and single-walled carbon nanotubes for hydrogen detection at cryogenic temperatures

A. Cusano, M. Consales, A. Cutolo, M. Penza, P. Aversa, M. Giordano, and A. Guemes

Appl. Phys. Lett. 89, 201106 (2006); http://dx.doi.org/10.1063/1.2370292 (3 pages) | Cited 9 times

Online Publication Date: 13 November 2006

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In this letter, preliminary results on the feasibility to use optical fiber sensors coated by single-walled carbon nanotubes (SWCNTs)-based sensitive materials for hydrogen detection at cryogenic temperatures are presented. The optical probes have been realized by the Langmuir-Blodgett deposition of close-end and open-end SWCNTs on the distal end of standard optical fibers. The results obtained from hydrogen detection testing, carried out at a temperature as low as 113 K, demonstrate the excellent potentiality of the proposed configuration to sense very low percentages of gaseous hydrogen (<5%), with good recovery and reversibility features as well as fast response times.
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42.81.Pa Sensors, gyros
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Area-tunable micromirror based on electrowetting actuation of liquid-metal droplets

Zhiliang Wan, Hongjun Zeng, and Alan Feinerman

Appl. Phys. Lett. 89, 201107 (2006); http://dx.doi.org/10.1063/1.2388943 (3 pages) | Cited 11 times

Online Publication Date: 14 November 2006

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The authors report a micromirror device actuated by electrowetting effect. The micromirror surface is formed by a liquid-metal droplet jetted on a substrate and then topped with a parylene/Teflon coated indium tin oxide glass slide. The droplet is deformed by a voltage applied across the parylene/Teflon film. The radius of micromirror is tuned from 13 μm (0 V) to 88 μm (90 V), and the normalized area increases from 0.2 to 0.94 accordingly. The switching time ranges from 1 ms for a 350 μm diameter droplet to 0.2 ms for a 50 μm one. A 4×1 micromirror array is demonstrated and switched simultaneously.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.82.Gw Other integrated-optical elements and systems
42.79.Bh Lenses, prisms and mirrors
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Low threshold blue conjugated polymer lasers with first- and second-order distributed feedback

C. Karnutsch, C. Gýrtner, V. Haug, U. Lemmer, T. Farrell, B. S. Nehls, U. Scherf, J. Wang, T. Weimann, G. Heliotis, C. Pflumm, J. C. deMello, and D. D. C. Bradley

Appl. Phys. Lett. 89, 201108 (2006); http://dx.doi.org/10.1063/1.2390644 (3 pages) | Cited 33 times

Online Publication Date: 14 November 2006

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We report on the fabrication of low threshold distributed feedback (DFB) polymer lasers based on a polyfluorene derivative containing statistical binaphthyl units (BN-PFO). First- and second-order feedback lasers have been realized. The emission was tuned in the wavelength range from 438 to 459 nm by varying the grating period and the film thickness. A threshold energy of 280 pJ/pulse was observed in second-order DFB structures, which could be further reduced to 160 pJ/pulse by employing first-order feedback in electron beam lithographically patterned structures with a period of 140 nm. In these first-order structures, laser oscillation at both edges of the photonic stop band was observed. These very low threshold values render BN-PFO a very promising material for future electrically pumped organic semiconductor laser diodes.
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42.55.-f Lasers
42.60.By Design of specific laser systems
42.70.Jk Polymers and organics
42.70.Hj Laser materials
42.60.Fc Modulation, tuning, and mode locking

Analysis of defects in an electric and photonic double-layer substrate made by separation-by-implanted-oxygen three-dimensional sculpting

Koichiro Kishima

Appl. Phys. Lett. 89, 201109 (2006); http://dx.doi.org/10.1063/1.2388882 (3 pages) | Cited 1 time

Online Publication Date: 16 November 2006

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With a view to application to electric-device fabrication, the authors investigated a separation-by-implanted-oxygen (SIMOX) three-dimensional (3D) sculpting method [ P. Koonath et al., Appl. Phys. Lett. 83, 4909 (2003) ] that will integrate in three dimensions electric circuits and photonic circuits on a silicon-on-insulator substrate. The authors analyzed the defects in the first silicon layer for electric circuits and the second silicon layer for optical circuits made by SIMOX 3D sculpting. The authors found that a balance between an acceptable number of defects on the first silicon layer and the formation of a buried optical waveguide is achievable. The defect densities of the first silicon layer and the second silicon layer were 1.8×103/cm2 and 5.0×107/cm2, respectively.
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42.82.Et Waveguides, couplers, and arrays
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Gn Optical waveguides and couplers
85.60.-q Optoelectronic devices
71.55.Cn Elemental semiconductors

Temperature mapping and thermal lensing in large-mode, high-power laser diodes

P. K. L. Chan, K. P. Pipe, J. J. Plant, R. B. Swint, and P. W. Juodawlkis

Appl. Phys. Lett. 89, 201110 (2006); http://dx.doi.org/10.1063/1.2388884 (3 pages) | Cited 3 times

Online Publication Date: 16 November 2006

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The authors use high-resolution charge-coupled device based thermoreflectance to derive two dimensional facet temperature maps of a λ = 1.55 μm InGaAsP/InP watt-class laser that has a large (>5×5 μm2) fundamental optical mode. Recognizing that temperature rise in the laser will lead to refractive index increase, they use the measured temperature profiles as an input to a finite-element mode solver, predicting bias-dependent spatial mode behavior that agrees well with experimental observations. These results demonstrate the general usefulness of high-resolution thermal imaging for studying spatial mode dynamics in photonic devices.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Single-mode room-temperature emission with a silicon rod lattice

B. Cluzel, V. Calvo, T. Charvolin, E. Picard, P. Noé, and E. Hadji

Appl. Phys. Lett. 89, 201111 (2006); http://dx.doi.org/10.1063/1.2364876 (3 pages) | Cited 6 times

Online Publication Date: 16 November 2006

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The authors experimentally evidence an increase of light emission efficiency at room temperature in a silicon-on-insulator photonic crystal. The photonic crystal is made of a triangular lattice of silicon rods and operates as a single-mode light extractor. It exhibits a luminescence intensity two orders of magnitude higher than silicon-on-insulator substrate. In light of photoluminescence experiments, emission diagram measurements, and finite difference time domain calculations, they identify the different optical properties of the photonic crystal and they demonstrate the existence of at least a fivefold emission efficiency enhancement per surface unit.
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42.70.Qs Photonic bandgap materials
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators

Lowering lasing threshold in ferroelectric liquid crystal sandwiched between dielectric multilayers

Yuko Matsuhisa, Wolfgang Haase, Akihiko Fujii, and Masanori Ozaki

Appl. Phys. Lett. 89, 201112 (2006); http://dx.doi.org/10.1063/1.2369539 (3 pages) | Cited 2 times

Online Publication Date: 16 November 2006

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The authors have investigated laser action in ferroelectric liquid crystal (FLC) sandwiched between dielectric multilayers composed of SiO2 and TiO2. The single-mode laser action was observed at the band edge of FLC. The lasing threshold was much lower than that of simple FLC because of the double optical confinement caused by the sandwich structure. They have also demonstrated the tuning of lasing wavelength by applying an electric field.
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42.70.Df Liquid crystals
42.70.Hj Laser materials
61.30.-v Liquid crystals
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
78.20.Jq Electro-optical effects

Compact, low-cost, and high-resolution interrogation unit for optical sensors

Peter Kiesel, Oliver Schmidt, Setu Mohta, Noble Johnson, and Stefan Malzer

Appl. Phys. Lett. 89, 201113 (2006); http://dx.doi.org/10.1063/1.2390650 (3 pages) | Cited 2 times

Online Publication Date: 16 November 2006

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Compact wavelength detectors that resolve wavelength changes in the subpicometer range over a broad spectral range are presented. A photodiode array or position sensor device is coated with a linear variable filter that converts the wavelength of the incident light into a spatial intensity distribution. The centroid of the spatial distribution is determined by a differential readout of the two elements of the photodiode array or the position sensor device. The device can interrogate any optical sensor that produces a wavelength shift in response to a stimulus. The potential of this device was tested by interrogating fiber-Bragg-grating sensors.
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42.81.Pa Sensors, gyros
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Room-temperature InAsSbP/InAs light emitting diodes by liquid phase epitaxy for midinfrared (3–5 μm) dynamic scene projection

V. K. Malyutenko, O. Yu. Malyutenko, and A. V. Zinovchuk

Appl. Phys. Lett. 89, 201114 (2006); http://dx.doi.org/10.1063/1.2390655 (3 pages) | Cited 7 times

Online Publication Date: 16 November 2006

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The InAsSbP/InAs light emitting diodes (LEDs) grown by liquid phase epitaxy and tuned at several wavelengths inside the 3–5 μm band were tested. Light pattern, radiation apparent temperature (Ta), thermal resistance, and self-heating details were characterized at T = 300 K in microscale by calibrated infrared cameras operating in the 3–5 and 8–12 μm bands. The authors show that LEDs dynamically simulate very hot (Ta ≥ 750 K) targets as well as cold objects and low observable. They resume that low cost LEDs enable a platform for photonic scene projection devices able to compete with thermal microemitter technology. Proposals on how to further increase LEDs performance are given.
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85.60.Jb Light-emitting devices
42.82.Bq Design and performance testing of integrated-optical systems
42.79.Kr Display devices, liquid-crystal devices

Photoluminescence and bowing parameters of InAsSb/InAs multiple quantum wells grown by molecular beam epitaxy

Po-Wei Liu, G. Tsai, H. H. Lin, A. Krier, Q. D. Zhuang, and M. Stone

Appl. Phys. Lett. 89, 201115 (2006); http://dx.doi.org/10.1063/1.2388879 (3 pages) | Cited 4 times

Online Publication Date: 17 November 2006

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Detailed studies are reported on the photoluminescence of InAsSb/InAs multiple quantum wells grown by molecular beam epitaxy on InAs substrates with the Sb mole fraction ranging from 0.06 to 0.13. From 4 K photoluminescence the band alignment was determined to be staggered type II. By comparing the emission peak energies with a transition energy calculation it was found that both the conduction and valence bands of InAsSb alloy exhibit some bowing. The bowing parameters were determined to be in the ratio of 4:6. For a sample with Sb composition ∼ 0.12 in the quantum well the photoluminescence emission band covers the CO2 absorption peak making it suitable for use in sources for CO2 detection.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.21.Fg Quantum wells

Sensitivity characteristics in nanosized coated long period gratings

Andrea Cusano, Agostino Iadicicco, Pierluigi Pilla, Antonello Cutolo, Michele Giordano, and Stefania Campopiano

Appl. Phys. Lett. 89, 201116 (2006); http://dx.doi.org/10.1063/1.2388885 (3 pages) | Cited 13 times

Online Publication Date: 17 November 2006

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This work presents an experimental analysis of the sensitivity characteristics to the surrounding refractive index (SRI) in long period gratings coated with polymeric overlay with high refractive index and thickness values ranging in hundreds of nanometers. The presence of the coating induces the cladding to overlay mode transition depending on the overlay features and the SRI. The immediate consequence is a drastic modification of the sensitivity characteristics from the sublinear monotone behavior to a resonantlike shape. Here, the sensitivity characteristics of coated long period gratings have been investigated to outline their dependence on the overlay thickness and order mode.
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42.81.Pa Sensors, gyros
42.79.Dj Gratings

High performance InP-based quantum cascade distributed feedback lasers with deeply etched lateral gratings

K. Kennedy, A. B. Krysa, J. S. Roberts, K. M. Groom, R. A. Hogg, D. G. Revin, L. R. Wilson, and J. W. Cockburn

Appl. Phys. Lett. 89, 201117 (2006); http://dx.doi.org/10.1063/1.2388887 (3 pages) | Cited 8 times

Online Publication Date: 17 November 2006

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The fabrication and operating characteristics of lateral grating distributed feedback InP-based quantum cascade lasers emitting at λ ∼ 10 μm are reported. High performance, room temperature single mode lasers, utilizing double-sided lateral gratings, are achieved in InP-based material grown by metal organic phase epitaxy. These deeply etched gratings are made possible by the development of a high aspect ratio, multistage, inductively coupled plasma etch process. A threshold current density of ∼ 5.5 kA/cm2 is measured at room temperature and side mode suppression ratio >20 dB with a tuning coefficient of −0.067 cm−1 K−1 is observed over a temperature range of 190–330 K.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Dj Gratings
81.65.Cf Surface cleaning, etching, patterning
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Photoluminescence oscillations in porous alumina films

K. Huang, L. Pu, Y. Shi, P. Han, R. Zhang, and Y. D. Zheng

Appl. Phys. Lett. 89, 201118 (2006); http://dx.doi.org/10.1063/1.2390645 (3 pages) | Cited 11 times

Online Publication Date: 17 November 2006

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The dominant oscillation shown in the laser-excited photoluminescence spectrum of the porous alumina film can be ascribed to the interference within a Fabry-Pérot optical cavity where the separation between two neighboring oscillations is highly sensitive to the film’s thickness and refractive index. The method, designated as photoluminescence oscillation, endows photoluminescence spectrum with another dimension and results in a nondestructive method for the measurement of the thickness and refractive index with a high resolution.
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78.66.Nk Insulators
78.55.Mb Porous materials
78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Broadband solid state optical amplifier based on a semiconducting polymer

D. Amarasinghe, A. Ruseckas, A. E. Vasdekis, M. Goossens, G. A. Turnbull, and I. D. W. Samuel

Appl. Phys. Lett. 89, 201119 (2006); http://dx.doi.org/10.1063/1.2390649 (3 pages) | Cited 15 times

Online Publication Date: 17 November 2006

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A compact, solid state optical amplifier based on the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] has been demonstrated. The amplifier was optically pumped. Gratings were used to couple the signal into and out of the film. The transmitted signal was amplified over 100 times in a 1 mm long waveguide giving 21 dB gain at 630 nm. A gain of >13 dB was observed at 615 and 650 nm giving a gain bandwidth of >26 THz. The gain dynamics at pump densities below 5 μJ/cm2 are described by an exciton-exciton annihilation model. At higher pump intensities, amplified spontaneous emission and photoinduced losses become significant.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.70.Jk Polymers and organics

Terahertz-wave near-field imaging with subwavelength resolution using surface-wave-assisted bow-tie aperture

Kunihiko Ishihara, Keishi Ohashi, Tomofumi Ikari, Hiroaki Minamide, Hiroyuki Yokoyama, Jun-ichi Shikata, and Hiromasa Ito

Appl. Phys. Lett. 89, 201120 (2006); http://dx.doi.org/10.1063/1.2387984 (3 pages) | Cited 24 times

Online Publication Date: 17 November 2006

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We demonstrate the terahertz-wave near-field imaging with subwavelength resolution using a bow-tie shaped aperture surrounded by concentric periodic structures in a metal film. A subwavelength aperture with concentric periodic grooves, which are known as a bull’s eye structure, shows extremely large enhanced transmission beyond the diffraction limit caused by the resonant excitation of surface waves. Additionally, a bow-tie aperture exhibits extraordinary field enhancement at the sharp tips of the metal, which enhances the transmission and the subwavelength spatial resolution. We introduced a bow-tie aperture to the bull’s eye structure and achieved high spatial resolution ( ∼ λ/17) in the near-field region. The terahertz-wave near-field image of the subwavelength metal pattern (pattern width = 20 μm) was obtained for the wavelength of 207 μm.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
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Monte Carlo simulation of high power microwave window breakdown at atmospheric conditions

John T. Krile, Andreas A. Neuber, Hermann G. Krompholz, and Thomas L. Gibson

Appl. Phys. Lett. 89, 201501 (2006); http://dx.doi.org/10.1063/1.2388877 (3 pages) | Cited 19 times

Online Publication Date: 14 November 2006

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A Monte Carlo-type electron motion simulation program was developed to calculate the increasing electron density for pulsed high power microwave window flashover in air and nitrogen at atmospheric pressures, i.e., >90 torr. Through comparison of experimental and simulated results several processes such as flashover delay time’s strong dependence on pressure and the lack of significant surface charge buildup have been confirmed. The quantitative agreement of the code results with the experiment is a clear step towards predicting high power microwave flashover under a wide range of atmospheric conditions as well as for different gases and more complex window geometries.
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52.80.Pi High-frequency and RF discharges
52.65.Pp Monte Carlo methods
52.25.Fi Transport properties

Method to determine argon metastable number density and plasma electron temperature from spectral emission originating from four 4p argon levels

Davide Mariotti, Yoshiki Shimizu, Takeshi Sasaki, and Naoto Koshizaki

Appl. Phys. Lett. 89, 201502 (2006); http://dx.doi.org/10.1063/1.2390631 (3 pages) | Cited 15 times

Online Publication Date: 15 November 2006

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A simple model and method is proposed here to determine argon metastable number densities and electron temperature with the assumption of a Maxwell-Boltzmann electron energy distribution. This method is based on the availability of experimental relative emission intensities of only four argon lines that originate from any of the 4p argon levels. The proposed model has a relatively wide range of validity for laboratory plasmas that contain argon gas and can be a valuable tool for the emerging field of atmospheric microplasmas, for which diagnostics is still limited.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Fi Transport properties
52.50.Dg Plasma sources
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
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Structural and electrical properties of low pressure metalorganic chemical vapor deposition grown Eu2O3 films on Si(100)

M. P. Singh, K. Shalini, S. A. Shivashankar, G. C. Deepak, and N. Bhat

Appl. Phys. Lett. 89, 201901 (2006); http://dx.doi.org/10.1063/1.2388128 (3 pages) | Cited 1 time

Online Publication Date: 13 November 2006

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Structural and electrical properties of Eu2O3 films grown on Si(100) in 500–600 °C temperature range by low pressure metalorganic chemical vapor deposition are reported. As-grown films also possess the impurity Eu1−xO phase, which has been removed upon annealing in O2 ambient. Film’s morphology comprises uniform spherical mounds (40–60 nm). Electrical properties of the films, as examined by capacitance-voltage measurements, exhibit fixed oxide charges in the range of −1.5×1011 to −6.0×1010 cm−2 and dielectric constant in the range of 8–23. Annealing has resulted in drastic improvement of their electrical properties. Effect of oxygen nonstoichiometry on the film’s property is briefly discussed.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ng Insulators
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
81.40.Gh Other heat and thermomechanical treatments

Oxygen-assisted control of surface morphology in nonepitaxial sputter growth of Ag

J. M. Riveiro, P. S. Normile, J. P. Andrés, J. A. González, J. A. De Toro, T. Muñoz, and P. Muñiz

Appl. Phys. Lett. 89, 201902 (2006); http://dx.doi.org/10.1063/1.2388140 (3 pages) | Cited 3 times

Online Publication Date: 14 November 2006

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The surface roughness of Ag films (thickness of 50 nm) is drastically reduced from 2.4 to 1.0 nm by the presence of oxygen (pressure of 2×10−5 mbar) during sputter growth, without a change (undermining) in electrical transport properties nor a formation of any Ag oxide phase. It is concluded that oxygen plays the role of a surfactant. The growth scenario (nonepitaxial sputter deposition of relatively thick films) makes this observation complementary to previous studies reporting surfactant effects in epitaxial growth of Ag. The authors consider an application of this finding in the field of multilayers involving Ag metals.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Cd Deposition by sputtering
73.61.At Metal and metallic alloys

Depth-resolved optical studies of excitonic and phonon-assisted transitions in ZnO epilayers

Yong-Hoon Cho, Ji-Young Kim, Ho-Sang Kwack, Bong-Joon Kwon, Le Si Dang, Hang-Ju Ko, and Takafumi Yao

Appl. Phys. Lett. 89, 201903 (2006); http://dx.doi.org/10.1063/1.2388252 (3 pages) | Cited 15 times

Online Publication Date: 14 November 2006

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The authors report depth-resolved optical properties of excitonic and phonon-assisted transitions in ZnO epilayers by photoluminescence (PL) and cathodoluminescence. A weaker free exciton (FX) emission than its first longitudinal optical phonon replica (FX-1LO) is observed at elevated temperatures (T>150 K) for interior area, while a stronger FX than FX-1LO is seen at all temperatures for top surface area of the sample. The authors exclude out a possible self-absorption process by PL excited at back surface of the sample. Therefore, the authors conclude that the different intensity ratios of FX and FX-1LO depending on the sample depth are strongly associated with extrinsic features of ZnO.
Show PACS
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.60.Hk Cathodoluminescence, ionoluminescence
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