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5 Mar 2012

Volume 100, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 101903 (2012); http://dx.doi.org/10.1063/1.3673327 (3 pages)

Michael Ian Lapsley, Anaram Shahravan, Qingzhen Hao, Bala Krishna Juluri, Stephen Giardinelli, Mengqian Lu, Yanhui Zhao, I-Kao Chiang, Themis Matsoukas, and Tony Jun Huang
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Multicolor Čerenkov conical beams generation by cascaded-χ(2) processes in radially poled nonlinear photonic crystals

H. X. Li, S. Y. Mu, P. Xu, M. L. Zhong, C. D. Chen, X. P. Hu, W. N. Cui, and S. N. Zhu

Appl. Phys. Lett. 100, 101101 (2012); http://dx.doi.org/10.1063/1.3692593 (4 pages) | Cited 4 times

Online Publication Date: 5 March 2012

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We observe multiple simultaneous cascaded-χ(2) Čerenkov conical radiations in radially poled nonlinear photonic crystals. By using two incident fundamental waves ω1 and ω2, a variety of cascaded nonlinear up-conversion processes occur which result in high-frequency Čerenkov radiations at 2ωi+ωj(i,j = 1,2) exhibiting as multicolor conical beams. Two types of phase-matching geometries with different emission angles are demonstrated for each kind of cascaded-χ(2) Čerenkov radiation. The external angle of the Čerenkov radiation exhibits strong dependence on the fundamental wavelengths. The experimental results agree well with the theoretical calculations.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.70.Qs Photonic bandgap materials
42.65.-k Nonlinear optics

Ultrafast laser inscribed waveguide lattice in glass for direct observation of transverse localization of light

Somnath Ghosh, Nicholas D. Psaila, R. R. Thomson, Bishnu P. Pal, R. K. Varshney, and Ajoy K. Kar

Appl. Phys. Lett. 100, 101102 (2012); http://dx.doi.org/10.1063/1.3691194 (4 pages) | Cited 3 times

Online Publication Date: 5 March 2012

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We present initial results of the direct observation of the signature of localized light in an ultrafast laser-inscribed (ULI) disordered lattice that contains an array of evanescently coupled, one-dimensional optical waveguides in glass in which certain amount of disorder in refractive index was introduced. Numerical simulations were carried out to test the feasibility of the initial experimental design. Such configurable ULI disordered waveguide lattices should open up a platform for investigating the phenomenon of transverse localization of light and its statistical nature.
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42.62.-b Laser applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.Ce Glasses, quartz
42.79.Gn Optical waveguides and couplers

Assembly of microparticles by optical trapping with a photonic crystal nanocavity

C. Renaut, J. Dellinger, B. Cluzel, T. Honegger, D. Peyrade, E. Picard, F. de Fornel, and E. Hadji

Appl. Phys. Lett. 100, 101103 (2012); http://dx.doi.org/10.1063/1.3692104 (3 pages) | Cited 5 times

Online Publication Date: 5 March 2012

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multimedia

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In this work, we report the auto-assembly experiments of micrometer sized particles by optical trapping in the evanescent field of a photonic crystal nanocavity. The nanocavity is inserted inside an optofluidic cell designed to enable the real time control of the nanoresonator transmittance as well as the real time visualization of the particles motion in the vicinity of the nanocavity. It is demonstrated that the optical trap above the cavity enables the assembly of multiple particles in respect of different stable conformations.
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42.50.Wk Mechanical effects of light on material media, microstructures and particles
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Qs Photonic bandgap materials
81.16.Dn Self-assembly

Air-guided photonic-crystal-fiber pulse-compression delivery of multimegawatt femtosecond laser output for nonlinear-optical imaging and neurosurgery

Aleksandr A. Lanin, Il’ya V. Fedotov, Dmitrii A. Sidorov-Biryukov, Lyubov V. Doronina-Amitonova, Olga I. Ivashkina, Marina A. Zots, Chi-Kuang Sun, F. Ömer Ilday, Andrei B. Fedotov, Konstantin V. Anokhin, and Aleksei M. Zheltikov

Appl. Phys. Lett. 100, 101104 (2012); http://dx.doi.org/10.1063/1.3681777 (4 pages) | Cited 2 times

Online Publication Date: 6 March 2012

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Large-core hollow photonic-crystal fibers (PCFs) are shown to enable a fiber-format air-guided delivery of ultrashort infrared laser pulses for neurosurgery and nonlinear-optical imaging. With an appropriate dispersion precompensation, an anomalously dispersive 15-μm-core hollow PCF compresses 510-fs, 1070-nm light pulses to a pulse width of about 110 fs, providing a peak power in excess of 5 MW. The compressed PCF output is employed to induce a local photodisruption of corpus callosum tissues in mouse brain and is used to generate the third harmonic in brain tissues, which is captured by the PCF and delivered to a detector through the PCF cladding.
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87.19.lh Optical imaging of neuronal activity
42.62.Be Biological and medical applications
87.63.lt Laser imaging
42.55.Tv Photonic crystal lasers and coherent effects

Control of coherent acoustic phonon generation with external bias in InGaN/GaN multiple quantum wells

C. S. Kim, J. H. Kim, H. Jeong, Y. D. Jho, H. K. Kwon, H. S. Lee, J. S. Park, K. Song, S. H. Kim, Y. J. Kim, D. Lee, and K. J. Yee

Appl. Phys. Lett. 100, 101105 (2012); http://dx.doi.org/10.1063/1.3692594 (3 pages)

Online Publication Date: 6 March 2012

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Control of acoustic phonon generation with external bias is demonstrated for an InGaN light-emitting diode by performing femtosecond pump–probe measurements. The evolution of both the carrier dynamics and the acoustic phonon strength with an external bias reveals that the acoustic wave is generated during the carrier sweeping process of the depletion field, where electric field screening accompanies stress of the lattice for a piezoelectric material.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
62.65.+k Acoustical properties of solids

Towards all-dielectric, polarization-independent optical cloaks

Jacob Andkjær, N. Asger Mortensen, and Ole Sigmund

Appl. Phys. Lett. 100, 101106 (2012); http://dx.doi.org/10.1063/1.3691835 (3 pages) | Cited 1 time

Online Publication Date: 6 March 2012

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Fully enclosing, all-dielectric cloaks working for both Ez and Hz polarizations simultaneously are presented in this letter. The cloaks are effective for two antiparallel angles of incidence, and the layout of standard dielectric material in the cloak is determined by topology optimization. Scattering from cylinder and cloak is reduced for an Hz-polarized wave compared to an Ez-polarized wave by taking advantage of the surface mode at the perfectly electric conducting boundary. Perhaps contrary to simple intuition, fully enclosed, all-dielectric, low-contrast cloaks cannot be designed effectively when distributing a material with lower permittivity than the background material.
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42.70.-a Optical materials

Surface wave resonances supported on a square array of square metallic pillars

S. J. Berry, T. Campbell, A. P. Hibbins, and J. R. Sambles

Appl. Phys. Lett. 100, 101107 (2012); http://dx.doi.org/10.1063/1.3691949 (3 pages) | Cited 2 times

Online Publication Date: 6 March 2012

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A family of transverse-magnetic surface waves is shown to be supported at microwave frequencies by a square array of subwavelength square cross-section metal pillars on a conducting ground plane. These surface waves are experimentally characterised with a collimated microwave beam apparatus that utilises a pair of two-dimensional parabolic mirrors positioned on the sample surface. The dispersion of the modes, each associated with a quantisation of the electromagnetic field in the depth of the slits, is fully characterised and compared with the predictions of finite element modelling.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
75.70.Rf Surface magnetism
78.70.Gq Microwave and radio-frequency interactions

Measurement of light diffusion in ZnO nanowire forests

Marijn A. M. Versteegh, Ruben E. C. van der Wel, and Jaap I. Dijkhuis

Appl. Phys. Lett. 100, 101108 (2012); http://dx.doi.org/10.1063/1.3692741 (4 pages) | Cited 2 times

Online Publication Date: 8 March 2012

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Optimum design of efficient nanowire solar cells requires better understanding of light diffusion in a nanowire array. Here we demonstrate that our recently developed ultrafast all-optical shutter can be used to directly measure the dwell time of light in a nanowire array. Our measurements on disordered ZnO nanowire arrays, “nanowire forests,” indicate that the photon mean free path and the dwell time of light can be well predicted from SEM images.
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78.66.Hf II-VI semiconductors
78.40.Fy Semiconductors
78.47.J- Ultrafast spectroscopy (<1 psec)

Tapered gold-helix metamaterials as improved circular polarizers

Justyna K. Gansel, Michael Latzel, Andreas Frölich, Johannes Kaschke, Michael Thiel, and Martin Wegener

Appl. Phys. Lett. 100, 101109 (2012); http://dx.doi.org/10.1063/1.3693181 (3 pages) | Cited 6 times

Online Publication Date: 8 March 2012

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We have previously shown that square arrays of three-dimensional gold helices can serve as compact broadband circular polarizers. Here, we show by heuristic reasoning supported by numerical calculations that the bandwidth of the device can realistically be increased to 1.5 octaves by tapering the gold-helix radius. The tapering also improves the extinction ratio. Depending on the side from which light impinges onto the tapered helices, the polarization conversions are different. Therefore, the structure is either optimal as polarizer or as analyzer. Corresponding structures for the infrared spectral range are fabricated by direct laser writing and gold electroplating.
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42.70.-a Optical materials
42.79.Ci Filters, zone plates, and polarizers
42.86.+b Optical workshop techniques
42.62.Cf Industrial applications

Polarization insensitive in-fiber mode-locker based on carbon nanotube with N-methyl-2-pryrrolidone solvent filled fiber microchamber

Chengbo Mou, Aleksey G. Rozhin, Raz Arif, Kaiming Zhou, and Sergei Turitsyn

Appl. Phys. Lett. 100, 101110 (2012); http://dx.doi.org/10.1063/1.3691922 (4 pages)

Online Publication Date: 8 March 2012

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We report an in-fiber laser mode locker based on carbon nanotube with n-methyl-2-pryrrolidone solvent filled in-fiber microchamber. Symmetrically femtosecond laser fabricated in-fiber microchamber with randomly oriented nanotubes assures polarization insensitive oscillation of laser mode locking. The proposed and demonstrated passively mode locked fiber laser shows higher energy soliton output. The laser has an output power of ∼29 mW (corresponding to 11 nJ energy). It shows stable soliton output with a repetition rate of ∼2.3 MHz and pulse width of ∼3.37 ps.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.81.Gs Birefringence, polarization
42.81.Bm Fabrication, cladding, and splicing
42.65.Tg Optical solitons; nonlinear guided waves

Stimulated supercontinuum generation extends broadening limits in silicon

P. T. S. DeVore, D. R. Solli, C. Ropers, P. Koonath, and B. Jalali

Appl. Phys. Lett. 100, 101111 (2012); http://dx.doi.org/10.1063/1.3692103 (4 pages) | Cited 1 time

Online Publication Date: 8 March 2012

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We demonstrate that stimulated supercontinuum generation alleviates restrictions on spectral broadening in silicon waveguides. At telecommunications wavelengths, two-photon and free-carrier absorption typically deplete the pump before large broadening factors can be achieved. However, broadening via modulation instability (MI) can be enhanced by seeding, which also substantially improves the energy efficiency of spectral broadening in media with nonlinear loss. Coherent seeding also generates a stable output spectrum, in contrast to conventional approaches where broadening starts from noise. The combination of self-phase modulation and stimulated modulation instability generates broadening factors in excess of 40-fold at moderate intensity levels, with >15-times better energy efficiency.
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42.79.Gn Optical waveguides and couplers
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Dominant ultraviolet electroluminescence from p-ZnO:As/n-SiC(6H) heterojunction light-emitting diodes

Zhifeng Shi, Xiaochuan Xia, Wei Yin, Shikai Zhang, Hui Wang, Jin Wang, Long Zhao, Xin Dong, Baolin Zhang, and Guotong Du

Appl. Phys. Lett. 100, 101112 (2012); http://dx.doi.org/10.1063/1.3694025 (4 pages) | Cited 2 times

Online Publication Date: 9 March 2012

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Ultraviolet electroluminescence was demonstrated from a p-ZnO:As/n-SiC(6H) heterojunction light-emitting diode at room-temperature. The p-ZnO:As was fabricated by out-diffusion of arsenic atoms from a sandwiched GaAs interlayer on SiC substrate. The p-type doping was confirmed by both Hall and low-temperature photoluminescence measurements. Under forward bias, an intense ultraviolet emission centered at 384 nm was achieved from ZnO side of the diode. Furthermore, the light-output-current characteristic was determined to evaluate the high-efficiency electroluminescence performance of the diode.
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85.60.Jb Light-emitting devices
85.30.Kk Junction diodes
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Surface functionalization of 6H-SiC using organophosphonate monolayers

M. Auernhammer, S. J. Schoell, M. Sachsenhauser, K.-C. Liao, J. Schwartz, I. D. Sharp, and A. Cattani-Scholz

Appl. Phys. Lett. 100, 101601 (2012); http://dx.doi.org/10.1063/1.3691919 (4 pages)

Online Publication Date: 5 March 2012

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The synthesis and characterization of self-assembled monolayers prepared from 11-hydroxyundecyphosphonic acid and 9,10-diphenyl-2,6-diphosphonoanthracene on n-type 6H-SiC is described. Structural and chemical properties of these monolayers were investigated through contact angle measurements, atomic force microscopy, x-ray photoelectron spectroscopy, and Fourier transformation infrared spectroscopy, which indicate covalent bonding of the phosphonates to both (0001)- and (000-1)-oriented 6H-SiC crystal faces. Electrical characterization was achieved through contact potential difference and surface photovoltage measurements, which revealed significant changes in the work functions of the substrates by monolayer formation.
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81.65.-b Surface treatments
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
68.37.Ps Atomic force microscopy (AFM)
72.40.+w Photoconduction and photovoltaic effects
72.80.Jc Other crystalline inorganic semiconductors
73.25.+i Surface conductivity and carrier phenomena

Interfacial stabilization of bilayered nanolaminates by asymmetric block copolymers

Arif O. Gozen, Jan Genzer, and Richard J. Spontak

Appl. Phys. Lett. 100, 101602 (2012); http://dx.doi.org/10.1063/1.3692102 (4 pages) | Cited 1 time

Online Publication Date: 6 March 2012

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Block copolymers are macromolecular surfactants that self-assemble into a variety of nanostructural elements or reduce the interfacial tension between incompatible polymers. Here, we examine the ability of diblock copolymers differing in composition to stabilize bilayered homopolymer nanolaminates on flat solid supports. In this arrangement, self-assembly competes with interfacial modification and, in one case, promotes destabilization of the top film. To discern the corresponding mechanism, we investigate nanolaminates with a thin copolymer layer positioned between the homopolymer layers. Stabilization commences when this middle layer is sufficiently thick so that the block that is miscible with the top layer forms a brush.
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81.16.Dn Self-assembly
61.46.-w Structure of nanoscale materials
68.55.am Polymers and organics

Metal-oxide-semiconductor field effect transistor humidity sensor using surface conductance

Seok-Ho Song, Hyun-Ho Yang, Chang-Hoon Han, Seung-Deok Ko, Seok-Hee Lee, and Jun-Bo Yoon

Appl. Phys. Lett. 100, 101603 (2012); http://dx.doi.org/10.1063/1.3691936 (3 pages)

Online Publication Date: 7 March 2012

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This letter presents a metal-oxide-semiconductor field effect transistor based humidity sensor which does not use any specific materials to sense the relative humidity. We simply make use of the low pressure chemical vapor deposited (LPCVD) silicon dioxide’s surface conductance change. When the gate is biased and then floated, the electrical charge in the gate is dissipated through the LPCVD silicon dioxide’s surface to the surrounding ground with a time constant depending on the surface conductance which, in turn, varies with humidity. With this method, extremely high sensitivity was achieved—the charge dissipation speed increased thousand times as the relative humidity increased.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
93.85.Jk Magnetic and electrical methods
85.30.Tv Field effect devices

Three-dimensional quantitative chemical roughness of buried ZrO2/In2O3 interfaces via energy-filtered electron tomography

X. Y. Zhong, B. Kabius, D. K. Schreiber, J. A. Eastman, D. D. Fong, and A. K. Petford-Long

Appl. Phys. Lett. 100, 101604 (2012); http://dx.doi.org/10.1063/1.3690861 (4 pages) | Cited 1 time

Online Publication Date: 9 March 2012

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The protocol to calculate the chemical roughness from three-dimensional (3-D) data cube acquired by energy-filtered electron tomography has been developed and applied to analyze the 3-D Zr distribution at the arbitrarily shaped interfaces in the ZrO2/In2O3 multilayer films. The calculated root-mean-square roughness quantitatively revealed the chemical roughness at the buried ZrO2/In2O3 interfaces, which is the deviation of Zr distribution from the ideal flat interface. Knowledge of the chemistry and structure of oxide interfaces in 3-D provides information useful for understanding changes in the behavior of a model ZrO2/In2O3 heterostructure that has potential to exhibit mixed conduction behavior.
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68.35.Ct Interface structure and roughness
72.60.+g Mixed conductivity and conductivity transitions
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Carbon isotope doping induced interfacial thermal resistance and thermal rectification in graphene

Qing-Xiang Pei, Yong-Wei Zhang, Zhen-Dong Sha, and Vivek B. Shenoy

Appl. Phys. Lett. 100, 101901 (2012); http://dx.doi.org/10.1063/1.3692173 (4 pages) | Cited 2 times

Online Publication Date: 5 March 2012

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We investigate the thermal transport properties of carbon isotope doped graphene using nonequilibrium molecular dynamics simulations. We find that the interfacial thermal resistance between graphene and the isotope atoms causes severe reduction in thermal conductivity of the doped graphene. Furthermore, we find that thermal rectification occurs in the interface. Tensile strain leads to an increase in the interfacial thermal resistance and thermal rectification, while increasing temperature decreases these parameters. We calculate the phonon spectra and find that the thermal rectification is associated with the overlap areas in the phonon spectra.
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66.70.Df Metals, alloys, and semiconductors
63.22.Rc Phonons in graphene

Electric-field-tuned color in photonic crystal elastomers

Qibin Zhao, Andrew Haines, David Snoswell, Christoph Keplinger, Rainer Kaltseis, Siegfried Bauer, Ingrid Graz, Richard Denk, Peter Spahn, Goetz Hellmann, and Jeremy J. Baumberg

Appl. Phys. Lett. 100, 101902 (2012); http://dx.doi.org/10.1063/1.3691930 (4 pages) | Cited 1 time

Online Publication Date: 5 March 2012

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Electrically tuned photonic crystals are produced by applying fields across shear-assembled elastomeric polymer opal thin films. At increasing voltages, the polymer opal films stretch biaxially under Maxwell stress, deforming the nanostructure and producing marked color changes. This quadratic electro-optic tuning of the photonic bandgap is repeatable over many cycles, switches within 100 ms, and bridges the gap between electro-active materials and photonic crystals.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.20.Jq Electro-optical effects
78.66.Qn Polymers; organic compounds
42.25.Bs Wave propagation, transmission and absorption

Shifts in plasmon resonance due to charging of a nanodisk array in argon plasma

Michael Ian Lapsley, Anaram Shahravan, Qingzhen Hao, Bala Krishna Juluri, Stephen Giardinelli, Mengqian Lu, Yanhui Zhao, I-Kao Chiang, Themis Matsoukas, and Tony Jun Huang

Appl. Phys. Lett. 100, 101903 (2012); http://dx.doi.org/10.1063/1.3673327 (3 pages) | Cited 2 times

Online Publication Date: 5 March 2012

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A method for generating charge-induced plasmonic shifts, using argon plasma to charge nanoparticle arrays, is presented. Particles develop a negative charge, due to enhanced collisions with high-temperature electrons, in low-temperature plasmas. The negative charge generated causes a blue shift in the localized surface plasmon resonance. The dynamics of the shift were recorded and discussed. This effect could be used as a real-time method for studying the dynamics for charging in plasma.
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73.22.Lp Collective excitations

Experimental observation of radial breathing-like mode of graphene nanoribbons

Fang Yu, Haiqing Zhou, Zengxing Zhang, Dongsheng Tang, Minjiang Chen, Huaichao Yang, Gang Wang, Haifang Yang, Changzhi Gu, and Lianfeng Sun

Appl. Phys. Lett. 100, 101904 (2012); http://dx.doi.org/10.1063/1.3692108 (4 pages) | Cited 3 times

Online Publication Date: 5 March 2012

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We report that single-walled carbon nanotubes (SWNTs) can be etched into graphene nanoribbons (GNRs) by iron etching, which is confirmed by Raman spectroscopy and transmission electron microscopy. Compared with SWNTs, there are some unique features in Raman spectra of GNRs: symmetric G peak with no splitting, larger Raman intensity of 2D peak than G peak, and lower frequency and narrower full width at half maximum for 2D peak. Similar to radial breathing modes in SWNTs, theoretically predicted radial breathing-like mode of GNRs is also observed: a clear and prominent peak around 223 cm−1 in the low frequency regions. This work paves the way for future studies of nanodevices based on SWNT-GNR heterojunction.
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78.30.Am Elemental semiconductors and insulators
81.05.ue Graphene
81.65.Cf Surface cleaning, etching, patterning

Effect of grain boundary on the buckling of graphene nanoribbons

M. Neek-Amal and F. M. Peeters

Appl. Phys. Lett. 100, 101905 (2012); http://dx.doi.org/10.1063/1.3692573 (4 pages)

Online Publication Date: 6 March 2012

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The buckling of graphene nano-ribbons containing a grain boundary is studied using atomistic simulations where free and supported boundary conditions are invoked. We consider the buckling transition of two kinds of grain boundaries with special symmetry. When graphene contains a large angle grain boundary with θ = 21.8°, the buckling strains are larger than those of perfect graphene when the ribbons with free (supported) boundary condition are subjected to compressive tension parallel (perpendicular) to the grain boundary. This is opposite for the results of θ = 32.2°. The shape of the deformations of the buckled graphene nanoribbons depends on the boundary conditions, the presence of the particular used grain boundaries, and the direction of applied in-plane compressive tension.
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61.72.Mm Grain and twin boundaries
61.48.Gh Structure of graphene
62.20.mq Buckling
81.40.Lm Deformation, plasticity, and creep
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Near-infrared photoluminescence from ZnO

Mingsong Wang, Yajun Zhou, Yiping Zhang, Eui Jung Kim, Sung Hong Hahn, and Seung Gie Seong

Appl. Phys. Lett. 100, 101906 (2012); http://dx.doi.org/10.1063/1.3692584 (4 pages) | Cited 4 times

Online Publication Date: 8 March 2012

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Understanding the defect physics of ZnO is crucial in controlling its properties for various applications. We report the observation of an interesting 1.64 eV near-infrared (NIR) photoluminescence from ZnO and its evolution with annealing temperature. Based on a recent calculation on the transition levels of native point defects of ZnO [A. Janotti and C. G. Van de Walle, Phys. Rev. B 76, 165202 (2007)], the NIR emission can be successfully explained by the donor-acceptor transition between VO and VZn and/or the radiative recombination of shallowly trapped electrons with deeply trapped holes at Oi.
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78.55.Et II-VI semiconductors
71.55.Gs II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.J- Point defects and defect clusters

Photoluminescence associated with basal stacking faults in c-plane ZnO epitaxial film grown by atomic layer deposition

S. Yang, C. C. Kuo, W.-R. Liu, B. H. Lin, H.-C. Hsu, C.-H. Hsu, and W. F. Hsieh

Appl. Phys. Lett. 100, 101907 (2012); http://dx.doi.org/10.1063/1.3692730 (4 pages) | Cited 3 times

Online Publication Date: 8 March 2012

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Basal plane stacking faults (BSFs) with density of ∼1 × 106 cm−1 are identified as the dominant defect in the annealed ZnO thin films grown on c-plane sapphire by atomic layer deposition. The dominant peak centered at 3.321 eV in low-temperature photoluminescence measurements is attributed to the emission from the BSFs. The emission mechanism is considered to be the confined indirect excitons in the region of quantum-well-like structure formed by the BSFs. The observed energy shift of 19 meV with respect to the BSF-bounded exciton at low temperature may be caused by the localization effect associated with the coupling between BSF quantum wells.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Nn Stacking faults and other planar or extended defects
68.55.ag Semiconductors

Photoluminescence of Nd-doped SnO2 thin films

H. Rinnert, P. Miska, M. Vergnat, G. Schmerber, S. Colis, A. Dinia, D. Muller, G. Ferblantier, and A. Slaoui

Appl. Phys. Lett. 100, 101908 (2012); http://dx.doi.org/10.1063/1.3692747 (3 pages) | Cited 1 time

Online Publication Date: 8 March 2012

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Structural, optical, and electrical properties of Nd-doped SnOx thin films are reported. The atomic structure was characterized by x-ray diffraction and infrared absorption spectrometry. Investigation of the photoluminescence properties revealed Nd-related bands at 920 and 1100 nm for samples annealed at 700 °C, which present the tetragonal structure of the SnO2 rutile phase. Nd3+ ions can be indirectly excited and no concentration quenching was observed up to 3 at. %. It is concluded that Nd3+ ions are efficient optically active dopants in addition to be responsible of the observed electric conductivity improvement. These materials are then interesting for solar cell applications.
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78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
73.61.Le Other inorganic semiconductors
78.30.Hv Other nonmetallic inorganics
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology

Interlayer shear effect on multilayer graphene subjected to bending

YongKuan Shen and HengAn Wu

Appl. Phys. Lett. 100, 101909 (2012); http://dx.doi.org/10.1063/1.3693390 (3 pages) | Cited 3 times

Online Publication Date: 8 March 2012

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The effect of interlayer shear on bending property of multi-layer graphene is investigated using molecular dynamics simulations. Interlayer shear modulus is three orders lower than in-plane Young’s modulus, thus the bending behavior is dominated by interlayer shear. Continuum theory and atomistic simulations show that bending rigidity is proportional to layer number when the layer number exceeds 5. The small difference of these two proportional constants results from the stacking pattern, and turbostratic stacking decreases the interlayer shear modulus. For layer number smaller than 4, intrinsic ripples also play an important role and further decrease the interlayer shear modulus.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
81.05.ue Graphene
62.20.de Elastic moduli
62.20.F- Deformation and plasticity
68.35.Gy Mechanical properties; surface strains
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