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15 May 2006

Volume 88, Issue 20, Articles (20xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 203101 (2006); http://dx.doi.org/10.1063/1.2203932 (3 pages)

Andrea Ponzoni, Elisabetta Comini, Giorgio Sberveglieri, Jun Zhou, Shao Zhi Deng, Ning Sheng Xu, Yong Ding, and Zhong Lin Wang
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Ultrasensitive and highly selective gas sensors using three-dimensional tungsten oxide nanowire networks

Andrea Ponzoni, Elisabetta Comini, Giorgio Sberveglieri, Jun Zhou, Shao Zhi Deng, Ning Sheng Xu, Yong Ding, and Zhong Lin Wang

Appl. Phys. Lett. 88, 203101 (2006); http://dx.doi.org/10.1063/1.2203932 (3 pages) | Cited 132 times

Online Publication Date: 15 May 2006

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Three-dimensional (3D) tungsten oxide nanowire networks have been demonstrated as a high-surface area material for building ultrasensitive and highly selective gas sensors. Utilizing the 3D hierarchical structure of the networks, high sensitivity has been obtained towards NO2, revealing the capability of the material to detect concentration as low as 50 ppb (parts per billion). The distinctive selectivity at different working temperatures is observed for various gases. The results highlight that the nanobelts (nanowires) technology can be adopted for the development of gas sensors with performances suitable for practical applications.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis

Gold-nanoparticles-induced pattern metallization on high-roughness diamond film surfaces

Ruhai Tian and Jinfang Zhi

Appl. Phys. Lett. 88, 203102 (2006); http://dx.doi.org/10.1063/1.2203749 (3 pages) | Cited 1 time

Online Publication Date: 15 May 2006

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In this letter, we report an approach toward the pattern metallization of high roughness diamond film surfaces under mild experimental conditions. First, hydrogen-terminated diamond film surfaces were activated through bonding with allylamine molecules under 254 nm UV light irradiation. Then, amino prepatterns on the diamond surfaces were constructed by a photolithography process. Subsequently, gold nanoparticle (AuNP) patterns were obtained through the immobilization of 15±3 nm AuNPs on the amino prepatterns and the remnant photoresist was removed by rinsing with acetone. Finally, the AuNP patterns were enhanced through silver deposition and intact silver-gold micropatterns were constructed on diamond surfaces.
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81.16.Rf Micro- and nanoscale pattern formation
85.40.Ls Metallization, contacts, interconnects; device isolation
81.16.Nd Micro- and nanolithography
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
85.40.Hp Lithography, masks and pattern transfer
68.35.B- Structure of clean surfaces (and surface reconstruction)

Nanocrystalline dye-sensitized solar cell/copper indium gallium selenide thin-film tandem showing greater than 15% conversion efficiency

P. Liska, K. R. Thampi, M. Grätzel, D. Brémaud, D. Rudmann, H. M. Upadhyaya, and A. N. Tiwari

Appl. Phys. Lett. 88, 203103 (2006); http://dx.doi.org/10.1063/1.2203965 (3 pages) | Cited 47 times

Online Publication Date: 15 May 2006

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Multijunction stacked (tandem) solar cells can increase the overall photovoltaic conversion efficiency by optimal utilization of the solar spectrum in individual cells. We demonstrate that a photovoltaic tandem cell comprising a nanocrystalline dye-sensitized solar cell as a top cell for high-energy photons and a copper indium gallium selenide thin-film bottom cell for lower-energy photons produces AM 1.5 solar to electric conversion efficiencies greater than 15%.
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84.60.Jt Photoelectric conversion
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
61.46.Hk Nanocrystals
85.60.-q Optoelectronic devices

Step ordering induced by nonplanar patterning of GaAs surfaces

A. Dalla Volta, D. D. Vvedensky, N. Gogneau, E. Pelucchi, A. Rudra, B. Dwir, E. Kapon, and C. Ratsch

Appl. Phys. Lett. 88, 203104 (2006); http://dx.doi.org/10.1063/1.2204441 (3 pages) | Cited 4 times

Online Publication Date: 15 May 2006

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We report the observation and theory of the morphological evolution of vicinal (001) ridges on V-grooved GaAs surfaces during metal organic vapor-phase epitaxy. The pattern of the nonplanar substrate induces unusual ordering of monatomic steps, different from the free step flow observed on a nonpatterned vicinal surface. The step edges develop profiles that kinetic Monte Carlo simulations reveal are determined by the width of the ridges between neighboring V grooves and the kinetics of interfacet mass migration between the ridge and the bounding sidewalls of the V groove.
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68.47.Fg Semiconductor surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)

Effective fabrication of three-dimensional nano/microstructures in a single step using multilayered stamp

Sang-Hu Park, Tae-Woo Lim, Dong-Yol Yang, Jun-Ho Jeong, Ki-Don Kim, Kwang-Sup Lee, and Hong-Jin Kong

Appl. Phys. Lett. 88, 203105 (2006); http://dx.doi.org/10.1063/1.2204448 (3 pages) | Cited 15 times

Online Publication Date: 15 May 2006

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A technique in ultraviolet nanoimprint lithography (UV-NIL) for the creation of three-dimensional (3D) nanopatterns in a single step is proposed. The single-step fabrication of 3D or multilevel structures has a multitude of benefits. Inherent in this is the elimination of a need for alignment for multilevel fabrications as well as being a cost effective and simple process. For 3D UV-NIL, a trial in the fabrication of multilayered stamps has been conducted employing two-photon polymerization and diamondlike carbon (DLC) coating technique. The DLC coating layer enables the polymer patterns to be used effectively as a stamp without the need for an antiadhesion material. Additionally, O2-plasma ashing has the potential for an epoch-making improvement of the precision of polymer patterns with a linewidth of 60 nm. Overall, several fine patterns are imprinted using the multilayered stamp onto a UV-curable resist via a single-step process without any identifiable damage.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Nd Micro- and nanolithography
82.35.-x Polymers: properties; reactions; polymerization
81.65.-b Surface treatments

Self-assembly from the branch pattern to parallel wire array in electrodeposition

Mingzhe Zhang, Guihong Zuo, Zhaocun Zong, Haiyong Chen, Zhi He, Chunming Yang, Dongmei Li, and Guangtian Zou

Appl. Phys. Lett. 88, 203106 (2006); http://dx.doi.org/10.1063/1.2203956 (3 pages) | Cited 6 times

Online Publication Date: 16 May 2006

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We report a self-organized copper electrodeposition without imposed templates and induced additives. The deposit morphology on the silicon substrate varies from a branch to a parallel pattern by changing the applied voltage. We suggest that there are two essential factors for the formation of such kind of copper wire arrays. One is a proper electric potential distribution near the tip of the copper wire which dictates the direction of the solute transport. The other one is that the cathode overpotential and the equilibrium potential of reaction should remain unchanged at the growing interface.
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81.07.Bc Nanocrystalline materials
82.45.Yz Nanostructured materials in electrochemistry
81.16.Dn Self-assembly
81.15.Pq Electrodeposition, electroplating
82.45.Qr Electrodeposition and electrodissolution
61.46.-w Structure of nanoscale materials

Black nonreflecting silicon surfaces for solar cells

Svetoslav Koynov, Martin S. Brandt, and Martin Stutzmann

Appl. Phys. Lett. 88, 203107 (2006); http://dx.doi.org/10.1063/1.2204573 (3 pages) | Cited 88 times

Online Publication Date: 16 May 2006

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We present a wet chemical process for nanoscale texturing of Si surfaces, which results in an almost complete suppression of the reflectivity in a broad spectral range, leading to black Si surfaces. The process affects only the topmost 200–300 nm of the material and is independent of the surface orientation and doping. Thus, it can be applied to various structural forms of bulk silicon (single, poly-, or multicrystalline) as well as to thin Si films (amorphous or microcrystalline). The optical properties of various black Si samples are presented and discussed in correlation with the surface morphology.
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68.47.Fg Semiconductor surfaces
81.05.Cy Elemental semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
84.60.Jt Photoelectric conversion

Memory emission of printed carbon nanotube cathodes

Tao Feng, Lijuan Dai, Jun Jiang, Xi Wang, Xianghuai Liu, Shichang Zou, Qiong Li, and Jingfang Xu

Appl. Phys. Lett. 88, 203108 (2006); http://dx.doi.org/10.1063/1.2204576 (3 pages) | Cited 6 times

Online Publication Date: 16 May 2006

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The memory emission (ME) effect of printed carbon nanotube cathodes (PCNTCs) was reported. If the surface of PCNTCs is marked in a pattern by some methods, the emission image of this cathode will be the figure of the same pattern, just like the PCNTCsremember what happened in the past. We named this phenomenon as “memory emission.” According to the finding of field emission scanning electron microcopy, we suggested that the connecting CNT bundles protruding to the substrate and the electron conductive probability increasing from the substrate to the topside CNT emitter, which result in the emission enhancement of the marked place, were the reasons of the ME effect of PCNTCs. With the help of the ME effect of PCNTCs, the well-patterned emission image could easily be obtained.
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85.35.Kt Nanotube devices
85.45.Db Field emitters and arrays, cold electron emitters

Influence of alkyl chain substitution on sexithienyl-metal interface morphology and energetics

S. Duhm, H. Glowatzki, J. P. Rabe, N. Koch, and R. L. Johnson

Appl. Phys. Lett. 88, 203109 (2006); http://dx.doi.org/10.1063/1.2204834 (3 pages) | Cited 13 times

Online Publication Date: 16 May 2006

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The interface between Ag(111) and vacuum sublimated α,ω-dihexylsexithienyl (DH6T) was investigated using ultraviolet photoelectron spectroscopy and atomic force microscopy. While the monolayer of DH6T is lying flat on the metal surface, we found that already in the second molecular layer the molecules are almost standing upright. This abrupt change in molecular orientation lowered the hole injection barrier (Δh) of DH6T/Ag by 0.5 eV between monolayer and multilayer. Δh for DH6T multilayers was even lowered by 0.8 eV compared to unsubstituted sexithienyl multilayers. The reduction of Δh is attributed to the electronic decoupling of molecules in the first from those in the second layer via the hexyl chains.
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68.35.Ct Interface structure and roughness
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
68.37.Ps Atomic force microscopy (AFM)
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
79.60.Jv Interfaces; heterostructures; nanostructures
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Nonlinear optical response of a single self-assembled InGaAs quantum dot: A femtojoule pump-probe experiment

M. Wesseli, C. Ruppert, S. Trumm, H. J. Krenner, J. J. Finley, and M. Betz

Appl. Phys. Lett. 88, 203110 (2006); http://dx.doi.org/10.1063/1.2205722 (3 pages) | Cited 6 times

Online Publication Date: 16 May 2006

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A single InGaAs/GaAs quantum dot is addressed in a two-color femtosecond transmission experiment in the optical near-field of a nanometer-scale shadow mask. After resonant excitation of the wetting layer beneath the nanoisland, we detect transmission changes of the quantum dot with narrow band femtojoule probe pulses. We find bleaching signals in the order of 10−5 that arise from individual interband transitions. Moreover, the nonlinear optical response reveals a picosecond dynamics associated with carrier relaxation in the quantum dot. As a result, we have developed an ultrafast optical tool for both manipulation and readout of a single self-assembled quantum dot.
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78.67.Hc Quantum dots
78.47.-p Spectroscopy of solid state dynamics

Soft landing of silicon nanocrystals in plasma enhanced chemical vapor deposition

Nihed Chaâbane, Veinardi Suendo, Holger Vach, and Pere Roca i Cabarrocas

Appl. Phys. Lett. 88, 203111 (2006); http://dx.doi.org/10.1063/1.2204439 (3 pages) | Cited 15 times

Online Publication Date: 17 May 2006

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Plasma-generated silicon nanocrystals have been selectively trapped on a cooled substrate to yield nanocrystalline films. We here present experimental evidence that the contribution of positively charged nanocrystals largely dominates the film deposition. As a direct application, we illustrate how the use of a simple substrate bias voltage allows us to “toggle switch” between 100% nanocrystalline and 100% amorphous layers. Moreover, we demonstrate that the applied bias voltage can be used to “tune” the photoluminescence of the nanocrystals between 630 and 730 nm.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Db Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
52.77.Dq Plasma-based ion implantation and deposition

Novel deformation mechanism of twinned nanowires

Jian Wang and Hanchen Huang

Appl. Phys. Lett. 88, 203112 (2006); http://dx.doi.org/10.1063/1.2204760 (3 pages) | Cited 40 times

Online Publication Date: 17 May 2006

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This letter reports a novel deformation mechanism of twinned Cu nanowires, based on molecular statics and dynamics simulations. Under mechanical loading, Shockley partial dislocations nucleate and glide on a {111} plane toward a twin boundary. Upon penetration of the twin boundary, a dislocation with Burgers vector of ½〈110〉 nucleates and glides on a {100} plane, instead of conventional {111} planes. The dislocation nucleation on {100} planes is facilitated by the intersection of surface and twin boundary, and the dislocation glide is primarily facilitated by the matching of Burgers vector along the normal direction of the twin boundary.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Mm Grain and twin boundaries
61.46.Hk Nanocrystals

Effect of uniaxial stress on excitons in a self-assembled quantum dot

Stefan Seidl, Martin Kroner, Alexander Högele, Khaled Karrai, Richard J. Warburton, Antonio Badolato, and Pierre M. Petroff

Appl. Phys. Lett. 88, 203113 (2006); http://dx.doi.org/10.1063/1.2204843 (3 pages) | Cited 64 times

Online Publication Date: 17 May 2006

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The fine structure of the neutral exciton in a single self-assembled InGaAs quantum dot is investigated under the effect of an applied uniaxial stress. The spectrum of the excitonic Rayleigh scattering was measured in reflectivity using high-resolution laser spectroscopy while the sample was submitted to a tunable uniaxial stress along its [110] crystal axis. We show that using this stretching technique, the quantum dot potential is elastically deformable such that the exciton fine structure splitting can be substantially reduced.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
73.21.La Quantum dots
71.35.-y Excitons and related phenomena
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity

Mechanism of emission-energy tuning in InAs quantum dots using a thin upper confinement layer

Z. Z. Sun, S. F. Yoon, W. K. Loke, and C. Y. Liu

Appl. Phys. Lett. 88, 203114 (2006); http://dx.doi.org/10.1063/1.2206248 (3 pages) | Cited 2 times

Online Publication Date: 18 May 2006

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The emission-energy tuning mechanism in InAs quantum dots using a thin upper confinement layer (UCL) was investigated. By comparing the emission-energy tuning ability of InGaP and InGaAs UCLs in InAs/UCL dot structures, strain adjustment rather than mass transport was identified as the dominant mechanism responsible for emission-energy tuning in the InAs quantum dots. An explanation of the general emission-energy tuning behavior by the UCL was given based on strain adjustment mechanism.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)

Molecular dynamic simulations and atomic structures of amorphous materials

G. L. Chen, X. J. Liu, X. D. Hui, H. Y. Hou, K. F. Yao, C. T. Liu, and J. Wadsworth

Appl. Phys. Lett. 88, 203115 (2006); http://dx.doi.org/10.1063/1.2198015 (3 pages) | Cited 9 times

Online Publication Date: 18 May 2006

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A long-standing issue of using molecular dynamics (MD) to simulate local atomic structures in nonequilibrium metals and alloys is the huge difference in cooling rates used in experimental studies and theoretical calculations. In this study, a unique approach was introduced to correct the fast time steps involved in the MD calculations. This approach has demonstrated various medium-range ordered zones with imperfect ordered packing, which are verified experimentally by high-resolution transmission electron microscopy and its selected simulation imaging of Zr2Ni glass.
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61.43.Bn Structural modeling: serial-addition models, computer simulation
61.43.Fs Glasses
68.37.Lp Transmission electron microscopy (TEM)

Hooge’s constant for carbon nanotube field effect transistors

Masa Ishigami, J. H. Chen, E. D. Williams, David Tobias, Y. F. Chen, and M. S. Fuhrer

Appl. Phys. Lett. 88, 203116 (2006); http://dx.doi.org/10.1063/1.2206685 (3 pages) | Cited 33 times

Online Publication Date: 18 May 2006

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The 1/f noise in individual semiconducting carbon nanotubes (s-CNT) in a field effect transistor configuration has been measured in ultrahigh vacuum and following exposure to air. The amplitude of the normalized current spectral noise density is independent of source-drain current and inversely proportional to gate voltage, to channel length, and therefore to carrier number, indicating that the noise is due to mobility rather than number fluctuations. Hooge’s constant for s-CNT is found to be (9.3±0.4)×10−3 The magnitude of the 1/f noise is substantially decreased by exposing the devices to air.
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85.30.Tv Field effect devices
72.70.+m Noise processes and phenomena
85.35.Kt Nanotube devices

Branched Ta nanocolumns grown by glancing angle deposition

C. M. Zhou and D. Gall

Appl. Phys. Lett. 88, 203117 (2006); http://dx.doi.org/10.1063/1.2204759 (3 pages) | Cited 35 times

Online Publication Date: 18 May 2006

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Periodic arrays of Ta nanocolumns, 200 nm wide and 600 nm tall, were grown by glancing angle sputter deposition onto self-assembled close-packed arrays of 260-nm-diameter silica spheres. Each sphere leads to the development of a single Ta column. As growth progresses, roughening of the column top surfaces causes branching of some columns into subcolumns. The measured fraction of branched columns fb decreases with increasing growth temperature, from 30% at 200 °C to 4% at 700 °C. This is attributed to the increased adatom mobility at elevated temperatures, leading to a larger average separation of growth mounds and, in turn, lower nucleation probabilities for subcolumns. Branching into 3 and 4 subcolumns exhibits probabilities proportional to fb2 and fb3, respectively. A fit of the data with a simple nucleation model provides an effective activation energy for Ta surface diffusion of 2.0 eV.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.46.-w Structure of nanoscale materials
81.15.Cd Deposition by sputtering
81.16.Dn Self-assembly
68.43.Mn Adsorption kinetics
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation

Quasi-one-dimensional quantum well on Si(100) surface crafted by using scanning tunneling microscopy tip

Keisuke Sagisaka and Daisuke Fujita

Appl. Phys. Lett. 88, 203118 (2006); http://dx.doi.org/10.1063/1.2204762 (3 pages) | Cited 9 times

Online Publication Date: 18 May 2006

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We fabricated quasi-one-dimensional (1D) quantum wells on the Si(100) surface by using a scanning tunneling microscopy (STM) tip. Electron waves were confined to a single silicon dimer row by two tungsten nanodots that were separated by several nanometers. The tungsten dots were deposited by point contact between the STM tip and the sample. The size of the dots we created on the Si(100) surface was as small as the width of a single dimer. Differential conductance mapping and scanning tunneling spectroscopy detected different quantum states confined to the quasi-1D quantum well as changing bias voltage.
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81.07.St Quantum wells
81.16.Ta Atom manipulation
73.21.Fg Quantum wells
73.63.Hs Quantum wells
68.65.Fg Quantum wells
73.23.-b Electronic transport in mesoscopic systems

High photocurrent conversion efficiency in self-organized porous WO3

S. Berger, H. Tsuchiya, A. Ghicov, and P. Schmuki

Appl. Phys. Lett. 88, 203119 (2006); http://dx.doi.org/10.1063/1.2206696 (3 pages) | Cited 51 times

Online Publication Date: 18 May 2006

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Self-organized porous structures of WO3 were grown on tungsten by an anodic oxidation, and their photoelectrochemical properties were characterized. The porous WO3 layers show a regular morphology with average pore sizes of approximately 70 nm and a pore wall thickness of approximately 10 nm. As formed layers show an amorphous structure but the layers can be altered to a crystalline monoclinic structure by thermal annealing. The annealed porous WO3 layers show a very high specific photocurrent conversion efficiency.
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81.05.Rm Porous materials; granular materials
72.40.+w Photoconduction and photovoltaic effects
61.43.Gt Powders, porous materials
82.45.-h Electrochemistry and electrophoresis
82.50.-m Photochemistry
81.40.Gh Other heat and thermomechanical treatments

Subgap structure in resistively shunted superconducting atomic point contacts

Zhenting Dai and Alexei Marchenkov

Appl. Phys. Lett. 88, 203120 (2006); http://dx.doi.org/10.1063/1.2206697 (3 pages)

Online Publication Date: 18 May 2006

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We report the transport properties of superconducting atomic-size contacts in different resistive environments. Embedding resistive shunts close to a junction affects the spectrum of multiple Andreev reflections. In particular, the subgap structure in current-voltage characteristics shifts to lower voltages. Experiments were performed in a special-purpose circuit that enables both voltage-biased and phase-biased measurements on the same contact configuration. Methods developed for full characterization of superconducting point contacts can be directly applied in this layout.
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74.50.+r Tunneling phenomena; Josephson effects
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.81.Fa Josephson junction arrays and wire networks
85.25.Cp Josephson devices
74.25.F- Transport properties
74.25.Jb Electronic structure (photoemission, etc.)

In-line aligned and bottom-up Ag nanorods for surface-enhanced Raman spectroscopy

Motofumi Suzuki, Wataru Maekita, Yoshinori Wada, Kaoru Nakajima, Kenji Kimura, Takao Fukuoka, and Yasushige Mori

Appl. Phys. Lett. 88, 203121 (2006); http://dx.doi.org/10.1063/1.2205149 (3 pages) | Cited 8 times

Online Publication Date: 18 May 2006

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We have demonstrated surface-enhanced Raman spectroscopy on arrays of Ag nanorods aligned in line by a dynamic oblique deposition technique. For the light polarized along the major axis of the nanorods, the plasma resonance of the Ag nanorods has been tuned to a wavelength suitable for Raman spectroscopy. The average width and the length-to-width ratio of the resulting nanorods are 56 nm and 3.5, respectively, and the nanorods align in line with small gaps of a few 10 nm. The Raman scattering for the polarized light along the nanorods is enhanced significantly as compared with that perpendicular to the nanorods. This polarization dependent Raman enhancement is attributed to the local field concentration at the ends of the nanorods. Since the preparation process is physical and completely bottom up, it is robust in its selection of the materials and is useful in providing the surface-enhanced Raman scattering sensors at low cost.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
78.30.Er Solid metals and alloys

Visible light diffraction studies on periodically aligned arrays of carbon nanotubes: Experimental and theoretical comparison

J. Rybczynski, K. Kempa, Y. Wang, Z. F. Ren, J. B. Carlson, B. R. Kimball, and G. Benham

Appl. Phys. Lett. 88, 203122 (2006); http://dx.doi.org/10.1063/1.2205165 (3 pages) | Cited 13 times

Online Publication Date: 18 May 2006

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We have investigated visible light diffraction on honeycomb arrays of aligned carbon nanotubes grown on nickel nanoparticles prepared using the nanosphere lithography. A monolayer of 980 nm polystyrene spheres was used as the mask for the deposition of nickel nanoparticles from which carbon nanotubes of 100 nm in diameter and up to a couple of microns in length were grown. We show that a standard theory of diffraction from point scatterers explains all the observed diffraction features including Bragg’s law and the strong enhancement of the second and fifth order diffraction spots.
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78.67.Ch Nanotubes
81.07.De Nanotubes
81.07.Bc Nanocrystalline materials
81.07.Wx Nanopowders
61.46.Fg Nanotubes
81.16.Nd Micro- and nanolithography

Synthesis and laser annealing of embedded CdSe-nanoparticles in SiO2 by pulsed excimer laser radiation

P. Huber, H. Karl, and B. Stritzker

Appl. Phys. Lett. 88, 203123 (2006); http://dx.doi.org/10.1063/1.2205721 (3 pages) | Cited 4 times

Online Publication Date: 18 May 2006

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CdSe-semiconductor nanocrystals embedded in SiO2 on silicon have been synthesized by ion implantation of Cd+ and Se+ followed by pulsed excimer laser annealing at room temperature. Transmission electron microscopy and x-ray diffraction-analysis results suggest that wurzite-type embedded CdSe nanocrystals have been formed. Since laser annealing can be applied locally this opens a route towards spatially selective annealing. In a second type of experiment pulsed laser annealing was performed on embedded CdSe nanoparticles synthesized by standard thermal annealing resulting in oriented ellipsoidal deformation and morphological changes of the larger precipitates. Computer simulation results suggest a size-selective temperature increase of the CdSe nanocrystals as the underlying mechanism.
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61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.up Other materials
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Smart photochromic gratings with switchable wettability realized by green-light interferometry

Elisa Mele, Dario Pisignano, Maria Varda, Maria Farsari, George Filippidis, Costas Fotakis, Athanassia Athanassiou, and Roberto Cingolani

Appl. Phys. Lett. 88, 203124 (2006); http://dx.doi.org/10.1063/1.2198509 (3 pages) | Cited 11 times

Online Publication Date: 19 May 2006

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We demonstrate the enhancement of the wetting properties of smart photochromic surfaces by a specifically developed, gentle interferometric patterning employing green light. We realized photochromic gratings with 2.5–10.0 μm period by a blend consisting of a green-curable matrix and spiropyran molecules. The structured surfaces exhibit photocontrolled and reversible wettability, and enhanced hydrophilicity with respect to the native substrates. The dynamics of liquid spreading onto the gratings was also investigated, and the wetting behavior analyzed according to Wenzel’s [ Ind. Eng. Chem. 28, 988 (1936) ] model for rough surfaces. These results indicate switchable gratings as promising functional components for microfluidics and modulation, and green-light interferometry as a reliable lithographic method for patterning organics without degradation or photochemical reactions.
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42.79.Dj Gratings
07.60.Ly Interferometers
68.08.Bc Wetting
68.03.Cd Surface tension and related phenomena

Preparation of a superhydrophobic surface by mixed inorganic-organic coating

Michele Ferrari, Francesca Ravera, and Libero Liggieri

Appl. Phys. Lett. 88, 203125 (2006); http://dx.doi.org/10.1063/1.2205725 (3 pages) | Cited 11 times

Online Publication Date: 19 May 2006

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In recent years, superhydrophobic surfaces, with a water-contact angle greater than 150°, have attracted great interest for both fundamental research and practical applications. Due to the small area these surfaces show when in contact with water, interactions with aqueous environment are usually strongly reduced. An original methodology based on a mixed inorganic-organic coating in a multistep procedure is described here allowing a superhydrophobic surface to be prepared starting with a mechanical treatment of a glass surface.
Show PACS
81.07.Pr Organic-inorganic hybrid nanostructures
68.03.Cd Surface tension and related phenomena
81.65.-b Surface treatments
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