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25 Apr 2011

Volume 98, Issue 17, Articles (17xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 171102 (2011); http://dx.doi.org/10.1063/1.3582035 (3 pages)

Shigeru Nakayama, Satomi Ishida, Satoshi Iwamoto, and Yasuhiko Arakawa
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Enhanced protein binding on femtosecond laser ablated poly(methyl methacrylate) surfaces

Xiaodong Ma, Haibin Huo, Ming Wei, Lingling Wang, Mengyan Shen, Carol Barry, and Joey Mead

Appl. Phys. Lett. 98, 171101 (2011); http://dx.doi.org/10.1063/1.3583981 (3 pages) | Cited 1 time

Online Publication Date: 25 April 2011

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Poly(methyl methacrylate) (PMMA) substrates were ablated through a fast femtosecond (fs) laser scanning process to create patterns for enhanced protein binding. Typically, two patterns with lines and grids were produced and the protein binding was evaluated by studying the adsorption of fluorescein isothiocyanate (FITC)-labeled bovine serum albumin (BSA). It was found that the adsorption of FITC-BSA was increased up to tenfold on both patterns compared with the untreated PMMA surface, indicating the potential application of the fs laser ablated PMMA surfaces as protein assay substrates.
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87.85.mk Proteomics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
87.15.R- Reactions and kinetics

Effect of cavity mode volume on photoluminescence from silicon photonic crystal nanocavities

Shigeru Nakayama, Satomi Ishida, Satoshi Iwamoto, and Yasuhiko Arakawa

Appl. Phys. Lett. 98, 171102 (2011); http://dx.doi.org/10.1063/1.3582035 (3 pages) | Cited 5 times

Online Publication Date: 25 April 2011

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We experimentally investigated photoluminescence (PL) from silicon photonic crystal nanocavities with different mode volumes at room temperature. The integrated cavity mode intensity, which was estimated from the observed PL signal by considering extraction and collection efficiencies for each cavity mode, increased as the cavity mode volume decreased. This result suggests that smaller cavities have larger mode emission efficiency per volume than that for larger cavities at room temperature.
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78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors

Low-threshold green laser heterostructures with Zn(Mg)SSe/ZnSe graded-index superlattice waveguide: Structural and optical properties

I. V. Sedova, E. V. Lutsenko, S. V. Gronin, S. V. Sorokin, A. G. Vainilovich, A. A. Sitnikova, G. P. Yablonskii, A. Alyamani, D. L. Fedorov, P. S. Kop’ev, and S. V. Ivanov

Appl. Phys. Lett. 98, 171103 (2011); http://dx.doi.org/10.1063/1.3579543 (3 pages) | Cited 2 times

Online Publication Date: 25 April 2011

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We report on structural and optical properties of green (λ ∼ 520 nm) ZnCdSe/ZnMgSSe optically pumped laser heterostructures with a Zn(Mg)SSe/ZnSe graded-index superlattice (SL) waveguide, grown by molecular beam epitaxy. The pseudomorphic 400 nm thick waveguide comprising a set of strained ZnMgSSe/ZnSe and ZnSSe/ZnSe SLs of different periods and barrier-to-well thickness ratios at each side of a ZnCdSe quantum well (QW) active region provides efficient transport of nonequilibrium carriers to the QW. This results in reduction in laser threshold down to the extremely low value of 1.5 kW/cm2 at 300 K and increasing the external quantum efficiency above 44%.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
84.40.Az Waveguides, transmission lines, striplines

Three-dimensional surface profiling and optical characterization of liquid microlens using a Shack–Hartmann wave front sensor

Chenhui Li, Gunnsteinn Hall, Xuefeng Zeng, Difeng Zhu, Kevin Eliceiri, and Hongrui Jiang

Appl. Phys. Lett. 98, 171104 (2011); http://dx.doi.org/10.1063/1.3583379 (3 pages) | Cited 1 time

Online Publication Date: 26 April 2011

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We demonstrate three-dimensional (3D) surface profiling of the water–oil interface in a tunable liquid microlens using a Shack–Hartmann wave front sensor. The principles and the optical setup for achieving 3D surface measurements are presented and a hydrogel-actuated liquid lens was measured at different focal lengths. The 3D surface profiles are then used to study the optical properties of the liquid lens. Our method of 3D surface profiling could foster the improvement of liquid lens design and fabrication, including surface treatment and aberration reduction.
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42.79.Bh Lenses, prisms and mirrors
42.79.Pw Imaging detectors and sensors
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.60.-j Optical instruments and equipment

An ultrafast quantum random number generator with provably bounded output bias based on photon arrival time measurements

Michael Wahl, Matthias Leifgen, Michael Berlin, Tino Röhlicke, Hans-Jürgen Rahn, and Oliver Benson

Appl. Phys. Lett. 98, 171105 (2011); http://dx.doi.org/10.1063/1.3578456 (3 pages) | Cited 5 times

Online Publication Date: 26 April 2011

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We report the implementation of a quantum random number generator based on photon arrival times. Due to fast and high resolution timing we are able to generate the highest bitrate of any current generator based on photon arrival times. Bias in the raw data due to the exponential distribution of the arrival times is removed by postprocessing which is directly integrated in the field programmable logic of the timing electronics.
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84.30.Sk Pulse and digital circuits
85.60.Jb Light-emitting devices
85.60.Ha Photomultipliers; phototubes and photocathodes

Manipulation of multidimensional plasmonic spectra for information storage

Wei Ting Chen, Pin Chieh Wu, Chen Jung Chen, Chun-Jen Weng, Hsin-Chen Lee, Ta-Jen Yen, Chieh-Hsiung Kuan, Masud Mansuripur, and Din Ping Tsai

Appl. Phys. Lett. 98, 171106 (2011); http://dx.doi.org/10.1063/1.3584020 (3 pages) | Cited 2 times

Online Publication Date: 27 April 2011

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We demonstrate a concept of optical data storage through plasmonic resonances of metallic nanostructures. Metallic nanostructures exhibit strong variations in their reflectance and/or transmittance spectra due to surface plasmon polariton resonances. We study the variations in spectra through 50×50 arrays of repeated unit cells covering a total area of ∼ 50×50 μm2. Each cell contains ten different nanofeatures, such as an ellipse, a ring, a circle, a triangle, a square, etc. The size of each unit-cell is 500×500 nm2, and the periodicity is 1.0 μm. The variations in spectra are obvious enough to be distinguished and then retrieved.
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78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
42.79.Vb Optical storage systems, optical disks

Structured scintillator for hard x-ray grating interferometry

Simon Rutishauser, Irene Zanette, Tilman Donath, Anna Sahlholm, Jan Linnros, and Christian David

Appl. Phys. Lett. 98, 171107 (2011); http://dx.doi.org/10.1063/1.3583464 (3 pages) | Cited 3 times

Online Publication Date: 27 April 2011

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Grating interferometry at conventional x-ray tubes improves the quality of radiographies and tomograms by providing phase and scattering contrast data. The main challenge encountered when applying this technique at high photon energies, as required by many applications to obtain sufficient penetration depth, is to maintain a high fringe visibility. In this letter, we report on a substantial improvement in fringe visibility and according improvements in image quality achieved by replacing the absorbing analyzer grating of the interferometer with a structured scintillator grating. This development represents a significant step toward the implementation of this technique in industrial testing and medical applications.
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07.85.-m X- and γ-ray instruments
07.60.Ly Interferometers

Detailed balance limit of the efficiency of multilevel intermediate band solar cells

Tomohiro Nozawa and Yasuhiko Arakawa

Appl. Phys. Lett. 98, 171108 (2011); http://dx.doi.org/10.1063/1.3583587 (3 pages) | Cited 11 times

Online Publication Date: 27 April 2011

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Intermediate-band solar cells (IBSCs) promise ultrahigh solar-electricity energy conversion. We have calculated the detailed balance limit of the efficiency for IBSCs with multiple intermediate bands by optimizing IB’s energy levels. The results indicate that thermodynamic limit of IBSCs with 4 IBs is 74.6% which far exceeds 63% calculated in a previous study for the single IB case. By further increasing the total number IBs, the thermodynamic limit of IBSCs can ultimately approach nearly 80%.
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88.40.H- Solar cells (photovoltaics)
88.40.J- Types of solar cells

Enhancement of nonreciprocal phase shift by magneto-optical slot waveguide with a compensation wall

Wenfu Zhang, Jian-Wei Mu, Wei-Ping Huang, and Wei Zhao

Appl. Phys. Lett. 98, 171109 (2011); http://dx.doi.org/10.1063/1.3584035 (3 pages) | Cited 3 times

Online Publication Date: 28 April 2011

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We demonstrated that the nonreciprocal phase shift (NPS) can be efficiently enhanced by introducing a low-index magneto-optical (MO) slot with a compensation wall (CW) in a high-index non-MO waveguide. The proposed structure has been examined by a perturbation theory and it is found that by adjusting the slot width and waveguide height, more than 20 times enhancement of NPS comparing with the rib waveguide with a CW can be realized.
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42.79.Gn Optical waveguides and couplers
85.70.Sq Magnetooptical devices

Statistical optoacoustic image reconstruction using a-priori knowledge on the location of acoustic distortions

X. Luís Deán-Ben, Vasilis Ntziachristos, and Daniel Razansky

Appl. Phys. Lett. 98, 171110 (2011); http://dx.doi.org/10.1063/1.3564905 (3 pages) | Cited 2 times

Online Publication Date: 28 April 2011

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Strong reflection and scattering effects, arising at the boundaries of acoustically mismatched areas in living organisms, such as bones, lungs, and other air cavities, may introduce severe image artifacts into optoacoustic reconstructions. Yet, in many cases, an a priori knowledge on the location of strongly mismatched areas is available, either based on general anatomical knowledge or using other imaging modalities. In this letter, we suggest a statistical optoacoustic image reconstruction method, which uses a priori knowledge on the location of acoustic distortions in order to improve image quality and quantification. Significant improvements are showcased experimentally on tissue mimicking phantoms of different complexities.
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87.63.D- Ultrasonography
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
87.57.cp Artifacts and distortion
87.57.nf Reconstruction
43.58.Ry Distortion: frequency, nonlinear, phase, and transient; measurement of distortion
FREE

Large optical gain AlGaN-delta-GaN quantum wells laser active regions in mid- and deep-ultraviolet spectral regimes

Jing Zhang, Hongping Zhao, and Nelson Tansu

Appl. Phys. Lett. 98, 171111 (2011); http://dx.doi.org/10.1063/1.3583442 (3 pages) | Cited 26 times

Online Publication Date: 28 April 2011

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The gain characteristics of high Al-content AlGaN-delta-GaN quantum wells (QWs) are investigated for mid- and deep-ultraviolet (UV) lasers. The insertion of an ultrathin GaN layer in high Al-content AlGaN QWs leads to valence subbands rearrangement, which in turn results in large optical gain for mid- and deep-UV lasers.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.By Design of specific laser systems
42.72.Bj Visible and ultraviolet sources
73.20.At Surface states, band structure, electron density of states
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Nanometer-scale epitaxial strain release in perovskite heterostructures using “SrAlOx” sliding buffer layers

H. K. Sato, J. A. Mundy, T. Higuchi, Y. Hikita, C. Bell, D. A. Muller, and H. Y. Hwang

Appl. Phys. Lett. 98, 171901 (2011); http://dx.doi.org/10.1063/1.3583459 (3 pages) | Cited 1 time

Online Publication Date: 25 April 2011

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We demonstrate the strain release of LaAlO3 epitaxial films on SrTiO3 (001) by inserting ultrathin “SrAlOx” buffer layers. Although SrAlOx is not a perovskite, nor stable as a single phase in bulk, epitaxy stabilizes the perovskite structure up to a thickness of 2 unit cells (uc). At a critical thickness of 3 uc of SrAlOx, the interlayer acts as a sliding buffer layer, and abruptly relieves the lattice mismatch between the LaAlO3 film and the SrTiO3 substrate, while maintaining crystallinity. This technique may provide a general approach for strain relaxation of perovskite films far below the thermodynamic critical thickness.
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68.55.aj Insulators
68.60.Bs Mechanical and acoustical properties

Direct determination of flat-band voltage for metal/high κ oxide/semiconductor heterointerfaces by electric-field-induced second-harmonic generation

C.-L. Chang, W. C. Lee, L. K. Chu, M. Hong, J. Kwo, and Y.-M. Chang

Appl. Phys. Lett. 98, 171902 (2011); http://dx.doi.org/10.1063/1.3583463 (3 pages) | Cited 1 time

Online Publication Date: 25 April 2011

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We have employed electric-field-induced second-harmonic (EFISH) generation to determine the flat-band voltage (VFB) of Cr/ALD-Al2O3/MBE-HfO2/n-Si (001) MOS structure. Due to the phase sensitivity of EFISH signal to the electric field in the space charge region, the VFB of −1.20±0.07 V was determined by analyzing the relative phase change in the EFISH signal as a function of the applied gate voltage. The obtained value is in good agreement with that estimated by the capacitance-voltage measurement. This study demonstrated an all-optical technique to directly determine the flat-band voltage for the high κ oxide/Si heterointerfaces.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
77.22.Jp Dielectric breakdown and space-charge effects
68.35.Ct Interface structure and roughness
78.20.Jq Electro-optical effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

In situ probing of helium desorption from individual nanobubbles under electron irradiation

M.-L. David, F. Pailloux, V. Mauchamp, and L. Pizzagalli

Appl. Phys. Lett. 98, 171903 (2011); http://dx.doi.org/10.1063/1.3582612 (3 pages) | Cited 2 times

Online Publication Date: 26 April 2011

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The understanding of the mechanisms of helium bubble formation and evolution in materials requires the quantitative determination of several key quantities such as the helium density in the bubbles. Helium nanobubbles of about 16 nm in diameter were created in silicon by helium implantation at high fluence and subsequent annealing. Individual nanobubbles were analyzed by spatially resolved Electron Energy-loss Spectroscopy (EELS). We report on the in situ probing of helium desorption from the nanobubbles under electron irradiation. This opens new perspectives for a more accurate determination of the helium density through spatially resolved EELS.
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68.43.Nr Desorption kinetics
61.80.Fe Electron and positron radiation effects
79.20.Uv Electron energy loss spectroscopy
81.40.Gh Other heat and thermomechanical treatments

Saturable absorbing dynamics of GaInN multiquantum well structures

Takao Miyajima, Shunsuke Kono, Hideki Watanabe, Tomoyuki Oki, Rintaro Koda, Masaru Kuramoto, Masao Ikeda, and Hiroyuki Yokoyama

Appl. Phys. Lett. 98, 171904 (2011); http://dx.doi.org/10.1063/1.3583456 (3 pages) | Cited 2 times

Online Publication Date: 26 April 2011

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We evaluated saturation energies and absorption recovery time dependent on reverse-bias voltage for a waveguide-coupled GaInN multiquantum well saturable absorber in a bisectional laser structure. When the applied reverse-bias was increased from 5 to 20 V, the saturation energy at 405 nm monotonically increased from 5 to 14 pJ; the linear absorption coefficient at 405 nm showed the same dependence. These dependences are different from those observed in an AlGaAs multiquantum well. The absorption recovery time was shortened to 3 ps when a highly reverse-bias voltage of 20 V was applied.
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42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption

In search of energy landscape for network glasses

Roman Golovchak, Andriy Kovalskiy, Oleh Shpotyuk, and Himanshu Jain

Appl. Phys. Lett. 98, 171905 (2011); http://dx.doi.org/10.1063/1.3583531 (3 pages) | Cited 3 times

Online Publication Date: 26 April 2011

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Quick scanning extended x-ray absorption fine-structure spectroscopy is used to obtain in situ structural information on the real-time response of network glasses at the nanoscale level of atomic organization to the temperature ramp through the glass transition range. The results testify nonlinear, real-time temperature response indicative of nanoscale dynamic heterogeneity in disordered systems with intermediate fragility, related to the intermetabasin transitions within potential energy/enthalpy landscape.
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61.43.Fs Glasses
64.70.pe Metallic glasses
78.70.Dm X-ray absorption spectra
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.

Light-induced structural changes in Eu-doped (Pb,La)(Zr,Ti)O3 ceramics

Thandar Myint, Ray Gunawidjaja, and Hergen Eilers

Appl. Phys. Lett. 98, 171906 (2011); http://dx.doi.org/10.1063/1.3584136 (3 pages) | Cited 3 times

Online Publication Date: 27 April 2011

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Fluorescence spectra of poled and unpoled Eu-doped (Pb,La)(Zr,Ti)O3 ceramics with various compositions were measured using 580 nm excitation. The ratio of the intensities of the Eu3+ 5D0→7F2/5D0→7F1 fluorescence transitions was used as an indicator for the symmetry of the Eu3+ site. As the symmetry decreases, the ratio increases. Increasing the Zr content in (Pb,La)(Zr,Ti)O3 increases the ratio, indicating that the symmetry of the Eu3+ site decreases. Exposure of the Eu-doped (Pb,La)(Zr,Ti)O3 samples to UV light also increases the intensity ratio, indicating that UV light exposure leads to structural distortions in Eu-doped (Pb,La)(Zr,Ti)O3 samples, lowering the Eu3+ site symmetry.
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78.55.Hx Other solid inorganic materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Observation of slow-light in a metamaterials waveguide at microwave frequencies

Salvatore Savo, B. D. F. Casse, Wentao Lu (陆文韬), and Srinivas Sridhar

Appl. Phys. Lett. 98, 171907 (2011); http://dx.doi.org/10.1063/1.3583521 (3 pages) | Cited 3 times

Online Publication Date: 27 April 2011

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We report an experimental observation of slow-light in the GHz microwave regime utilizing the mechanism of the degeneracy of forward and backward waves in a planar waveguide consisting of a dielectric core cladded by single-negative metamaterial. The metamaterial cladding consists of periodic arrays of metallic split-ring resonators, exhibiting an effective negative permeability. Group delay dispersions obtained from pulsed measurements are in complete agreement with theoretical predictions.
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42.65.Wi Nonlinear waveguides
42.70.-a Optical materials
78.70.Gq Microwave and radio-frequency interactions

Observation of surface-guided waves in holey hypersonic phononic crystal

Sarah Benchabane, Olivier Gaiffe, Gwenn Ulliac, Roland Salut, Younes Achaoui, and Vincent Laude

Appl. Phys. Lett. 98, 171908 (2011); http://dx.doi.org/10.1063/1.3583982 (3 pages) | Cited 6 times

Online Publication Date: 28 April 2011

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We observe experimentally the propagation of surface-guided waves in a hypersonic phononic crystal, both in the radiative and nonradiative regions of the spectrum. Combining electrical measurements in reflection and transmission as well as optical maps of the surface displacement, a band gap extending from 0.6 to 0.95 GHz is identified in a square lattice array of 1 μm radius air holes milled in lithium niobate. The optical measurements reveal the transmission of surface-guided waves above the band gap, well inside the sound cone.
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63.20.-e Phonons in crystal lattices
71.20.Ps Other inorganic compounds
68.35.Iv Acoustical properties

Quality factor in clamping loss of nanocantilever resonators

Jin Hwan Ko, Joonho Jeong, Jinbok Choi, and Maenghyo Cho

Appl. Phys. Lett. 98, 171909 (2011); http://dx.doi.org/10.1063/1.3575560 (3 pages) | Cited 1 time

Online Publication Date: 28 April 2011

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Clamping loss caused by elastic wave radiation to a support is one of the most dominant loss mechanisms in predicting the quality factor of very or ultra high frequency nanocantilever resonators. To consider nanosurface effects and different scales of the resonator and support, we propose a multiscale model combining a scale-bridging model for the resonator and a perfectly matched layer to estimate the loss in the support. The proposed model is used to investigate the surface effect on the nanoresonator and also shows the tradeoff between the resonant frequency and the quality factor with or without the surface effects.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Metallic characteristics in superlattices composed of insulators, NdMnO3/SrMnO3/LaMnO3

J. W. Seo, B. T. Phan, J. Lee, H.-D. Kim, and C. Panagopoulos

Appl. Phys. Lett. 98, 171910 (2011); http://dx.doi.org/10.1063/1.3583586 (3 pages)

Online Publication Date: 28 April 2011

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We report on the electronic properties of superlattices composed of three different antiferromagnetic insulators, NdMnO3/SrMnO3/LaMnO3 grown on SrTiO3 substrates. Photoemission spectra obtained by tuning the x-ray energy at the Mn 2p→3d edge show a Fermi cut-off, indicating metallic behavior mainly originating from Mn eg electrons. Furthermore, the density of states near the Fermi energy and the magnetization obey a similar temperature dependence, suggesting a correlation between the spin and charge degrees of freedom at the interfaces of these oxides.
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73.21.Ac Multilayers
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states

Focusing of the lowest antisymmetric Lamb wave in a gradient-index phononic crystal plate

Tsung-Tsong Wu, Yan-Ting Chen, Jia-Hong Sun, Sz-Chin Steven Lin, and Tony Jun Huang

Appl. Phys. Lett. 98, 171911 (2011); http://dx.doi.org/10.1063/1.3583660 (3 pages) | Cited 7 times

Online Publication Date: 28 April 2011

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In this letter, we numerically demonstrate focusing of the lowest antisymmetric Lamb wave in a gradient-index phononic crystal (PC) silicon plate and its application as a beam-width compressor for compressing Lamb wave into a stubbed phononic tungsten/silicon plate waveguide. The results show that beam width of the lowest antisymmetric Lamb wave in the PC thin plate can be compressed efficiently and fitted into tungsten/silicon PC plate waveguide over a wide range of frequency.
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63.20.-e Phonons in crystal lattices
68.35.Iv Acoustical properties
43.58.-e Acoustical measurements and instrumentation
43.20.Mv Waveguides, wave propagation in tubes and ducts

A way to determine the permittivity of metallized surfaces at terahertz frequencies

V. V. Gerasimov, B. A. Knyazev, A. K. Nikitin, and G. N. Zhizhin

Appl. Phys. Lett. 98, 171912 (2011); http://dx.doi.org/10.1063/1.3584130 (3 pages) | Cited 1 time

Online Publication Date: 29 April 2011

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A method for determining the dielectric permittivity of metal surfaces at terahertz (THz) frequencies has been suggested and tested. The method implies excitation of surface plasmons (SPs) on the sample surface and measurements of the SPs propagation length and field penetration depth in air. The technique was tested on evaporated gold with Novosibirsk free-electron laser at the wavelength of 130 μm. The method suggested paves the way for refractometry of metallized surfaces at THz frequencies.
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77.22.Ch Permittivity (dielectric function)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces
78.70.Gq Microwave and radio-frequency interactions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

High resolution study of the strong diamond/silicon nitride interface

F. A. Almeida, F. J. Oliveira, R. F. Silva, D. L. Baptista, S. B. Peripolli, and C. A. Achete

Appl. Phys. Lett. 98, 171913 (2011); http://dx.doi.org/10.1063/1.3584019 (3 pages) | Cited 1 time

Online Publication Date: 29 April 2011

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Silicon nitride (Si3N4) is known to offer the required adhesion to chemically vapor deposited diamond coatings for demanding mechanical solicitations but the nature of their strong interface is not well know. Focused ion beam preparation preserved such thin layer for high resolution transmission electron microscopy. Contrarily to earlier suppositions, SiC interlinking particles were not found. Instead, the interface shows diamondlike carbon interlayers (approximately 3nm in thickness) intercalated with regions of directly-grown nanomicrometric and submicrometric-diamond crystals. A grain-to-grain epitaxial relationship of the type 〈111〉Dia∥〈010〉Si3N4 and {111}Dia∥{math20}Si3N4 is observed, concomitant with a 7:1 match arrangement, which assists on the interface strength.
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68.37.Og High-resolution transmission electron microscopy (HRTEM)
68.35.Np Adhesion
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ug Diamond

Polarization analysis of luminescence for the characterization of silicon wafer solar cells

Matthew P. Peloso, Bram Hoex, and Armin G. Aberle

Appl. Phys. Lett. 98, 171914 (2011); http://dx.doi.org/10.1063/1.3584857 (3 pages) | Cited 4 times

Online Publication Date: 29 April 2011

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Luminescence imaging is routinely used to extract important information from photovoltaic materials and devices. We extend the existing luminescence imaging technique to yield the partial polarization of luminescence. It is observed that certain material structures of silicon wafer solar cells generate strongly polarized luminescence. The luminescence polarization effect is related to internal charge anisotropy of certain defects in the silicon wafer solar cells. These observations may be used, for example, to advance the characterization of solar cells, to understand the electrical properties of defects in silicon wafer solar cells, or to study the formation of defects during crystal growth.
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88.40.jj Silicon solar cells
78.55.Ap Elemental semiconductors
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