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30 Mar 2009

Volume 94, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 133101 (2009); http://dx.doi.org/10.1063/1.3106057 (3 pages)

E. Sutter, D. P. Acharya, J. T. Sadowski, and P. Sutter
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Direct observation of two-step polarization reversal by an opposite field in a substrate-free piezoelectric thin sheet

Chun-Yi Hsieh, Yang-Fang Chen, Wan Y. Shih, Qing Zhu, and Wei-Heng Shih

Appl. Phys. Lett. 94, 131101 (2009); http://dx.doi.org/10.1063/1.3107264 (3 pages) | Cited 2 times

Online Publication Date: 31 March 2009

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The domain switching behavior of a substrate-free lead magnesium niobate-lead titanate thin sheet by an opposite electric field (E) was examined by piezoresponse force microscopy. It is shown that the polarization reversal process involved two steps. First, the polarization switched from the initial normal direction to an in-plane direction at −E<5 kV/cm. Second, at −E>5 kV/cm, the polarization was further switched from the in-plane direction to the opposite field direction. The preference of the in-plane polarization at −5 kV/cm was attributed to the thin-sheet geometry, which also manifested itself as a maximum in dielectric constant at the same field.
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77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
77.65.-j Piezoelectricity and electromechanical effects

Birefringent solid-core photonic bandgap fibers assisted by interstitial air holes

V. Pureur, G. Bouwmans, K. Delplace, Y. Quiquempois, and M. Douay

Appl. Phys. Lett. 94, 131102 (2009); http://dx.doi.org/10.1063/1.3104856 (3 pages) | Cited 3 times

Online Publication Date: 1 April 2009

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We report on the fabrication and the characterization of a design of highly birefringent solid-core photonic bandgap fibers. A form birefringence is obtained by keeping open all interstitial air holes but two diametrically opposite and close to the fiber core. Group birefringence as high as 0.57×10−3 and 0.47×10−3 at 1.1 and 1.55 μm, respectively, are demonstrated in the first bandgap.
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42.81.Wg Other fiber-optical devices
42.70.Qs Photonic bandgap materials
42.81.Bm Fabrication, cladding, and splicing
42.81.Gs Birefringence, polarization

High temperature cavity polaritons in epitaxial Er2O3 on silicon

C. P. Michael, V. A. Sabnis, H. B. Yuen, A. Jamora, S. Semans, P. B. Atanackovic, and O. Painter

Appl. Phys. Lett. 94, 131103 (2009); http://dx.doi.org/10.1063/1.3109791 (3 pages) | Cited 2 times

Online Publication Date: 1 April 2009

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Cavity polaritons around two Er3+ optical transitions are observed in microdisk resonators fabricated from epitaxial Er2O3 on Si(111). Using a pump-probe method, spectral anticrossings and linewidth averaging of the polariton modes are measured in the cavity transmission and luminescence at temperatures above 361 K.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Electrically pumped quantum post vertical cavity surface emitting lasers

Hyochul Kim, Matthew T. Rakher, Dirk Bouwmeester, and Pierre M. Petroff

Appl. Phys. Lett. 94, 131104 (2009); http://dx.doi.org/10.1063/1.3112578 (3 pages) | Cited 7 times

Online Publication Date: 1 April 2009

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We demonstrate low threshold electrically pumped lasing in oxide apertured vertical cavity surface emitting lasers with quantum posts (QPs) as the active medium. A lasing threshold current as low as 12 μA is achieved at 7 K and room temperature continuous wave lasing is also demonstrated in the cavities with quality factors of ∼ 10 000. At low temperature, the QP devices show remarkably lower lasing current thresholds compared to equivalent quantum dot devices.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

186 K operation of terahertz quantum-cascade lasers based on a diagonal design

Sushil Kumar, Qing Hu, and John L. Reno

Appl. Phys. Lett. 94, 131105 (2009); http://dx.doi.org/10.1063/1.3114418 (3 pages) | Cited 105 times

Online Publication Date: 1 April 2009

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Resonant-phonon terahertz quantum-cascade lasers operating up to a heat-sink temperature of 186 K are demonstrated. This record temperature performance is achieved based on a diagonal design, with the objective to increase the upper-state lifetime and therefore the gain at elevated temperatures. The increased diagonality also lowers the operating current densities by limiting the flow of parasitic leakage current. Quantitatively, the diagonality is characterized by a radiative oscillator strength that is smaller by a factor of two from the least of any previously published designs. At the lasing frequency of 3.9 THz, 63 mW of peak optical power was measured at 5 K, and approximately 5 mW could still be detected at 180 K.
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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

The effect of the internal capacitance of InGaN-light emitting diode on the electrostatic discharge properties

Soo-Kun Jeon, Jae-Gab Lee, Eun-Hyun Park, Jin Jang, Jae-Gu Lim, Seo-Kun Kim, and Joong-Seo Park

Appl. Phys. Lett. 94, 131106 (2009); http://dx.doi.org/10.1063/1.3114974 (2 pages) | Cited 15 times

Online Publication Date: 1 April 2009

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The electrostatic discharge (ESD) properties of the InGaN-light emitting diode (LED) were investigated in terms of the internal capacitance of the InGaN-LED. The LEDs with higher internal capacitance were found to be more resistant to external ESD impulses. The internal capacitance of the InGaN-LED was controlled by the silicon doping level of the n-GaN layer bordering the active layer. The human body model ESD yield at −500 V was increased from 27% to 94% by increasing the internal capacitance. Moreover, the high ESD pass yield was maintained up to −7000 V.
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85.60.Jb Light-emitting devices
61.72.uj III-V and II-VI semiconductors
81.05.Ea III-V semiconductors

A subwavelength near-infrared negative index material

Xuhuai Zhang, Marcelo Davanço, Yaroslav Urzhumov, Gennady Shvets, and Stephen R. Forrest

Appl. Phys. Lett. 94, 131107 (2009); http://dx.doi.org/10.1063/1.3110957 (3 pages) | Cited 3 times

Online Publication Date: 2 April 2009

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A single layer of a subwavelength negative index material (NIM) operating at a wavelength of 1 μm is demonstrated. The geometrical parameters of the nanostructure are determined by characterizing its optical transmission spectrum. We show through photonic band calculations that these parameters give rise to a negative index in a corresponding bulk NIM. The fabrication inaccuracies in the dielectric spacer thickness that are likely to be introduced in a prism composed of multiple layers of this structure are shown through full-wave simulations to be within a range that preserves its negative refractive behavior.
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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)
42.79.Wc Optical coatings
42.79.Bh Lenses, prisms and mirrors

Circularly polarized lasing in a (110)-oriented quantum well vertical-cavity surface-emitting laser under optical spin injection

Hiroshi Fujino, Shinji Koh, Satoshi Iba, Toshiyasu Fujimoto, and Hitoshi Kawaguchi

Appl. Phys. Lett. 94, 131108 (2009); http://dx.doi.org/10.1063/1.3112576 (3 pages) | Cited 13 times

Online Publication Date: 2 April 2009

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We fabricated and characterized a vertical-cavity surface-emitting laser (VCSEL) based on (110) InGaAs/GaAs multiple quantum wells (MQWs). Circularly polarized lasing in the (110) VCSEL by optical injection of spin-polarized electrons has been demonstrated at 77 K and room temperature. A high degree of circular polarization, 0.94, was observed at 77 K, reflecting the long electron spin relaxation time in the (110) MQWs.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Wavelength agile superlattice quantum dot infrared photodetector

G. Ariyawansa, A. G. U. Perera, G. Huang, and P. Bhattacharya

Appl. Phys. Lett. 94, 131109 (2009); http://dx.doi.org/10.1063/1.3114420 (3 pages) | Cited 9 times

Online Publication Date: 3 April 2009

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A dual-band superlattice quantum dot infrared photodetector, providing bias-selectability of the response peaks, is demonstrated. The active region consists of two quantum dot superlattices separated by a graded barrier, enabling photocurrent generation only in one superlattice for a given bias polarity. Two response bands, one consisting of three peaks at 2.9, 3.2, and 4.9 μm and the other consisting of three peaks at 4.4, 7.4, and 11 μm, were observed up to 120 K for reverse and forward biases, respectively. The specific detectivity values at 80 K are 3.2 and 2.6×109 Jones for the 4.9 and 7.4 μm peaks.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Tapered fiber Mach–Zehnder interferometer for simultaneous measurement of refractive index and temperature

Ping Lu, Liqiu Men, Kevin Sooley, and Qiying Chen

Appl. Phys. Lett. 94, 131110 (2009); http://dx.doi.org/10.1063/1.3115029 (3 pages) | Cited 45 times

Online Publication Date: 3 April 2009

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An approach to achieve simultaneous measurement of refractive index and temperature is proposed by using a Mach–Zehnder interferometer realized on tapered single-mode optical fiber. The attenuation peak wavelength of the interference with specific order in the transmission spectrum shifts with changes in the environmental refractive index and temperature. By utilizing S-band and C/L-band light sources, simultaneous discrimination of refractive index and temperature with the tapered fiber Mach–Zehnder interferometer is demonstrated with the corresponding sensitivities of −23.188 nm/RIU (refractive index unit) and 0.071 nm/ °C, and −26.087 nm/RIU (blueshift) and 0.077 nm/°C (redshift) for the interference orders of 169 and 144, respectively.
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07.60.Ly Interferometers
42.81.Pa Sensors, gyros
07.60.Vg Fiber-optic instruments
07.60.Hv Refractometers and reflectometers
07.20.Dt Thermometers
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Self-excited nonlinear plasma series resonance oscillations in geometrically symmetric capacitively coupled radio frequency discharges

Z. Donkó, J. Schulze, U. Czarnetzki, and D. Luggenhölscher

Appl. Phys. Lett. 94, 131501 (2009); http://dx.doi.org/10.1063/1.3110056 (3 pages) | Cited 23 times

Online Publication Date: 1 April 2009

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At low pressures, nonlinear self-excited plasma series resonance (PSR) oscillations are known to drastically enhance electron heating in geometrically asymmetric capacitively coupled radio frequency discharges by nonlinear electron resonance heating (NERH). Here we demonstrate via particle-in-cell simulations that high-frequency PSR oscillations can also be excited in geometrically symmetric discharges if the driving voltage waveform makes the discharge electrically asymmetric. This can be achieved by a dual-frequency (f+2f) excitation, when PSR oscillations and NERH are turned on and off depending on the electrical discharge asymmetry, controlled by the phase difference of the driving frequencies.
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52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.65.-y Plasma simulation
52.80.-s Electric discharges
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
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Planar metamaterial with transmission and reflection that depend on the direction of incidence

E. Plum, V. A. Fedotov, and N. I. Zheludev

Appl. Phys. Lett. 94, 131901 (2009); http://dx.doi.org/10.1063/1.3109780 (3 pages) | Cited 13 times

Online Publication Date: 30 March 2009

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We report that normal incidence reflection and transmission of circularly polarized electromagnetic waves from and through planar split-ring microwave metamaterials with chiral symmetry breaking depends on the incidence direction and handedness of circular polarization. The effect has a resonant nature and is linked to the lack of mirror symmetry in the metamaterial pattern leading to a polarization-sensitive excitation of electric and magnetic dipolar responses in the meta-molecules. It has striking phenomenological resemblance with the reflective circular dichroism of high-temperature “anyon” superconductors.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
41.20.Jb Electromagnetic wave propagation; radiowave propagation

Size-induced elastic stiffening of ZnO nanostructures: Skin-depth energy pinning

X. J. Liu, J. W. Li, Z. F. Zhou, L. W. Yang, Z. S. Ma, G. F. Xie, Y. Pan, and Chang Q. Sun

Appl. Phys. Lett. 94, 131902 (2009); http://dx.doi.org/10.1063/1.3109786 (3 pages) | Cited 24 times

Online Publication Date: 30 March 2009

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It has long been puzzling regarding the trends and physical origins of the size-effect on the elasticity of ZnO nanostructures. An extension of the atomic “coordination-radius” correlation premise of Pauling and Goldschmidt to energy domain has enabled us to clarify that the elastic modulus is intrinsically proportional to the sum of bond energy per unit volume and that the size-induced elastic stiffening arises from (i) the broken-bond-induced local strain and skin-depth energy pinning and (ii) the tunable fraction of bonds between the undercoordinated atoms, and therefore, the elastic modulus of ZnO nanostructures should increase with the inverse of feature size.
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62.25.-g Mechanical properties of nanoscale systems
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli

Magnetic properties of some metastable Co–Ru alloys studied by ion beam mixing and ab initio calculation

W. C. Wang, Y. Dai, T. L. Wang, J. H. Li, X. He, and B. X. Liu

Appl. Phys. Lett. 94, 131903 (2009); http://dx.doi.org/10.1063/1.3109796 (3 pages) | Cited 1 time

Online Publication Date: 30 March 2009

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Magnetic fcc-Co75Ru25 (L12) phase and nonmagnetic fcc-Co25Ru75 (L12) phase are obtained by ion beam mixing in the respective Co–Ru multilayered films. Interestingly, in the Co50Ru50 multilayered films, a magnetic dual-fcc phase, identified to be a mixture consisting of a magnetic fcc-Co75Ru25 and a nonmagnetic fcc-Co25Ru75 phases, is observed at an irradiation dose of 3×1015 Xe+/cm2 and, upon further irradiation to a dose of 7×1015 Xe+/cm2, transformed into a nonmagnetic single-fcc phase with an alloy composition back to be Co50Ru50.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
61.80.Jh Ion radiation effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Zero thermal expansion in a pure-form antiperovskite manganese nitride

K. Takenaka and H. Takagi

Appl. Phys. Lett. 94, 131904 (2009); http://dx.doi.org/10.1063/1.3110046 (3 pages) | Cited 27 times

Online Publication Date: 30 March 2009

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A zero thermal expansion material in a pure form is fabricated using an antiperovskite manganese nitride. The isotropic zero thermal expansion is achieved by optimizing the heat treatment and the chemical composition. The present study suggests that the heat treatment affects the thermal expansion mainly via the nitrogen content of the material. The obtained materials exhibit a low expansion of |α|<0.5×10−6 K−1 (α is the coefficient of linear thermal expansion) over a broad temperature range, which includes room temperature. They are desirable for many fields of industry as reliable, mechanically hard, and low-cost zero thermal expansion materials.
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65.40.De Thermal expansion; thermomechanical effects
81.40.Gh Other heat and thermomechanical treatments
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Accurate determination of subnanoscale deformation with combined laser calorimetry and surface thermal lens technique

Mingqiang Liu, Bincheng Li, and Yanru Wang

Appl. Phys. Lett. 94, 131905 (2009); http://dx.doi.org/10.1063/1.3106630 (3 pages) | Cited 1 time

Online Publication Date: 31 March 2009

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Laser-induced surface deformations of optical components are measured with a combined laser calorimetry (LC) and surface thermal lens (STL) technique. The deformation is calculated from the STL amplitude by employing a simple STL model. It is also directly calculated with a rigorous deformation model by measuring the absorptance of the optical component with LC. Experimentally, the laser-induced surface deformation values of a BK7 coating sample measured by STL and Hartmann wavefront sensing techniques are in excellent agreement with that calculated with the rigorous deformation model. The measurement of subnanometer deformation with the combined LC and STL technique is demonstrated by a fused silica coating sample. The deformation measurement sensitivity and error are estimated to be 10 pm and below 10%, respectively.
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42.87.-d Optical testing techniques
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
42.79.Wc Optical coatings
07.20.Fw Calorimeters

Nanoscale wavy fracture surface of a Pd-based bulk metallic glass

N. Chen, D. V. Louzguine-Luzgin, G. Q. Xie, and A. Inoue

Appl. Phys. Lett. 94, 131906 (2009); http://dx.doi.org/10.1063/1.3109797 (3 pages) | Cited 1 time

Online Publication Date: 31 March 2009

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The authors report the observations of nanoscale wavy steps on fracture surface of a Pd-based bulk metallic glass. The wavy steps are generated by crack front waves. Besides this kind of steps, it is also found that there is a dispersive microscale wavy trace aligned along a backbone “branch line,” which is induced by dynamic instability of a rapidly propagating crack front. Such microbranching events are evidenced as dissipating energy accumulated at the crack front by creating the additional fracture surface area when the crack propagation exceeds a critical velocity.
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81.05.Kf Glasses (including metallic glasses)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mm Fracture
62.20.mt Cracks

Edge-enhanced Raman scattering in Si nanostripes

Vladimir Poborchii, Tetsuya Tada, and Toshihiko Kanayama

Appl. Phys. Lett. 94, 131907 (2009); http://dx.doi.org/10.1063/1.3110964 (3 pages) | Cited 8 times

Online Publication Date: 31 March 2009

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We show both theoretically and experimentally that at the 364 nm excitation wavelength, the Raman signal is strongly enhanced within a local (<20 nm wide) area at the Si stripe edge when both incident and scattered lights are polarized parallel to the stripe. This enhancement effect results from a high concentration of the light electric field at the stripe edge and allows single nanowire Raman measurement as well as local stress detection at the stripe edges in Si device structures.
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78.30.Am Elemental semiconductors and insulators
78.20.Jq Electro-optical effects
62.23.-c Structural classes of nanoscale systems
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Characterizing nanometer-sized V-defects in InGaN single quantum well films by high-spatial-resolution cathodoluminescence spectroscopy

M. Yoshikawa, M. Murakami, H. Ishida, and H. Harima

Appl. Phys. Lett. 94, 131908 (2009); http://dx.doi.org/10.1063/1.3104850 (3 pages) | Cited 10 times

Online Publication Date: 1 April 2009

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We studied cathodoluminescence (CL) spectral variations in the vicinity of the V-defects in InGaN single quantum well (SQW) films by using our newly developed SE-SEM-CL. The peak intensity and peak wavelength of the CL peaks around 448 and 400 nm were found to change significantly near the apex of a V-defect. These variations were mainly attributed to a change in the In content of the InGaN SQW layer in the sidewalls and apex of the V-defect. Furthermore, an abnormal change was observed in the CL peak at 365 nm near the apex of the V-defect; this change was mainly caused by the stress induced by a force at the film edge that results from the thermal expansion differences between the film and the GaN layer. On the basis of the obtained results, we proposed a model of the formation of V-defects by selective termination of the threading defects on the (0001) surface of pseudomorphic InGaN SQW and GaN buffer layers by In.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
68.65.Fg Quantum wells
65.40.De Thermal expansion; thermomechanical effects
78.67.De Quantum wells

Elastic and adhesive properties of alkanethiol self-assembled monolayers on gold

Frank W. DelRio, Cherno Jaye, Daniel A. Fischer, and Robert F. Cook

Appl. Phys. Lett. 94, 131909 (2009); http://dx.doi.org/10.1063/1.3111440 (3 pages) | Cited 17 times

Online Publication Date: 1 April 2009

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Elastic and adhesive properties of alkanethiol [CH3(CH2)n−1SH] self-assembled monolayers on gold are investigated by atomic force microscopy and correlated with surface structure via near edge x-ray absorption fine structure spectroscopy. As the chain length n decreases from 18 to 5, the elastic modulus of the monolayer film, Efilm, decreases from 1.0 to 0.15 GPa and the work of adhesion, w, increases from 82.8 to 168.3 mJ m−2. The Efilm and w trends are interpreted in terms of the dichroic ratios, RI, which reveal distinct changes in chain orientation, order, and coverage over the range of n.
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68.37.Ps Atomic force microscopy (AFM)
68.35.Np Adhesion
78.70.Dm X-ray absorption spectra
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces

Room-temperature dislocation climb in metallic interfaces

Jian Wang, Richard G. Hoagland, and Amit Misra

Appl. Phys. Lett. 94, 131910 (2009); http://dx.doi.org/10.1063/1.3111137 (3 pages) | Cited 14 times

Online Publication Date: 1 April 2009

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Using atomistic simulations, we show that dislocations efficiently climb in metallic interfaces, such as Cu–Nb, through absorption and emission of vacancies and a counter diffusion of Cu atoms in the interfacial plane. The efficiency of dislocation climb is ascribed to the high vacancy concentration of 0.05 in the interfacial plane, the low formation energy of 0.12 eV with respect to removal or insertion of Cu atoms, and the low kinetic barrier of 0.10 eV for vacancy migration. Dislocation climb facilitates reactions of interfacial dislocations and enables interfaces to be in the equilibrium state with respect to concentrations of point defects.
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68.35.Ct Interface structure and roughness
61.72.Bb Theories and models of crystal defects
61.72.jd Vacancies

X-ray measurements of the strain and shape of dielectric/metallic wrap-gated InAs nanowires

J. Eymery, V. Favre-Nicolin, L. Fröberg, and L. Samuelson

Appl. Phys. Lett. 94, 131911 (2009); http://dx.doi.org/10.1063/1.3114369 (3 pages) | Cited 4 times

Online Publication Date: 1 April 2009

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Wrap-gate (111) InAs nanowires (NWs) were studied after HfO2 dielectric coating and Cr metallic deposition by a combination of grazing incidence x-ray techniques. In-plane and out-of-plane x-ray diffraction (crystal truncation rod analysis) allow determining the strain tensor. The longitudinal contraction, increasing with HfO2 and Cr deposition, is significantly larger than the radial dilatation. For the Cr coating, the contraction along the growth axis is quite large (−0.95%), and the longitudinal/radial deformation ratio is >10, which may play a role on the NW transport properties. Small angle x-ray scattering shows a smoothening of the initial hexagonal bare InAs NW shape and gives the respective core/shell thicknesses, which are compared to flat surface values.
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73.63.Nm Quantum wires
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
81.40.Lm Deformation, plasticity, and creep
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Photoluminescence dynamics in GaAs/AlAs quantum wells modulated by one-dimensional standing surface acoustic waves

Tetsuomi Sogawa, Haruki Sanada, Hideki Gotoh, Hiroshi Yamaguchi, Sen Miyashita, and Paulo V. Santos

Appl. Phys. Lett. 94, 131912 (2009); http://dx.doi.org/10.1063/1.3114382 (3 pages) | Cited 4 times

Online Publication Date: 1 April 2009

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The effects of standing surface acoustic waves (SAWs) on carrier dynamics in GaAs/AlAs quantum wells are investigated by spatially and time-resolved photoluminescence (PL) spectroscopy. We found that the PL spectra vary considerably depending on the position and the phase of the standing SAW field. The PL spectra are characterized by oscillations in the PL intensity and emission energy due to the motion of free carriers and excitons driven by the piezoelectric fields as well as by the strain-induced band-gap gradient. It is also demonstrated that the positions of the nodes and antinodes of the standing SAW are precisely controlled.
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78.55.Cr III-V semiconductors
78.67.De Quantum wells
73.21.Fg Quantum wells
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
71.35.-y Excitons and related phenomena
78.47.jd Time resolved luminescence
68.35.Iv Acoustical properties
73.63.Hs Quantum wells
72.20.Dp General theory, scattering mechanisms

Determination of the room temperature thermal conductivity of RuO2 by the photothermal deflection technique

Dino Ferizović, Lindsay K. Hussey, Ying-Sheng Huang, and Martin Muñoz

Appl. Phys. Lett. 94, 131913 (2009); http://dx.doi.org/10.1063/1.3115030 (3 pages) | Cited 3 times

Online Publication Date: 3 April 2009

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A thermal conductivity study of RuO2 single crystals has been carried out via the photothermal deflection technique in transverse configuration at room temperature. The thermal diffusivity and conductivity of RuO2 crystals are determined to be 0.17 cm2 s−1 and 0.50 W cm−1 K−1, respectively. Furthermore, it was found that the thermal conductivity has inversely proportional temperature dependence in the region between 50 and 300 K.
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66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
66.30.Xj Thermal diffusivity
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
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Surface passivation and interface reactions induced by hydrogen peroxide treatment of n-type ZnO (000math)

R. Schifano, E. V. Monakhov, B. G. Svensson, and S. Diplas

Appl. Phys. Lett. 94, 132101 (2009); http://dx.doi.org/10.1063/1.3106052 (3 pages) | Cited 10 times

Online Publication Date: 1 April 2009

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X-ray photoemission spectroscopy and electrical measurements have been employed to study O-face (000math) n-type ZnO samples treated by hydrogen peroxide (H2O2). A highly resistive and oxygen-rich surface layer is revealed, presumably caused by a high concentration of zinc vacancies and/or adsorbed O2 molecules. As a result, the surface exhibits upward energy band bending ( ∼ 0.4 eV) promoting the formation of high barrier Schottky contacts and suppressing the surface leakage current. Furthermore, after Pd deposition an enhanced formation of PdO is found at the Pd/ZnO interface for the H2O2-treated samples, and this is also expected to increase the resulting Schottky barrier height ( ∼ 0.6 eV), which yields up to seven orders of magnitude in current rectification between forward and reverse bias voltage.
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81.65.Rv Passivation
73.30.+y Surface double layers, Schottky barriers, and work functions
61.72.jd Vacancies
68.43.Mn Adsorption kinetics
72.80.Ey III-V and II-VI semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
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