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30 Nov 2009

Volume 95, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 223701 (2009); http://dx.doi.org/10.1063/1.3240400 (3 pages)

Yaling Liu and Samir M. Iqbal
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Extending the nanocluster-Si/erbium sensitization distance in Er-doped silicon nitride: The role of Er–Er energy migration

In Yong Kim, Jung H. Shin, and Kyung Joong Kim

Appl. Phys. Lett. 95, 221101 (2009); http://dx.doi.org/10.1063/1.3259723 (3 pages) | Cited 8 times

Online Publication Date: 30 November 2009

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The nanocluster-Si (nc-Si)/Er3+ interaction distance in Er-doped silicon nitride is investigated using SiOx/Si3N4:Er/Si3N4/Si3N4:Er multilayers. The composition and thickness of SiOx layers were fixed to provide constant sensitization, while the thickness of Si3N4:Er layers was varied to probe distance-dependence of sensitization. We find that while the distance over which an nc-Si transfers energy to an Er3+ ion is constant at ∼ 0.3 nm, the effective sensitization distance over which an Er3+ is sensitized via nc-Si can be as large as ∼ 1.3 nm. Based on a widely used phenomenological model of the distance-dependent Er3+ photoluminescence intensity, we identify Er–Er energy migration as an important factor for the extension of the nc-Si sensitization distance over nc-Si energy transfer distance.
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61.46.-w Structure of nanoscale materials
61.72.up Other materials
68.65.Ac Multilayers
78.55.Hx Other solid inorganic materials

All-optical conditional logic with a nonlinear photonic crystal nanocavity

Murray W. McCutcheon, Georg W. Rieger, Jeff F. Young, Dan Dalacu, Philip J. Poole, and Robin L. Williams

Appl. Phys. Lett. 95, 221102 (2009); http://dx.doi.org/10.1063/1.3265736 (3 pages) | Cited 7 times

Online Publication Date: 30 November 2009

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We demonstrate tunable frequency-converted light mediated by a χ(2) nonlinear photonic crystal nanocavity. The InP-based cavity supports two closely spaced localized modes near 1550 nm, which are resonantly excited by a 130 fs laser pulse. The cavity is simultaneously irradiated with a nonresonant probe beam, giving rise to rich second-order scattering spectra showing nonlinear mixing of the different resonant and nonresonant components. We highlight the radiation at the sum frequencies of the probe beam and the respective cavity modes. This would be a useful, minimally invasive monitor of the joint occupancy state of multiple cavities in an integrated optical circuit.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.70.Qs Photonic bandgap materials
42.82.-m Integrated optics

Realization of a single and closed Λ-system in a room-temperature three-level coherently prepared resonant medium with narrow D1 hyperfine splittings

K. Li, L. Deng, and M. G. Payne

Appl. Phys. Lett. 95, 221103 (2009); http://dx.doi.org/10.1063/1.3269997 (3 pages) | Cited 2 times

Online Publication Date: 1 December 2009

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A single, closed three-state Λ-system in room-temperature rubidium is investigated experimentally using a copropagating beam parallel-polarization configuration under weakly driven electromagnetically induced transparency (EIT) condition. Compare with the widely used orthogonal-polarization beam EIT configuration where multiple nonclosed Λ-schemes coexist, the parallel-polarizations configuration can completely eliminate the leakage light from the control field. Our state preparation and laser polarization lead to a single and closed Λ-scheme that eliminates the detrimental absorption due to nearby states in atomic species with hyperfine separations smaller than Doppler-broadened line widths, a case where the conventional EIT configuration fails completely.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
32.70.Jz Line shapes, widths, and shifts
31.30.Gs Hyperfine interactions and isotope effects
32.80.-t Photoionization and excitation

High power broad area quantum cascade lasers

Y. Bai, S. Slivken, S. R. Darvish, A. Haddadi, B. Gokden, and M. Razeghi

Appl. Phys. Lett. 95, 221104 (2009); http://dx.doi.org/10.1063/1.3270043 (3 pages) | Cited 19 times

Online Publication Date: 1 December 2009

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Broad area quantum cascade lasers (QCLs) are studied with ridge widths up to 400 μm, in room temperature pulsed mode operation at an emission wavelength around 4.45 μm. The peak output power scales linearly with the ridge width. A maximum total peak output power of 120 W is obtained from a single 400-μm-wide device with a cavity length of 3 mm. A stable far field emission characteristic is observed with dual lobes at ±38° for all tested devices, which suggests that these broad area QCLs are highly resistant to filamentation.
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42.55.Px Semiconductor lasers; laser diodes

Optical waveguide and cavity effects on whispering-gallery mode resonances in a ZnO nanonail

Jinzhang Liu, Quang Minh Ngo, Kyung Ho Park, Sangin Kim, Yeong Hwan Ahn, Ji-Yong Park, Ken Ha Koh, and Soonil Lee

Appl. Phys. Lett. 95, 221105 (2009); http://dx.doi.org/10.1063/1.3268806 (3 pages) | Cited 10 times

Online Publication Date: 2 December 2009

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Spatially resolved cathodoluminescence (CL) study of a ZnO nanonail, having thin shank, tapered neck, and hexagonal head sections, is reported. Monochromatic imaging and line-scan profiling indicate that the wave guiding and leaking from growth imperfections in addition to the oxygen-deficiency variation determine the spatial contrast of CL emissions. Occurrence of resonance peaks at identical wavelengths regardless of CL-excitation spots is inconsistent with the whispering-gallery mode (WGM) resonances of a two-dimensional cavity in the finite-difference time domain simulation. However, three-dimensioanl cavity simulation produced WGM peaks that are consistent with the experimental spectra, including transverse-electric resonances that are comparable to transverse-magnetic ones.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Enhancement in ultraviolet optoelectronic performance of photoconductive semiconductor switch based on ZnO nanobelts film

X. J. Zheng, B. Yang, T. Zhang, C. B. Jiang, S. X. Mao, Y. Q. Chen, and B. Yuan

Appl. Phys. Lett. 95, 221106 (2009); http://dx.doi.org/10.1063/1.3258462 (3 pages) | Cited 8 times

Online Publication Date: 2 December 2009

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Photoconductive semiconductor switches (PCSSs) based on ZnO nanobelts film and ZnO thin film were fabricated and applied into a test circuit to control the circuit state. The photosensitivity, leakage current from I-V characteristics, and the “on-off” voltage ratio from voltage spectrums of the former are 102 times higher, ten times lower, and two times higher than that of the latter, respectively. It indicates that PCSS based on ZnO nanobelts film has larger photoresponse, better “off state,” and more effective switching function, and they are regarded as consequences of longer transport path and higher surface to volume ratio according to oxygen chemisorption mechanism.
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85.60.-q Optoelectronic devices
68.55.ag Semiconductors
68.43.Mn Adsorption kinetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Engineering the band gap of carbon nanotube for infrared sensors

King Wai Chiu Lai, Ning Xi, Carmen Kar Man Fung, Hongzhi Chen, and Tzyh-Jong Tarn

Appl. Phys. Lett. 95, 221107 (2009); http://dx.doi.org/10.1063/1.3269636 (3 pages) | Cited 4 times

Online Publication Date: 2 December 2009

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Carbon nanotube (CNT) has been found to be one of the promising semiconducting materials for nanoelectronic sensors due to its unique electrical properties. Our group has developed a spectrum sensor using a single CNT and demonstrated its performance. In this paper, a steady and high-yield CNT band gap engineering will be developed and used to manufacture an appropriate CNT for infrared (IR) detection. The fabrication and experimental result of the CNT-based spectrum sensor will be presented. The results indicate that the CNT-based spectrum sensor is capable to sense near IR and middle-wave IR signals at room temperature.
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85.35.Kt Nanotube devices
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.07.De Nanotubes
81.05.Cy Elemental semiconductors
73.22.-f Electronic structure of nanoscale materials and related systems
85.60.Gz Photodetectors (including infrared and CCD detectors)

High quality GaInP nonlinear photonic crystals with minimized nonlinear absorption

Sylvain Combrié, Quynh Vy Tran, Alfredo De Rossi, Chad Husko, and Pierre Colman

Appl. Phys. Lett. 95, 221108 (2009); http://dx.doi.org/10.1063/1.3269998 (3 pages) | Cited 15 times

Online Publication Date: 2 December 2009

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We have established a new material, indium gallium phosphide, lattice matched to gallium arsenide, for two-dimensional photonic crystals at 1.55 μm. We have demonstrated single-mode cavities with intrinsic Q-factor larger than one million and achieved very large self-phase-modulation coefficient 1.1×103 W1 m−1 in line-defect waveguides. Importantly, the material band gap is such that two-photon absorption, Eg>2ℏω, is completely suppressed at this important telecommunications wavelength.
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42.70.Qs Photonic bandgap materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Nr Semiconductor compounds
42.65.Wi Nonlinear waveguides

Coupling of light from an optical fiber taper into silver nanowires

Chun-Hua Dong, Xi-Feng Ren, Rui Yang, Jun-Yuan Duan, Jian-Guo Guan, Guang-Can Guo, and Guo-Ping Guo

Appl. Phys. Lett. 95, 221109 (2009); http://dx.doi.org/10.1063/1.3270530 (3 pages) | Cited 12 times

Online Publication Date: 3 December 2009

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We report the coupling of photons from an optical fiber taper to surface plasmon modes of silver nanowires. The coupling efficiency can be modulated by adjusting the cross angle and the polarization of the input light. The launch of propagating plasmons can be realized not only at ends of the nanowires but also at the midsection. In addition, we present the coupling of light into multiple nanowires from a single optical fiber taper simultaneously. Our demonstration offers an efficient method for optimizing plasmon coupling into nanoscale metallic waveguides and promotes the realization of highly integrated plasmonic devices.
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42.81.Qb Fiber waveguides, couplers, and arrays
42.82.Et Waveguides, couplers, and arrays
78.67.Uh Nanowires
78.68.+m Optical properties of surfaces
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations

Impact of two-floor air prism arrays as an embedded reflector for enhancing the output power of InGaN/GaN light emitting diodes

Hyung Gu Kim, Hyun Kyu Kim, Hee Yun Kim, Jae Hyoung Ryu, Ji Hye Kang, Nam Han, Periyayya Uthirakumar, and Chang-Hee Hong

Appl. Phys. Lett. 95, 221110 (2009); http://dx.doi.org/10.1063/1.3270534 (3 pages) | Cited 9 times

Online Publication Date: 3 December 2009

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This paper reports on the impact of two-floor air prism (TFAP) arrays InGaN/GaN light emitting diodes (LEDs) as an embedded reflector with low refractive indices. The reflectance spectra, measured over the entire visible spectral region, shows strong reflectance modulations due to the TFAP arrays in GaN. The light output powers of TFAP LEDs is seen to be 2.62 times higher than that of conventional LEDs, and 1.55 times higher than that of LEDs with one floor air prism arrays, respectively, at injection currents of 100 mA. This significant enhancement is attributable to a combined effect of effective shaping with 62° angled sidewalls and high refractive index difference between the embedded air prism and the GaN.
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85.60.Jb Light-emitting devices
78.40.Fy Semiconductors
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Emission of terahertz radiations from fractal antennas

F. Miyamaru, Y. Saito, M. W. Takeda, L. Liu, B. Hou, W. Wen, and Ping Sheng

Appl. Phys. Lett. 95, 221111 (2009); http://dx.doi.org/10.1063/1.3271181 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2009

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We investigate the emission of terahertz radiation from a photoconductive fractal antenna fabricated on a semi-insulating gallium arsenide substrate. Owing to the self-similarity of fractal structures, our fractal antenna shows a multiband emission of terahertz radiation. The emission intensity at peak frequency is about twice that from a bow-tie antenna. We also investigate the mechanism of the multiband emission by using the finite-difference time-domain calculation.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
05.45.Df Fractals
84.40.Ba Antennas: theory, components and accessories

Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer gain length

G. F. Benavides, J. W. Zimmerman, B. S. Woodard, D. L. Carroll, A. D. Palla, M. T. Day, J. T. Verdeyen, and W. C. Solomon

Appl. Phys. Lett. 95, 221112 (2009); http://dx.doi.org/10.1063/1.3269811 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2009

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Herein the authors report on the demonstration of a 95% enhancement in continuous-wave laser power on the 1315 nm transition of atomic iodine via a 50% increase in gain length, flow rates, and discharge power. O2(a 1Δ) is produced by a single radio-frequency-excited electric discharge sustained in an O2–He–NO gas mixture flowing through a rectangular geometry, and I(2P1/2) is then pumped using energy transferred from O2(a 1Δ). A gain of 0.26% cm−1 was obtained and the total laser output power was 54.8 W.
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42.55.Ks Chemical lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Two-photon excited fluorescence from CdSe quantum dots on SiN photonic crystals

Xingsheng Xu, Toshiki Yamada, Rieko Ueda, and Akira Otomo

Appl. Phys. Lett. 95, 221113 (2009); http://dx.doi.org/10.1063/1.3270525 (3 pages) | Cited 4 times

Online Publication Date: 4 December 2009

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Two-photon excited fluorescence from CdSe quantum dots on a two-dimensional SiN photonic crystal surface is investigated by using a femtosecond laser. By using a photonic crystal, a 90-fold enhancement in the two-photon excited fluorescence in the vertical direction is achieved. This is the highest enhancement achieved so far in the two-photon excited fluorescence in the vertical direction. The mechanism of the enhancement for two-photon excited fluorescence from quantum dots on photonic crystals is analyzed.
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78.67.Hc Quantum dots
81.07.Ta Quantum dots
78.55.Et II-VI semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.47.J- Ultrafast spectroscopy (<1 psec)

Fabrication of controlled volume scattering medium in poly(methyl methacrylate) by focused femtosecond laser pulses

Osamu Matoba, Yuri Kitamura, Tomoyuki Manabe, Kouichi Nitta, and Wataru Watanabe

Appl. Phys. Lett. 95, 221114 (2009); http://dx.doi.org/10.1063/1.3268452 (3 pages) | Cited 2 times

Online Publication Date: 4 December 2009

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A volume scattering medium was fabricated in a transparent material by focused femtosecond laser pulses. A random distribution of voids fabricated by femotosecond pulsed laser light acted as a volume scattering medium that may be applied to photonic secure data storage. We fabricated a partially random distribution of voids in poly(methyl methacrylate) and then measured the scattering properties. Comparing beam widths of the output intensity distribution through the scattering medium, obtained from both complex amplitude propagation and Monte Carlo simulation, showed that the scattering coefficient can be controlled by the void density.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Jk Polymers and organics
42.25.Fx Diffraction and scattering

Time-resolved studies of a rolled-up semiconductor microtube laser

Ch. Strelow, M. Sauer, S. Fehringer, T. Korn, C. Schüller, A. Stemmann, Ch. Heyn, D. Heitmann, and T. Kipp

Appl. Phys. Lett. 95, 221115 (2009); http://dx.doi.org/10.1063/1.3271176 (3 pages) | Cited 8 times

Online Publication Date: 4 December 2009

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We report on lasing in rolled-up microtube resonators. Time-resolved studies on these semiconductor lasers containing GaAs quantum wells as optical gain material reveal particularly fast turn-on times and short pulse emissions above the threshold. We observe a strong redshift of the laser mode during the pulse emission which is compared to the time evolution of the charge-carrier density calculated by rate equations.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.70.-a Optical materials
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Control of polarization and dipole moment in low-dimensional semiconductor nanostructures

L. H. Li (李联合), M. Mexis, P. Ridha, M. Bozkurt, G. Patriarche, P. M. Smowton, P. Blood, P. M. Koenraad, and A. Fiore

Appl. Phys. Lett. 95, 221116 (2009); http://dx.doi.org/10.1063/1.3269592 (3 pages) | Cited 3 times

Online Publication Date: 4 December 2009

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We demonstrate the control of polarization and dipole moment in semiconductor nanostructures, through nanoscale engineering of shape and composition. Rodlike nanostructures, elongated along the growth direction, are obtained by molecular beam epitaxial growth. By varying the aspect ratio and compositional contrast between the rod and the surrounding matrix, we rotate the polarization of the dominant interband transition from transverse-electric to transverse-magnetic, and modify the dipole moment producing a radical change in the voltage dependence of absorption spectra. This opens the way to the optimization of quantum dot amplifiers and electro-optical modulators.
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78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.Jq Electro-optical effects
81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials
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Influence of spot size on extreme ultraviolet efficiency of laser-produced Sn plasmas

S. S. Harilal, R. W. Coons, P. Hough, and A. Hassanein

Appl. Phys. Lett. 95, 221501 (2009); http://dx.doi.org/10.1063/1.3270526 (3 pages) | Cited 17 times

Online Publication Date: 30 November 2009

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We have investigated the spot size effects on the extreme ultraviolet conversion efficiency (CE) of CO2 laser-produced Sn plasmas. The estimated CE of the laser to 13.5 nm radiation, within a 2% bandwidth, using a 10.6 μm CO2 laser with various pulse widths (25–55 ns) showed a double hump structure during a target-lens scan, where the CE is nearly 25% lower at the best focal position. Density analysis of the CO2 laser-produced plasma showed steep density gradients at the best focal position, and a reduction in CE at the best focal position, which is explained by the lack of efficient coupling between the laser and the plasma.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.-b Plasma properties

Intense ultrafast light kick by rotational Raman wake in atmosphere

Jian Wu, Hua Cai, Peifen Lu, Xueshi Bai, Liang’en Ding, and Heping Zeng

Appl. Phys. Lett. 95, 221502 (2009); http://dx.doi.org/10.1063/1.3266863 (3 pages) | Cited 10 times

Online Publication Date: 30 November 2009

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We report that intense ultrafast light can be particlelike kicked through the rotational Raman wake of the impulsively pre-excited diatomic molecules in atmosphere, manifested by controllable repulsion and attraction of intense pulses delayed by molecular alignment revival periods, and by mutual fusion of orthogonally polarized intense pulses nearby zero time delay. The rotational Raman wake facilitates longer ranges of interaction on the intense ultrafast light kicks than the plasma wake and Kerr effect.
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92.60.hk Convection, turbulence, and diffusion
92.60.hf Tropospheric composition and chemistry, constituent transport and chemistry
42.68.Bz Atmospheric turbulence effects
47.27.wb Turbulent wakes
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
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Diffuse and doubly split atom occupation in hexagonal LiBH4

Tamio Ikeshoji, Eiji Tsuchida, Kazutaka Ikeda, Motoaki Matsuo, Hai-Wen Li, Yoshiyuki Kawazoe, and Shin-ichi Orimo

Appl. Phys. Lett. 95, 221901 (2009); http://dx.doi.org/10.1063/1.3264953 (3 pages) | Cited 8 times

Online Publication Date: 30 November 2009

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A theoretical study has been performed to explain problems in the structural analysis of LiBH4 and its recently discovered superionic conductance. First-principles molecular dynamics simulations for the high temperature (hexagonal) phase show doubly split and diffuse occupation in the c-direction at Li and B sites, respectively. Li hopping within the split sites and libration of H atoms are also found. These dynamics are supported by the Rietveld analysis showing atomic displacement ellipsoids for Li and B atoms.
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63.20.dk First-principles theory
66.30.hd Ionic crystals

Dynamics of entrained air bubbles inside a piezodriven inkjet printhead

Sang Joon Lee, Dae Hee Kwon, and Yong Seok Choi

Appl. Phys. Lett. 95, 221902 (2009); http://dx.doi.org/10.1063/1.3268451 (3 pages) | Cited 1 time

Online Publication Date: 2 December 2009

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Entrained air bubbles inside a piezoelectric inkjet printhead cause a malfunction in the droplet formation and deteriorate the reliability of inkjet printing. The dynamic motion of the entrained air bubbles is investigated optically by utilizing a high-speed imaging system. Air bubbles, ingested through the inkjet nozzle, are surrounded by a pulsating pressure field inside the inkjet printhead. The bubbles oscillate and move along the inner wall of the printhead as they are subjected to the Bjerknes force. As the bubbles attract each other, they continuously coalesce and grow due to rectified diffusion until they reach the equilibrium condition.
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47.55.dd Bubble dynamics
47.55.df Breakup and coalescence
47.40.-x Compressible flows; shock waves

Electron spin relaxation by nuclei and holes in single InAs quantum dots

X. M. Dou, X. Y. Chang, B. Q. Sun, Y. H. Xiong, Z. C. Niu, H. Q. Ni, and D. S. Jiang

Appl. Phys. Lett. 95, 221903 (2009); http://dx.doi.org/10.1063/1.3270527 (3 pages)

Online Publication Date: 3 December 2009

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Electron spin relaxation of charged excitons X+ and X2+ are investigated by time-resolved and polarization-resolved photoluminescence spectroscopy. For X+ configuration, the electron spin relaxation shows a typical decay curve induced by hyperfine interaction with nuclei, whereas for X2+ state the electron spin relaxation is affected not only by nuclei but also by electron-hole exchange interaction, leading to a power-law time dependence.
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73.21.La Quantum dots
78.55.Cr III-V semiconductors
78.47.D- Time resolved spectroscopy (>1 psec)
71.70.Jp Nuclear states and interactions
72.25.Dc Spin polarized transport in semiconductors
78.67.Hc Quantum dots

X-ray excited luminescence of cuprous iodide single crystals: On the nature of red luminescence

Pan Gao, Mu Gu, Xiao-Lin Liu, Bo Liu, and Shi-Ming Huang

Appl. Phys. Lett. 95, 221904 (2009); http://dx.doi.org/10.1063/1.3271174 (3 pages) | Cited 6 times

Online Publication Date: 3 December 2009

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The x-ray excited luminescence spectra of different quality CuI crystals were measured. The prevailing blue luminescence and the unusual red luminescence were found at the same time. The relative intensity of these two luminescence peaks was different because of the change of defect concentration in crystals. By comparing the spectra of CuI crystals before and after annealing in vacuum, air or iodine vapors, the origin of the red luminescence in the as-grown crystals was ascribed to the presence of iodine vacancy, as confirmed by the energy dispersive x-ray analysis.
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78.55.Hx Other solid inorganic materials
61.72.jd Vacancies
61.72.Cc Kinetics of defect formation and annealing
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Surface adsorption and disordering in LiFePO4 based battery cathodes

Archana Kayyar, Haijun Qian, and Jian Luo

Appl. Phys. Lett. 95, 221905 (2009); http://dx.doi.org/10.1063/1.3270106 (3 pages) | Cited 7 times

Online Publication Date: 3 December 2009

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A recent study [ Kang and Ceder, Nature (London) 458, 190 (2009) ] suggested that a Li4P2O7-like “fast ion-conducting surface phase” could form on the surfaces of LiFePO4 particles, enabling ultrafast discharging of Li-ion batteries. We demonstrate that these nanoscale surface films exhibit a self-selecting or “equilibrium” thickness, akin to those observed in simpler binary oxides [ Luo and Chiang, Annu. Rev. Mater. Res. 38, 227 (2008) ]. These observations can be interpreted as a case of coupled prewetting and premelting. Similar nanoscale intergranular films are also observed. These nanoscale interfacial phenomena can be utilized to tailor nanoparticles for battery and many other applications.
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82.47.Aa Lithium-ion batteries
82.45.Fk Electrodes
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Nonlinear refractive index and three-photon absorption coefficient of poly(9,9-dioctylfluorence)

J. I. Jang, S. Mani, J. B. Ketterson, P. Lovera, and G. Redmond

Appl. Phys. Lett. 95, 221906 (2009); http://dx.doi.org/10.1063/1.3269588 (3 pages) | Cited 2 times

Online Publication Date: 4 December 2009

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We investigate the optical Kerr effect and third harmonic generation (THG) arising from χ(3) of poly(9,9-dioctylfluorence), which is an emerging organic π-conjugated polymer from the perspective of diverse optoelectronic applications. The measured nonlinear refractive index, obtained with closed-aperture Z-scan, is n2 = (2.04±0.10)×10−12 esu at λ = 1540 nm. Open-aperture Z-scan yields the three-photon absorption coefficient of γ = (1.88±0.26)×10−3 cm3/GW2 at λ = 1064 nm, arising from χ(5) response. The wavelength-dependent THG indicates that this semiconducting polymer can be a potentially useful polymer system for nonlinear-optics applications involving high-order optical processes in the mid-IR range.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
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Calculation of Cu/Ta interface electron transmission and effect on conductivity in nanoscale interconnect technology

Baruch Feldman and Scott T. Dunham

Appl. Phys. Lett. 95, 222101 (2009); http://dx.doi.org/10.1063/1.3257700 (3 pages) | Cited 4 times

Online Publication Date: 30 November 2009

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Resistivity augmentation in nanoscale metal interconnects is a performance limiting factor in integrated circuits. Here we present calculations of electron scattering and transmission at the interface between Cu interconnects and their barrier layers, in this case Ta. We also present a semiclassical model to predict the technological impact of this scattering and find that a barrier layer can significantly decrease conductivity, consistent with previously published measurements.
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85.40.Ls Metallization, contacts, interconnects; device isolation
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