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24 Dec 2012

Volume 101, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 263501 (2012); http://dx.doi.org/10.1063/1.4772532 (4 pages)

Youngki Yoon and Sayeef Salahuddin
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Electrically controlled absorption in a slab waveguide formed by the implantation of protons in a potassium lithium tantalate niobate substrate

Har'el Ilan and Aharon J. Agranat

Appl. Phys. Lett. 101, 261101 (2012); http://dx.doi.org/10.1063/1.4772987 (4 pages)

Online Publication Date: 26 December 2012

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Electrically controlled absorption was observed in a slab waveguide, fabricated in a potassium lithium tantalate niobate substrate by proton implantation, at an energy of E = 1.15 MeV and a fluence of 6.1×1016ions/cm2. The implantation created an amorphous layer which acted as the cladding with an adjacent proton doped layer at its bottom. It is suggested that a n-i junction is formed at the interface between the proton layer and the substrate, which is the core of the waveguide. The electrically controlled absorption is attributed to changes in the width of the depletion area of the n-i junction induced by the applied field.
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42.79.Gn Optical waveguides and couplers
42.82.Cr Fabrication techniques; lithography, pattern transfer
61.43.-j Disordered solids
61.72.U- Doping and impurity implantation
42.65.Wi Nonlinear waveguides

Enhanced photocurrent in crystalline silicon solar cells by hybrid plasmonic antireflection coatings

Narges F. Fahim, Zi Ouyang, Baohua Jia, Yinan Zhang, Zhengrong Shi, and Min Gu

Appl. Phys. Lett. 101, 261102 (2012); http://dx.doi.org/10.1063/1.4773038 (5 pages)

Online Publication Date: 26 December 2012

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Photocurrent enhancement induced by plasmonic light trapping is of great interest for photovoltaics. We design and demonstrate hybrid plasmonic antireflection coatings as an efficient light trapping strategy for broadband absorption and photocurrent enhancement in crystalline silicon solar cells. Gold nanoparticles of size ranging from 15 to 150 nm are embedded in standard SiNx antireflection coatings with a thickness of 90 nm. Through optimizing the location of tailored nanoparticles within the SiNx layer, both light scattering enhancement and near-field light concentration can be harnessed. A maximum increase of 6.3% in photocurrent is achieved for textured multi-crystalline Si solar cells with the optimum configuration.
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88.40.jj Silicon solar cells
42.79.Wc Optical coatings
88.40.hj Efficiency and performance of solar cells

Broadband and tunable mid-infrared laser source based on a transversal array of chirped filaments

J.-F. Daigle, F. Théberge, G. Roy, M. Châteauneuf, and J. Dubois

Appl. Phys. Lett. 101, 261103 (2012); http://dx.doi.org/10.1063/1.4773246 (3 pages)

Online Publication Date: 26 December 2012

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A scheme for the generation of broadband and tunable mid-infrared pulses based on two-color filamentation in air is presented. The mid-infrared pulses, spanning the spectral region between 4 and 6.5 μm, result from a third-order nonlinear interaction between two short pulses, one at 800 nm and the other at 437 nm. The latter was created by frequency doubling a Raman-shifted pulse at 873 nm amplified in a chirped-pulse Raman amplifier. Tunability of this mid-infrared laser source was provided by introducing spatial chirp across the fundamental pulse profile which created a transversal array of chirped filaments.
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42.60.Fc Modulation, tuning, and mode locking
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Effect of spatial coherence on determining the topological charge of a vortex beam

Chengliang Zhao, Fei Wang, Yuan Dong, Yujing Han, and Yangjian Cai

Appl. Phys. Lett. 101, 261104 (2012); http://dx.doi.org/10.1063/1.4773236 (5 pages)

Online Publication Date: 26 December 2012

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It is known that one can determine the topological charge of a vortex beam based on the Fourier transform of its intensity. We demonstrate both theoretically and experimentally that this method will be invalid for determining the topological charge of a vortex beam with low coherence. Furthermore, we propose a method to determine the topological charge of a vortex beam with low coherence based on its complex degree of coherence.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Effect of the counter cation on the third order nonlinearity in anionic Au dithiolene complexes

K. Iliopoulos, A. El-Ghayoury, B. Derkowska, A. Ranganathan, P. Batail, D. Gindre, and B. Sahraoui

Appl. Phys. Lett. 101, 261105 (2012); http://dx.doi.org/10.1063/1.4772476 (4 pages) | Cited 1 time

Online Publication Date: 27 December 2012

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In this work, we present the third order nonlinear optical investigation of two gold complexes, which differ by the nature of the counter cations. The impact of the different design in the architecture through a set of hydrogen bonds in the case of Au-Mel of the systems on the nonlinearity has been studied by means of the Z-scan setup under 532 nm, 30 ps laser excitation, allowing for the determination of the nonlinear absorption and refraction of the samples. Significant modification of the nonlinear optical response between the two metal complexes has been found suggesting a clear effect of the counter cation.
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42.65.An Optical susceptibility, hyperpolarizability
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.Jk Polymers and organics
61.66.Hq Organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.47.J- Ultrafast spectroscopy (<1 psec)

p-InGaN/AlGaN electron blocking layer for InGaN/GaN blue light-emitting diodes

Zhiqiang Liu, Jun Ma, Xiaoyan Yi, Enqing Guo, Liancheng Wang, Junxi Wang, Na Lu, Jinmin Li, Ian Ferguson, and Andrew Melton

Appl. Phys. Lett. 101, 261106 (2012); http://dx.doi.org/10.1063/1.4773187 (4 pages)

Online Publication Date: 27 December 2012

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In this work, the advantages of the p-InGaN/AlGaN electron blocking layer (EBL) for InGaN/GaN light-emitting diodes (LEDs) were studied numerically and experimentally. The LEDs with p-InGaN/AlGaN EBL exhibited better optical performance over a wide range of carrier concentration due to the enhancement of holes' injection and electrons' confinement. The values of A, B, C, and D coefficients had been iteratively obtained by fitting quantum efficiency in the modified rate equation model. The analysis indicated that the improvement in the device properties could be attributed to the relatively small band gap and p-type doping of InGaN insertion layer.
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85.60.Jb Light-emitting devices
02.60.-x Numerical approximation and analysis

Superradiant Raman laser magnetometer

Joshua M. Weiner, Kevin C. Cox, Justin G. Bohnet, Zilong Chen, and James K. Thompson

Appl. Phys. Lett. 101, 261107 (2012); http://dx.doi.org/10.1063/1.4773241 (4 pages)

Online Publication Date: 27 December 2012

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We demonstrate a proof-of-principle magnetometer that relies on the active oscillation of a cold atom Raman laser to continuously map a field-sensitive atomic phase onto the phase of the radiated light. We demonstrate wideband sensitivity during continuous active oscillation, as well as narrowband sensitivity in passive Ramsey-like mode with translation of the narrowband detection in frequency using spin-echo techniques. The sensor operates with a sensitivity of 190 pT/math at 1 kHz and effective sensing volume of 2×10−3 mm3. Fundamental quantum limits on the magnetic field sensitivity of an ideal detector are also considered.
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07.55.Ge Magnetometers for magnetic field measurements

High sensitivity and fast response and recovery times in a ZnO nanorod array/p-Si self-powered ultraviolet detector

J. J. Hassan, M. A. Mahdi, S. J. Kasim, Naser M. Ahmed, H. Abu Hassan, and Z. Hassan

Appl. Phys. Lett. 101, 261108 (2012); http://dx.doi.org/10.1063/1.4773245 (3 pages) | Cited 3 times

Online Publication Date: 27 December 2012

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High quality, vertically aligned ZnO nanorods were grown on a silicon substrate, using microwave-assisted chemical bath deposition with poly (vinyl alcohol)-Zn(OH)2 nanocomposites as seed layer. The structure and surface morphology of the prepared ZnO nanorod arrays were characterized using X-ray diffraction and scanning electron microscopy. The optical properties were assessed using photoluminescence measurements; the results showed a high-intensity UV peak, and a lower intensity, broader visible peak. Upon exposure to 395 nm light at a zero-bias voltage, the UV detector showed a high sensitivity of 8000% and fast response and recovery times of 25 and 22 ms, respectively.
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81.16.-c Methods of micro- and nanofabrication and processing
85.60.Gz Photodetectors (including infrared and CCD detectors)
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)
78.67.Qa Nanorods
78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors

Germanium metal-semiconductor-metal photodetectors evanescently coupled with upper-level silicon oxynitride dielectric waveguides

Juan C. Cervantes-González, Donghwan Ahn, Xiaoguang Zheng, Sanjay K. Banerjee, Alfonso T. Jacome, Joe C. Campbell, and Ignacio E. Zaldivar-Huerta

Appl. Phys. Lett. 101, 261109 (2012); http://dx.doi.org/10.1063/1.4773212 (3 pages)

Online Publication Date: 28 December 2012

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We demonstrate Ge-on-Si metal-semiconductor-metal (MSM) photodetectors monolithically integrated with silicon oxynitride (SiOxNy) waveguides. The waveguide is placed on top of the photodetector and between the metal electrodes, evading the shading effect by metal electrodes, which is typical in surface-illuminated MSM photodetectors. The devices showed responsivity of about 0.45 A/W for 80 μm long devices at 1550 nm. The photodetector with 1.5 μm electrode spacing showed 3 dB bandwidth of 2.0 GHz at −2 V and 2 μA dark current. Further studies suggest that with a modified design the structure is capable of achieving 1 A/W responsivity and greater bandwidth.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
84.40.Az Waveguides, transmission lines, striplines

Development of polystyrene-based scintillation materials and its mechanisms

Hidehito Nakamura, Hisashi Kitamura, Osamu Shinji, Katashi Saito, Yoshiyuki Shirakawa, and Sentaro Takahashi

Appl. Phys. Lett. 101, 261110 (2012); http://dx.doi.org/10.1063/1.4773298 (3 pages)

Online Publication Date: 28 December 2012

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Scintillation materials based on polystyrene (PS) have been investigated. Para-terphenyl was employed as a fluorescent molecule (fluor) that functions as a wavelength shifter. A clear increase in photon yield of the scintillation materials relative to the pure PS was observed, which cannot be explained by the conventional theory of scintillation mechanism. Furthermore, the photon yield increased with flour concentration in accordance with a power-law. Here we reveal the emergence of a luminescence of PS-based scintillation materials and demonstrate that their photon yields can be controlled by the fluor concentration.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.70.Ps Scintillation
78.55.Kz Solid organic materials

An all-fiber source of pulsed twin beams for quantum communication

Xueshi Guo, Xiaoying Li, Nannan Liu, Lei Yang, and Z. Y. Ou

Appl. Phys. Lett. 101, 261111 (2012); http://dx.doi.org/10.1063/1.4773303 (5 pages)

Online Publication Date: 28 December 2012

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Motivated by the pursuit of a simple system to produce a continuous variable non-classical light source for long-distance quantum communication, we construct an all-fiber source of pulsed twin beams in the 1550 nm band by using a high gain fiber optical parametric amplifier. The intensity-difference noise of the twin beams is below the shot noise limit by 3.1 dB (10.4 dB after correction for losses). A detailed study reveals a number of limiting factors for noise reduction. Therefore, further noise reduction will be feasible once care is taken for these limiting factors.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Mi Dynamical laser instabilities; noisy laser behavior
42.65.Yj Optical parametric oscillators and amplifiers
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
03.67.Hk Quantum communication
05.40.Ca Noise
42.50.Lc Quantum fluctuations, quantum noise, and quantum jumps

High responsivity of amorphous indium gallium zinc oxide phototransistor with Ta2O5 gate dielectric

T. H. Chang, C. J. Chiu, W. Y. Weng, S. J. Chang, T. Y. Tsai, and Z. D. Huang

Appl. Phys. Lett. 101, 261112 (2012); http://dx.doi.org/10.1063/1.4773307 (3 pages)

Online Publication Date: 28 December 2012

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This study investigates the electrical performance of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with a Ta2O5 gate dielectric under monochromatic illumination. The relationship between the phototransistor performance and oxygen partial pressure is determined. The oxygen content of the a-IGZO channel significantly affects the electrical and optical characteristics of a-IGZO TFTs. At applied gate biases of 0, 0, and 0.25 V, oxygen partial pressures of 0%, 0.1%, and 0.2% yielded measured device responsivities of 0.23, 0.44, and 4.75 A/W, respectively. Oxygen content can be used to control the mobility of TFTs, which can amplify photocurrent and enhance the responsivity of a-IGZO TFTs with a Ta2O5 gate dielectric.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Tv Field effect devices

Room-temperature transverse-electric polarized intersubband electroluminescence from InAs/AlInAs quantum dashes

V. Liverini, L. Nevou, F. Castellano, A. Bismuto, M. Beck, Fabian Gramm, and J. Faist

Appl. Phys. Lett. 101, 261113 (2012); http://dx.doi.org/10.1063/1.4773360 (5 pages) | Cited 1 time

Online Publication Date: 28 December 2012

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We report the observation of transverse electric polarized electroluminescence from InAs/AlInAs quantum dash quantum cascade structures up to room temperature. The emission is attributed to the electric field confined along the shortest lateral dimension of the dashes, as confirmed by its dependence on crystallographic orientation both in absorption measurements on a dedicated sample and from electroluminescence itself. From the absorption, we estimate a dipole moment for the observed transition of 〈x〉 = 1.7 nm. The electroluminescence is peaked at around 110 meV and increases with applied bias. Its temperature dependence shows a decrease at higher temperatures limited by optical phonon emission.
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81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.60.Fi Electroluminescence

A multicolor, broadband (5–20 μm), quaternary-capped InAs/GaAs quantum dot infrared photodetector

Sourav Adhikary, Yigit Aytac, Srujan Meesala, Seyoum Wolde, A. G. Unil Perera, and Subhananda Chakrabarti

Appl. Phys. Lett. 101, 261114 (2012); http://dx.doi.org/10.1063/1.4773373 (4 pages) | Cited 2 times

Online Publication Date: 28 December 2012

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An InAs/GaAs quantum dot infrared photodetector with strong, multicolor, broadband (5–20 μm) photoresponse is reported. Using a combined quaternary In0.21Al0.21Ga0.58As and GaAs capping that relieves strain and maintains strong carrier confinement, we demonstrate a four color infrared response with peaks in the midwave- (5.7 μm), longwave- (9.0 and 14.5 μm), and far- (17 μm) infrared regions. Narrow spectral widths (7% to 9%) are noted at each of these wavelengths including responsivity value ∼95.3 mA/W at 14.5 μm. Using strain field and multi-band k⋅p theory, we map specific bound-to-bound and bound-to-quasibound transitions to the longwave and midwave responses, respectively.
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78.67.Hc Quantum dots
85.60.Gz Photodetectors (including infrared and CCD detectors)

Efficient terahertz electro-absorption modulation employing graphene plasmonic structures

Berardi Sensale-Rodriguez, Rusen Yan, Mingda Zhu, Debdeep Jena, Lei Liu, and Huili Grace Xing

Appl. Phys. Lett. 101, 261115 (2012); http://dx.doi.org/10.1063/1.4773374 (3 pages) | Cited 2 times

Online Publication Date: 28 December 2012

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We propose and discuss terahertz (THz) electro-absorption modulators based on graphene plasmonic structures. The active device consists of a self-gated pair of graphene layers, which are patterned to structures supporting THz plasmonic resonances. These structures allow for efficient control of the effective THz optical conductivity, thus absorption, even at frequencies much higher than the Drude roll-off in graphene where most previously proposed graphene-based devices become inefficient. Our analysis shows that reflectance-based device configurations, engineered so that the electric field is enhanced in the active graphene pair, could achieve very high modulation-depth, even ∼100%, over a wide frequency range up to tens of THz.
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42.79.Hp Optical processors, correlators, and modulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Jq Electro-optical effects

Dynamics of a polariton condensate transistor switch

C. Antón, T. C. H. Liew, G. Tosi, M. D. Martín, T. Gao, Z. Hatzopoulos, P. S. Eldridge, P. G. Savvidis, and L. Viña

Appl. Phys. Lett. 101, 261116 (2012); http://dx.doi.org/10.1063/1.4773376 (4 pages)

Online Publication Date: 28 December 2012

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We present a time-resolved study of the logical operation of a polariton condensate transistor switch. Creating a polariton condensate (source) in a GaAs ridge-shaped microcavity with a non-resonant pulsed laser beam, the polariton propagation towards a collector, at the ridge edge, is controlled by a second weak pulse (gate), located between the source and the collector. The experimental results are interpreted in the light of simulations based on the generalized Gross-Pitaevskii equation, including incoherent pumping, decay, and energy relaxation within the condensate.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
85.30.Tv Field effect devices
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Master-oscillator power-amplifier quantum cascade laser array

P. Rauter, S. Menzel, A. K. Goyal, B. Gökden, C. A. Wang, A. Sanchez, G. W. Turner, and F. Capasso

Appl. Phys. Lett. 101, 261117 (2012); http://dx.doi.org/10.1063/1.4773377 (4 pages) | Cited 2 times

Online Publication Date: 28 December 2012

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We report on the demonstration of an array of master-oscillator power-amplifier quantum cascade lasers (QCLs) operating in single-mode at different wavelengths between 9.2 and 9.8 μm. In each device, the output of a distributed feedback QCL is injected into a tapered QCL section which acts as an amplifier while maintaining a high beam quality due to adiabatic mode spreading. All array elements feature longitudinal as well as transverse single-mode emission at peak powers between 0.8 and 3.9 W at room temperature. The high output power and excellent beam quality render the array highly suitable for stand-off spectroscopy applications.
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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

Analysis of optical and electrical crosstalk in small pitch photon trapping HgCdTe pixel arrays

J. Schuster and E. Bellotti

Appl. Phys. Lett. 101, 261118 (2012); http://dx.doi.org/10.1063/1.4773484 (4 pages)

Online Publication Date: 28 December 2012

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We have investigated the optical and electrical crosstalk in HgCdTe photovoltaic pixel arrays employing a photon trapping (PT) structure realized with a periodic array of pillars. We have used a finite-difference time-domain approach to compute the carrier generation rate in the device and evaluate the optical crosstalk. Subsequently, solving the drift-diffusion equations, we have computed the quantum efficiency and the electrical crosstalk. We have found that, compared to a conventional pixel array, the one employing the photon trapping structure has a slightly higher optical crosstalk. However, the presence of the photon trapping region drastically reduces the electrical (total) crosstalk.
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42.50.Wk Mechanical effects of light on material media, microstructures and particles
02.70.Bf Finite-difference methods

Subterahertz electromagnetic wave generation in a randomly networked single-walled carbon nanotubes photoconductive switch

Jun-Hwan Shin, Jeong-Woo Park, Sang-Pil Han, Pulak C. Debnath, Yong-Won Song, Namje Kim, Han-Cheol Ryu, Hyunsung Ko, and Kyung Hyun Park

Appl. Phys. Lett. 101, 261119 (2012); http://dx.doi.org/10.1063/1.4773487 (4 pages)

Online Publication Date: 28 December 2012

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We demonstrated an electromagnetic (EM) wave generation that reaches up to 250 GHz in the photoconductive switch based on randomly networked single-walled carbon nanotubes (SWNTs). Furthermore, we investigated the bias dependence of the electromagnetic wave amplitudes. This subterahertz radiation is generated by the acceleration of photogenerated carriers through fluctuation-induced tunneling in single-walled carbon nanotube bundles. Below the bias field of 20 kV/cm, the signal was enhanced with an increase in the bias field. However, the signal amplitudes decreased above 20 kV/cm due to emerging space-charge accumulation and scattering effect occurring at the defects and contact points.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
85.35.Kt Nanotube devices
41.20.Jb Electromagnetic wave propagation; radiowave propagation
84.32.Dd Connectors, relays, and switches

Fano interpretation of second harmonic generation in a photonic crystal on a gel

Ljubiša Babić, Louwrens T. H. van Dellen, and Michiel J. A. de Dood

Appl. Phys. Lett. 101, 261120 (2012); http://dx.doi.org/10.1063/1.4773513 (4 pages)

Online Publication Date: 28 December 2012

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We observe a 104 times enhancement of the second harmonic generation of 1.535 μm laser light in a two-dimensional AlGaAs photonic crystal at normal incidence. The linear properties of the optical modes that are resonant with the fundamental frequency are well described by a Fano model and have a typical quality factor of 100. We present an extended version of the Fano interpretation to quantitatively analyze the second harmonic signal using the measured linear properties as input and find good agreement with the data.
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42.70.Qs Photonic bandgap materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
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Measurement of the valence band-offset in a PbSe/ZnO heterojunction by x-ray photoelectron spectroscopy

Lin Li, Jijun Qiu, Binbin Weng, Zijian Yuan, Xiaomin Li, Xiaoyan Gan, Ian R. Sellers, and Zhisheng Shi

Appl. Phys. Lett. 101, 261601 (2012); http://dx.doi.org/10.1063/1.4773512 (4 pages)

Online Publication Date: 26 December 2012

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A heterojunction of PbSe/ZnO has been grown by molecular beam epitaxy. X-ray photoelectron spectroscopy was used to directly measure the valence-band offset (VBO) of the heterojunction. The VBO, ΔEV, was determined as 2.51 ± 0.05 eV using the Pb 4p3/2 and Zn 2p3/2 core levels as a reference. The conduction-band offset, ΔEC, was, therefore, determined to be 0.59 ± 0.05 eV based on the above ΔEV value. This analysis indicates that the PbSe/ZnO heterojunction forms a type I (Straddling Gap) heterostructure.
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73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.55.ag Semiconductors

Epitaxial growth of (111)-oriented LaAlO3/LaNiO3 ultra-thin superlattices

S. Middey, D. Meyers, M. Kareev, E. J. Moon, B. A. Gray, X. Liu, J. W. Freeland, and J. Chakhalian

Appl. Phys. Lett. 101, 261602 (2012); http://dx.doi.org/10.1063/1.4773375 (3 pages)

Online Publication Date: 27 December 2012

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The epitaxial stabilization of a single layer or superlattice structures composed of complex oxide materials on polar (111) surfaces is severely burdened by the reconstructions at the interface that commonly arise to neutralize the polarity. We report on the synthesis of high quality LaNiO3/mLaAlO3 pseudo cubic (111) superlattices on polar (111)-oriented LaAlO3, the proposed complex oxide candidate for a topological insulating behavior. Comprehensive X-Ray diffraction measurements, reflection high energy electron diffraction, and element specific resonant X-ray absorption spectroscopy affirm their high structural and chemical quality. The study offers an opportunity to fabricate interesting interface and topology controlled (111)-oriented superlattices based on ortho-nickelates.
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68.55.aj Insulators
68.35.Ct Interface structure and roughness
73.21.Cd Superlattices
78.70.Dm X-ray absorption spectra
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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Spatial resolution of synchrotron x-ray microtomography in high energy range: Effect of x-ray energy and sample-to-detector distance

D. Seo, F. Tomizato, H. Toda, K. Uesugi, A. Takeuchi, Y. Suzuki, and M. Kobayashi

Appl. Phys. Lett. 101, 261901 (2012); http://dx.doi.org/10.1063/1.4773239 (5 pages)

Online Publication Date: 26 December 2012

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Spatial resolution of three-dimensional images obtained by synchrotron X-ray microtomography technique is evaluated using cyclic bar patterns machined on a steel wire. Influences of X-ray energy and the sample-to-detector distance on spatial resolution were investigated. High X-ray energies of 33-78 keV are applied due to the high X-ray absorption of transition metals. Best spatial resolution of about 1.2 μm pitch was observed at the sample-to-detector distance range of 20-110 mm and at the energy range of 68-78 keV. Several factors such as X-ray scattering and diffraction phenomena affecting the degradation of spatial resolution are also discussed.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
07.85.Tt X-ray microscopes

Non-perpendicular hypersonic and optical stop-bands in porous silicon multilayers

J. Manzanares-Martinez, D. Moctezuma-Enriquez, Y. J. Rodriguez-Viveros, B. Manzanares-Martinez, and P. Castro-Garay

Appl. Phys. Lett. 101, 261902 (2012); http://dx.doi.org/10.1063/1.4773243 (4 pages)

Online Publication Date: 26 December 2012

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We study by theoretical simulations the non-perpendicular propagation of electromagnetic and elastic waves in porous silicon multilayers. We proceeded in three steps. First, we found the conditions to obtain a simultaneous photonic-phononic mirror at normal incidence. Second, we determined the angular variation of the mirrors computing the projected band structure. In a third step, we found out, on the one hand, that there are no conditions to obtain an omnidirectional mirror for electromagnetic waves. But, on the other hand, we found the conditions were possible to obtain an omnidirectional mirror for elastic waves. Moreover, the elastic mirror is revealed to be a polarization-converter due to the conversion of evanescent modes in the band gap.
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78.66.Db Elemental semiconductors and insulators
81.05.Rm Porous materials; granular materials
61.43.Gt Powders, porous materials
62.30.+d Mechanical and elastic waves; vibrations
68.65.Ac Multilayers

Dielectric function spectra at 40 K and critical-point energies for CuIn0.7Ga0.3Se2

S. G. Choi, R. Chen, C. Persson, T. J. Kim, S. Y. Hwang, Y. D. Kim, and L. M. Mansfield

Appl. Phys. Lett. 101, 261903 (2012); http://dx.doi.org/10.1063/1.4773362 (4 pages) | Cited 1 time

Online Publication Date: 26 December 2012

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We report ellipsometrically determined dielectric function ε spectra for CuIn0.7Ga0.3Se2 thin film at 40 and 300 K. The data exhibit numerous spectral features associated with interband critical points (CPs) in the spectral range from 0.74 to 6.43 eV. The second-energy-derivatives of ε further reveal a total of twelve above-bandgap CP features, whose energies are obtained accurately by a standard lineshape analysis. The ε spectra determined by ellipsometry show a good agreement with the results of full-potential linearized augmented plane wave calculations. Probable electronic origins of the CP features observed are discussed.
Show PACS
78.66.Li Other semiconductors
82.60.-s Chemical thermodynamics
07.60.Fs Polarimeters and ellipsometers
68.55.-a Thin film structure and morphology
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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