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10 Dec 2007

Volume 91, Issue 24, Articles (24xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 241101 (2007); http://dx.doi.org/10.1063/1.2821382 (3 pages)

S. N. Goda, S. Sensarn, M. Y. Shverdin, and G. Y. Yin
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Coherent control of molecular modulation

S. N. Goda, S. Sensarn, M. Y. Shverdin, and G. Y. Yin

Appl. Phys. Lett. 91, 241101 (2007); http://dx.doi.org/10.1063/1.2821382 (3 pages) | Cited 1 time

Online Publication Date: 10 December 2007

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We demonstrate coherent control of a molecular modulation process using an incident set of seven optical sidebands spanning two octaves of bandwidth. We utilize a genetic algorithm to optimize the relative phases of the incident sidebands to generate additional UV sidebands with nearly 1% efficiency, change the ratio of energy between sidebands by more than a factor of 50, and efficiently alter individual sideband energies by millijoules.
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42.25.Kb Coherence

Continuous wave terahertz generation up to 2 THz by photomixing on ion-irradiated In0.53Ga0.47As at 1.55 μm wavelengths

J. Mangeney, A. Merigault, N. Zerounian, P. Crozat, K. Blary, and J. F. Lampin

Appl. Phys. Lett. 91, 241102 (2007); http://dx.doi.org/10.1063/1.2817607 (3 pages) | Cited 14 times

Online Publication Date: 10 December 2007

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We report the generation of continuous terahertz waves from microwave frequencies of up to 2 THz obtained by photomixing two optical waves at 1.55 μm wavelengths in ion-irradiated In0.53Ga0.47As interdigitated photomixers. A 200 nm thick silicon nitride coating is used for antireflection and passivation layer, improving the reliability and the heat tolerance of the photomixer. In such devices, output powers greater than 40 nW at 0.5 THz and 10 nW at 1 THz have been achieved. Considering the observed saturation of the output power with the increase of bias voltage, the optimum excitation conditions regarding optical power and bias voltage are discussed.
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61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
81.65.Rv Passivation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Holographically fabricated photonic crystals with large reflectance

Y. C. Chen, J. B. Geddes, III, J. T. Lee, P. V. Braun, and P. Wiltzius

Appl. Phys. Lett. 91, 241103 (2007); http://dx.doi.org/10.1063/1.2820449 (3 pages) | Cited 8 times

Online Publication Date: 11 December 2007

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We report reflection and transmission spectra from three-dimensional polymer photonic crystals fabricated by holographic lithography. The measured peak reflectance matches that predicted by both a finite-difference time-domain method a simple transfer matrix theory and is ∼ 70%, significantly higher than previous reports of ∼ 30% reflectance.
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42.70.Qs Photonic bandgap materials
42.40.My Applications

Versatile waveguide-coupled optofluidic devices based on liquid core optical ring resonators

Ian M. White, John Gohring, Yuze Sun, Gilmo Yang, Scott Lacey, and Xudong Fan

Appl. Phys. Lett. 91, 241104 (2007); http://dx.doi.org/10.1063/1.2824843 (3 pages) | Cited 5 times

Online Publication Date: 10 December 2007

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A versatile waveguide-coupled optofluidic device using the liquid core optical ring resonator (LCORR) that can be operated with liquid of any refractive index (RI) is theoretically analyzed and experimentally demonstrated. The results confirm the confinement of resonant modes for all sample RIs, and reveal that confined modes in a high-RI core are excited by an external waveguide by resonant tunneling through the LCORR wall. It is further found that a thin wall must be used for effective interaction between the core mode and the waveguide. The results have important applications in optofluidic devices, including sensors, microfluidic lasers, and nonlinear optics.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays

Calorimetric detection of the conical terahertz radiation from femtosecond laser filaments in air

Aurélien Houard, Yi Liu, André Mysyrowicz, and Bernadette Leriche

Appl. Phys. Lett. 91, 241105 (2007); http://dx.doi.org/10.1063/1.2821371 (3 pages) | Cited 10 times

Online Publication Date: 10 December 2007

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The spectral distribution of the conical terahertz emission from a femtosecond laser filament in air is measured with a bolometric detector and a set of filters, confirming that the main part of the emission lies between 0.5 and 3 THz. The efficiency of this terahertz emission is compared with that obtained in air via four wave mixing of femtosecond laser pulses at ω and 2ω in the presence of a plasma.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.20.Fw Calorimeters
42.62.-b Laser applications
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Negative and positive electroluminescence from a compensated p-type germanium in terahertz frequencies

P. K. Chung, J. M. Lin, S. T. Yen, and T. H. Wang

Appl. Phys. Lett. 91, 241106 (2007); http://dx.doi.org/10.1063/1.2824577 (3 pages)

Online Publication Date: 12 December 2007

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Negative luminescence (NL) and positive luminescence in terahertz frequencies were observed from a compensated p-type Ge under various levels of pulse excitations at cryogenic temperatures. The NL spectra accompanying an S-type negative differential resistance phenomenon were attributed to the reduced emission transitions from the excited states to the ground states of the acceptors during the excitation. A possible excitation mechanism is also presented according to the measured data.
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78.60.Fi Electroluminescence
71.20.Mq Elemental semiconductors
71.55.Cn Elemental semiconductors

Multistate fluorescence switching of s-triazine-bridged p-phenylene vinylene polymers

Jungmok Yoo, Taechang Kwon, Bhimrao D. Sarwade, Yuna Kim, and Eunkyoung Kim

Appl. Phys. Lett. 91, 241107 (2007); http://dx.doi.org/10.1063/1.2821308 (3 pages) | Cited 12 times

Online Publication Date: 12 December 2007

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A polymer switch was explored utilizing the redox reaction of iodide ions with highly fluorescent s-triazine (ST)-bridged p-phenylene vinylene (PPV) polymers. The fluorescent polymers were synthesized through the Wittig polycondensation to yield ST-bridged PPV polymers. Utilizing different quenching properties of the polymer with iodine derivatives, the fluorescence of the polymers was modulated electrochemically in a two-electrode device consisting of the fluorescent polymer-doped gel layer containing an iodide and iodine couple and a solid polymer electrolyte layer. The cell showed reversible multistate fluorescence switching in the working potential range of +2 V.
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78.55.Kz Solid organic materials
82.30.-b Specific chemical reactions; reaction mechanisms
82.45.Gj Electrolytes
82.45.Wx Polymers and organic materials in electrochemistry
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
82.70.Gg Gels and sols

Submicrometer photoresponse mapping of nanowire superconducting single-photon detectors

Robert H. Hadfield, Paul A. Dalgarno, John A. O’Connor, Euan Ramsay, Richard J. Warburton, Eric J. Gansen, Burm Baek, Martin J. Stevens, Richard P. Mirin, and Sae Woo Nam

Appl. Phys. Lett. 91, 241108 (2007); http://dx.doi.org/10.1063/1.2824384 (3 pages) | Cited 9 times

Online Publication Date: 13 December 2007

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We report on the photoresponse mapping of nanowire superconducting single-photon detectors using a focal spot significantly smaller than the device area (10×10 μm2). Using a confocal microscope configuration and solid immersion lens, we achieve a spot size of 320 nm full width at half maximum onto the device at 470 nm wavelength. We compare the response maps of two devices: The higher detection efficiency device gives a uniform response, whereas the lower detection efficiency device is limited by a single defect or constriction.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)

Coupling of surface waves in highly defined one-dimensional porous silicon photonic crystals for gas sensing applications

Emiliano Descrovi, Francesca Frascella, Beniamino Sciacca, Francesco Geobaldo, Lorenzo Dominici, and Francesco Michelotti

Appl. Phys. Lett. 91, 241109 (2007); http://dx.doi.org/10.1063/1.2824387 (3 pages) | Cited 22 times

Online Publication Date: 13 December 2007

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We describe the use of one-dimensional porous silicon (p-Si) photonic crystals for guiding TE-polarized surface electromagnetic waves (SEWs). Although bulk and interface roughnesses might deteriorate the optical response of photonic structures, we observed reflection spectra presenting narrow (≲6 nm) reflectivity anomalies associated with SEWs. In analogy with surface plasmons, SEWs are strongly sensitive to surface modifications. As a proof of principle for a sensor, we provide a direct real-time monitoring of the reversible interactions of organic vapors with the p-Si multilayer. We highlight the higher sensitivity of the SEW-based detection scheme as compared to a method exploiting perturbations of waveguide modes.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.70.Qs Photonic bandgap materials
68.35.Ct Interface structure and roughness
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Dynamics of random laser and coherent backscattering of light from ZnO amplifying random medium

T. Sun, Z. R. Qiu, H. M. Su, X. D. Zhang, Z. Q. Zhang, G. K. L. Wong, and K. S. Wong

Appl. Phys. Lett. 91, 241110 (2007); http://dx.doi.org/10.1063/1.2824395 (3 pages) | Cited 4 times

Online Publication Date: 13 December 2007

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We investigated the dynamics of coherent backscattering cone and random laser in a disordered gain medium of ZnO powder. Theoretical fit to the coherent backscattering cone yields a transport mean free path l approximately equal to the probe wavelength λ, indicating that the scattering process is in the strong scattering regime. Supernarrow emissions from the laser are accompanied by enhancement and sharpening of the coherent backscattering cone. This enhanced and sharpened backscattering cone returns to a normal profile within 10–20 ps, indicating an ultrafast gain lifetime in the medium, which is in good agreement with the time-resolved measurement of the random laser emissions.
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81.05.Dz II-VI semiconductors
42.62.-b Laser applications
68.49.-h Surface characterization by particle-surface scattering

Ultralow noise midwave infrared InAs–GaSb strain layer superlattice avalanche photodiode

Shubhrangshu Mallick, Koushik Banerjee, Siddhartha Ghosh, Elena Plis, Jean Baptiste Rodriguez, Sanjay Krishna, and Christoph Grein

Appl. Phys. Lett. 91, 241111 (2007); http://dx.doi.org/10.1063/1.2817608 (3 pages) | Cited 6 times

Online Publication Date: 14 December 2007

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Eye-safe midwavelength infrared InAs–GaSb strain layer superlattice p+-n−-n homojunction avalanche photodiodes (APDs) grown by solid source molecular beam epitaxy were fabricated and characterized. Maximum multiplication gain of 1800 was measured at −20 V at 77 K. Excess noise factors between 0.8 and 1.2 were measured up to gain of 300. Gain of 200 was measured at 120 K. Exponential nature of the gain as a function of reverse bias along with low excess noise factor at higher gain confirms single carrier electron-only impact ionization in the avalanche regime. Decrease in the multiplication gain at higher temperatures correlates with standard APD characteristics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.63.-b Electronic transport in nanoscale materials and structures

High-power wavelength stabilized 970 nm tilted cavity laser with a 41.3 dB side mode suppression ratio

L. Ya. Karachinsky, M. Kuntz, G. Fiol, V. A. Shchukin, N. N. Ledentsov, D. Bimberg, A. R. Kovsh, S. S. Mikhrin, I. I. Novikov, Yu. M. Shernyakov, and M. V. Maximov

Appl. Phys. Lett. 91, 241112 (2007); http://dx.doi.org/10.1063/1.2824835 (3 pages) | Cited 2 times

Online Publication Date: 14 December 2007

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We studied wavelength stabilized all-epitaxial 970 nm spectral range GaAs/GaAlAs tilted cavity lasers (TCLs). Single transverse mode edge-emitting 4-μm-wide ridge lasers demonstrated spatial and spectral single mode continuous wave operation with a longitudinal side mode suppression ratio up to 41.3 dB. Small signal modulation bandwidth of 3 GHz with a resonance peak of 6 dB at the relaxation oscillation frequency was measured for a 870 μm long device. TCL modulation efficiency is 0.36 GHz/(mA)1/2. S-parameter measurements indicate that much higher frequencies may be expected in case of more advanced processing and/or shorter cavity lengths.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Ultrafast carrier dynamics in band edge and broad deep defect emission ZnSe nanowires

Andreas Othonos, Emmanouil Lioudakis, U. Philipose, and Harry E. Ruda

Appl. Phys. Lett. 91, 241113 (2007); http://dx.doi.org/10.1063/1.2825290 (3 pages) | Cited 12 times

Online Publication Date: 14 December 2007

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Ultrafast carrier dynamics of ZnSe nanowires grown under different growth conditions have been studied. Transient absorption measurements reveal the dependence of the competing effects of state filling and photoinduced absorption on the probed energy states. The relaxation of the photogenerated carriers occupying defect states in the stoichiometric and Se-rich samples are single exponentials with time constants of 3–4 ps. State filling is the main contribution for probe energies below 1.85 eV in the Zn-rich grown sample. This ultrafast carrier dynamics study provides an important insight into the role that intrinsic point defects play in the observed photoluminescence from ZnSe nanowires.
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73.63.Nm Quantum wires
71.55.Gs II-VI semiconductors
78.55.Et II-VI semiconductors
78.67.Lt Quantum wires
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Ion beam formation in a low-pressure geometrically expanding argon plasma

C. S. Corr, J. Zanger, R. W. Boswell, and C. Charles

Appl. Phys. Lett. 91, 241501 (2007); http://dx.doi.org/10.1063/1.2823575 (3 pages) | Cited 23 times

Online Publication Date: 10 December 2007

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Supersonic ion beam formation has been observed in a geometrically expanding low-pressure inductively coupled argon plasma. It is found that the ion beam is only observed below 3 mTorr and only when the discharge is operated in inductive mode. The geometrical expansion of the plasma induces density and potential gradients leading to the ion beam formation. The ion beam energy increases with decreasing source tube radius. The results show that ion beam formation can be achieved by geometrical expansion alone and that the ion beam energy depends on the ratio of the cross-sectional area of the source and expansion region.
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52.50.Dg Plasma sources
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Metal induced hydrogen effusion from amorphous silicon

Hiromasa Ohmi, Kiyoshi Yasutake, Yoshinori Hamaoka, and Hiroaki Kakiuchi

Appl. Phys. Lett. 91, 241901 (2007); http://dx.doi.org/10.1063/1.2819086 (3 pages)

Online Publication Date: 10 December 2007

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Hydrogen effusion from hydrogenated amorphous silicon (a-Si:H) films, induced by various metal layers (Al, Ni, Cu, Ge, Cr, Au, Ag, Fe, and Sn), has been studied by temperature programed desorption spectroscopy. Significant reduction of the effusion temperature is observed in the presence of Cr, Ni, or Al on the a-Si:H film. Al has the strongest catalytic effect on hydrogen effusion from a-Si:H; H2 effusion is intensive, even at a temperature of 150 °C, when the Al layer thickness is larger than 40 nm. The strong catalytic effect of Al is considered to be related to the large diffusion constant of Al in a-Si:H.
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68.43.Vx Thermal desorption
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Study of stress in a shallow-trench-isolated Si structure using polarized confocal near-UV Raman microscopy of its cross section

Vladimir Poborchii, Tetsuya Tada, and Toshihiko Kanayama

Appl. Phys. Lett. 91, 241902 (2007); http://dx.doi.org/10.1063/1.2825286 (3 pages) | Cited 16 times

Online Publication Date: 10 December 2007

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Stress in shallow-trench-isolated structures with 250-nm-wide Si stripes was examined by 364 nm excitation confocal Raman microscopy. Using objective lenses with the experimentally measured ∼ 150 nm spatial resolution, we studied polarized Raman spectra from the section perpendicular to the stripes. Detection of two optical phonons enabled us to analyze orientation and intensity of local stress quantitatively. Uniaxial [001] compressive stress was found in the Si substrate under both the trench and the stripe, while the stress in the stripe was uniaxial [110] perpendicular to the stripe.
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68.47.Fg Semiconductor surfaces
81.05.Cy Elemental semiconductors
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Identification of a Ni0.5(Al0.5−xMnx) B2 phase at the heterophase interfaces of Cu-rich precipitates in an α-Fe matrix

R. Prakash Kolli, Zugang Mao, David N. Seidman, and Denis T. Keane

Appl. Phys. Lett. 91, 241903 (2007); http://dx.doi.org/10.1063/1.2820378 (3 pages) | Cited 9 times

Online Publication Date: 11 December 2007

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A phase with the stoichiometry Ni0.5(Al0.5−xMnx) is observed at heterophase interfaces of Cu-rich precipitates in an α-Fe matrix, utilizing atom-probe tomography. First-principles calculations are utilized to determine the substitutional energies, yielding EMn→Ni = 0.916 eV atom−1 and EMn→Al = −0.016 eV atom−1 indicating that the manganese atoms prefer substituting at Al sublattice sites instead of Ni sites. A synchrotron radiation experiment demonstrates that the identified phase possesses the B2 structure.
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68.35.Dv Composition, segregation; defects and impurities
61.66.Bi Elemental solids
61.66.Dk Alloys

Mechanical properties and tuning of three-dimensional polymeric photonic crystals

Saulius Juodkazis, Vygantas Mizeikis, Kock Khuen Seet, Hiroaki Misawa, and Ulrike G. K. Wegst

Appl. Phys. Lett. 91, 241904 (2007); http://dx.doi.org/10.1063/1.2822825 (3 pages) | Cited 9 times

Online Publication Date: 11 December 2007

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Mechanical properties of photopolymerized photonic crystal (PhC) structures having woodpile and spiral three-dimensional architectures were examined using flat-punch indentation. The structures were found to exhibit a foamlike response with a bend-dominated elastic deformation regime observed at strain levels up to 10%. Numerical simulations of optical properties of these PhC structures demonstrate the possibility of achieving a substantial and reversible spectral tuning of the photonic stop gap wavelength by applying a mechanical load to the PhC.
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42.70.Qs Photonic bandgap materials
61.41.+e Polymers, elastomers, and plastics
62.20.Qp Friction, tribology, and hardness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
42.70.Jk Polymers and organics
81.40.Jj Elasticity and anelasticity, stress-strain relations

Suppression of the shear band instability during plastic flow of nanometer-scale confined metallic glasses

A. Donohue, F. Spaepen, R. G. Hoagland, and A. Misra

Appl. Phys. Lett. 91, 241905 (2007); http://dx.doi.org/10.1063/1.2821227 (3 pages) | Cited 46 times

Online Publication Date: 11 December 2007

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The shear band instability that occurs during plastic deformation of metallic glasses limits the application of these high-strength materials. We show that this instability can be suppressed in nanometer-scale metallic glasses constrained by ultrafine crystalline layers. Free-standing Cu/amorphous Pd0.77Si0.23 multilayers consisting either of 10/90 nm glass/Cu or 100/100 nm glass/Cu were deformed to layer thickness reductions greater than 75% by cold rolling or bending, respectively. Transmission electron microscopy showed uniform reduction in the layer thickness with no shear band formation in the amorphous layers. The mechanisms that allow homogeneous codeformation of metallic glasses with nanoscale crystalline layers at high stresses are discussed.
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81.40.Lm Deformation, plasticity, and creep
61.43.Fs Glasses
68.65.Ac Multilayers
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Influences of nonlinearities of loudspeakers on performances of thermoacoustic refrigerators

Li Fan, Shu-yi Zhang, Kai Zheng, and Hui Zhang

Appl. Phys. Lett. 91, 241906 (2007); http://dx.doi.org/10.1063/1.2813616 (3 pages) | Cited 3 times

Online Publication Date: 12 December 2007

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A nonlinear model of an electrodynamic loudspeaker is used to study the influences of the loudspeaker’s nonlinearities on the performances of thermoacoustic refrigerators. The results demonstrate that the nonlinearities of the magnetic field and vibration component of a loudspeaker change the acoustic output power and electroacoustic transfer efficiency. Additionally, the nonlinearity of the vibration component shifts the resonance frequency of the thermoacoustic refrigerator, which induces deviation of the load resistance of the loudspeaker at the resonance frequency. Therefore, the loudspeaker’s nonlinearities influence the acoustic coupling between the loudspeaker and resonance pipe, and also the performances of thermoacoustic refrigerators.
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43.38.Ja Loudspeakers and horns, practical sound sources
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Raman imaging of doping domains in graphene on SiO2

C. Stampfer, F. Molitor, D. Graf, K. Ensslin, A. Jungen, C. Hierold, and L. Wirtz

Appl. Phys. Lett. 91, 241907 (2007); http://dx.doi.org/10.1063/1.2816262 (3 pages) | Cited 38 times

Online Publication Date: 12 December 2007

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We present spatially resolved Raman images of the G and 2D lines of single-layer graphene flakes. The spatial fluctuations of G and 2D lines are correlated and are thus shown to be affiliated with local doping domains. We investigate the position of the 2D line—the most significant Raman peak to identify single-layer graphene—as a function of charging up to ∣n∣ ≈ 4×1012 cm−2. Contrary to the G line which exhibits a strong and symmetric stiffening with respect to electron and hole doping, the 2D line shows a weak and slightly asymmetric stiffening for low doping. Additionally, the linewidth of the 2D line is, in contrast to the G line, doping independent making this quantity a reliable measure for identifying single-layer graphene.
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78.66.Sq Composite materials
78.30.Hv Other nonmetallic inorganics
81.05.U- Carbon/carbon-based materials

Optical transitions in polarized CdSe, CdSe/ZnSe, and CdSe/CdS/ZnS quantum dots dispersed in various polar solvents

Ung Thi Dieu Thuy, Nguyen Quang Liem, Do Xuan Thanh, Myriam Protière, and Peter Reiss

Appl. Phys. Lett. 91, 241908 (2007); http://dx.doi.org/10.1063/1.2822399 (3 pages) | Cited 5 times

Online Publication Date: 12 December 2007

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The optical transitions in ensembles of colloidal CdSe-based quantum dots (QDs) have been systematically studied as a function of the net QDs’ polarity/polarization and of the solvent’s polarity. While the general trend observed for all QD systems dispersed in different solvents is similar, the spectral shifts are more pronounced in core QDs than in core/shell structures. Our results can be rationalized by taking account of the electric field experienced by the QDs that results from their effective polarization in solvents of different polarities (quantum confined Stark effect) as well as from the effect of the external dielectric environment (solvatochromatic effect).
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78.67.Hc Quantum dots
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Control of valence band states in pyramidal quantum dot-in-dot semiconductor heterostructures

V. Troncale, K. F. Karlsson, E. Pelucchi, A. Rudra, and E. Kapon

Appl. Phys. Lett. 91, 241909 (2007); http://dx.doi.org/10.1063/1.2820693 (3 pages) | Cited 4 times

Online Publication Date: 12 December 2007

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The character of the hole states in a pyramidal GaAs/AlGaAs quantum dot-in-dot (DiD) heterostructure is shown to be controllable by tailoring the confinement potential shape. The change in ground valence band state from heavy hole like to light hole like is demonstrated by side-view polarization resolved photoluminescence measurements. The experimental findings are supported by three-dimensional numerical model calculations. The results are applicable for polarization control in quantum dot photonic devices.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
73.21.La Quantum dots
81.07.Ta Quantum dots

Molecular dynamics simulation of interfacial thermal conductance between silicon and amorphous polyethylene

Ming Hu, Sergei Shenogin, and Pawel Keblinski

Appl. Phys. Lett. 91, 241910 (2007); http://dx.doi.org/10.1063/1.2824864 (3 pages) | Cited 11 times

Online Publication Date: 12 December 2007

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Using nonequilibrium molecular dynamics simulations, we study the interfacial thermal conductance between single crystal silicon and amorphous polyethylene (PE). We estimate that the silicon-PE interfacial thermal conductance is about 20 MW/m2 K at room temperature, which is equivalent to the resistance of 16 nm thick layer of bulk amorphous polyethylene. We also study the role of solid stiffness and the bonding strength across the interface on the interfacial thermal resistance. With strong interfacial bonding, our results are in agreement with the diffuse mismatch model and phonon radiation limit predictions, suggesting that in this case, heat carrying acoustic phonons in solids have transmission coefficients to polymer equal almost to unity.
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65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
73.40.Mr Semiconductor-electrolyte contacts

Temperature stability of ZnO:Al film properties for poly-Si thin-film devices

K. Y. Lee, C. Becker, M. Muske, F. Ruske, S. Gall, B. Rech, M. Berginski, and J. Hüpkes

Appl. Phys. Lett. 91, 241911 (2007); http://dx.doi.org/10.1063/1.2824456 (3 pages) | Cited 14 times

Online Publication Date: 14 December 2007

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The crystallization of thin silicon films at temperatures between 425 and 600 °C was investigated on glass substrates coated with Al-doped zinc oxide (ZnO:Al). Bare ZnO:Al layers degrade at the crystallization temperatures used. A silicon layer on top, however, efficiently prevents deterioration. The resistivity was even found to drop from 4.3×10−4 Ω cm for the as deposited ZnO:Al to 2.2×10−4 Ω cm in the case of aluminium induced crystallization and to 3.4×10−4 Ω cm for solid phase crystallization. The temperature-stable conductivity of ZnO:Al films coated with Si opens up appealing options for the production of polycrystalline silicon thin-film solar cells with transparent front contacts.
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73.61.Ga II-VI semiconductors
84.60.Jt Photoelectric conversion
64.70.K- Solid-solid transitions
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