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8 May 2006

Volume 88, Issue 19, Articles (19xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 193113 (2006); http://dx.doi.org/10.1063/1.2202003 (3 pages)

Fa-Quan He and Ya-Pu Zhao
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Transmission electron microscopy investigation of self-assembly ZnO twinning nanostructures

Z. H. Zhang, H. H. Liu, J. K. Jian, K. Zou, and X. F. Duan

Appl. Phys. Lett. 88, 193101 (2006); http://dx.doi.org/10.1063/1.2198011 (3 pages) | Cited 10 times

Online Publication Date: 8 May 2006

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Self-assembly ZnO twinning nanostructures are studied by transmission electron microscopy systematically. Selected area electron diffraction and high-resolution transmission electron microscopy observations indicate two types of twin boundaries (01mathmath) and (01math3) appeared in the same nanostructure and the twinning relationships are well defined. Convergent-beam electron diffraction techniques determine the polarities of the building blocks are all Zn terminated with the help of theoretical simulations, which is further confirmed by electron energy loss spectroscopy under (0002) and (000math) Bragg conditions.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Mm Grain and twin boundaries
81.16.Dn Self-assembly
79.20.Uv Electron energy loss spectroscopy

Coalescence inhibition of hydrous RuO2 crystallites prepared by a hydrothermal method

Kuo-Hsin Chang and Chi-Chang Hu

Appl. Phys. Lett. 88, 193102 (2006); http://dx.doi.org/10.1063/1.2200154 (3 pages) | Cited 25 times

Online Publication Date: 8 May 2006

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Coalescence of particulates accompanied with crystal growth upon annealing at/above 200 °C, found for hydrous RuO2 (RuO2∙nH2O) prepared by a sol-gel process, is effectively inhibited by the formation of RuO2∙nH2O nanocrystallites in a hydrothermal process. This thermal stability, attributable to the barrier originated from the lattice energy of crystallites, maintains high water content, nanocrystalline structure, and porous nature of RuO2∙nH2O annealed at elevated temperatures from 200 to 400 °C. A hydrothermal derived RuO2-based supercapacitor with high specific capacitance (ca. 200 F g−1 measured at 100 mA cm−2) and a cycle lifetime longer than 40 000 cycles, resulting from thermal stability, is demonstrated.
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81.07.Bc Nanocrystalline materials
81.10.Dn Growth from solutions
61.46.Hk Nanocrystals
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.40.Gh Other heat and thermomechanical treatments
82.47.Uv Electrochemical capacitors; supercapacitors

Directed organization of gold nanoclusters on silver nanowires: A step forward in heterostructure assembly

Jadab Sharma, J. P. Vivek, Kunjukrishna P. Vijayamohanan, Poonam Singh, and C. V. Dharmadhikari

Appl. Phys. Lett. 88, 193103 (2006); http://dx.doi.org/10.1063/1.2200284 (3 pages) | Cited 3 times

Online Publication Date: 8 May 2006

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We investigate the directed assembly of tridecylamine protected gold nanoclusters of 4–5 nm size on functionalized silver nanowires of 55–60 nm diameter and the electron transfer behavior of this integrated structure using transmission electron microscopy, non-contact atomic force microscopy, and scanning tunneling microscopy/spectroscopy. Linear I-V for bare silver nanowire suggests metallic behavior but high tunnel resistance indicates presence of insulating layer on the surface. Identical I-Vs obtained for isolated gold nanoparticle and heterostructure suggests that electron transport across nanowires in the latter is governed by gold nanoparticles in contrast to expected ballistic or diffusive transport along their length.
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81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
81.16.-c Methods of micro- and nanofabrication and processing
73.63.Bd Nanocrystalline materials
61.46.Bc Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)

Role of cylindrical surface plasmons in enhanced transmission

Michael I. Haftel, Carl Schlockermann, and Girsh Blumberg

Appl. Phys. Lett. 88, 193104 (2006); http://dx.doi.org/10.1063/1.2201884 (3 pages) | Cited 22 times

Online Publication Date: 8 May 2006

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Utilizing normal mode analysis of Maxwell’s equations and finite-difference-time-domain simulations we find extraordinary optical transmission in nanoarrays of insulating coaxial cylindrical rings embedded in metal films. As the rings become narrower we find transmission peaks at longer wavelengths, with the peak wavelength increasing indefinitely as the rings narrow. This behavior results from the excitation of cylindrical surface plasmon resonant modes on the cylindrical insulator-metal interfaces of the rings. These findings indicate that the excitation of cylindrical surface plasmons in these structures can produce propagating modes and enhanced transmission at wavelengths longer than those predicted previously.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.30.-j Infrared and Raman spectra
78.40.-q Absorption and reflection spectra: visible and ultraviolet

Shape-controlled growth of single-crystalline Ge nanostructures

Chang-Beom Jin, Jee-Eun Yang, and Moon-Ho Jo

Appl. Phys. Lett. 88, 193105 (2006); http://dx.doi.org/10.1063/1.2201899 (3 pages) | Cited 37 times

Online Publication Date: 8 May 2006

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We report the shape-controlled growth of single-crystalline germanium nanostructures by Au catalyst-assisted chemical-vapor syntheses using GeH4 as a precursor. By independently controlling the axial- and the radial-growth kinetics near the eutectic temperature of Au and Ge, we reproducibly direct the shape of Ge nanostructures from nanowires to nanocones with various aspect ratios. Based on our observation of the shape variation we discuss a phenomenological model of the growth of Ge nanostructures that goes beyond the conventional vapor-liquid-solid growth mechanism. The precise control of the shape in semiconductor nanostructures in our study suggests the implication of various applications into electronic and optical devices.
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81.05.Cy Elemental semiconductors
81.16.Hc Catalytic methods
68.65.La Quantum wires (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.Hk Nanocrystals

Registration of single quantum dots using cryogenic laser photolithography

Kwan H. Lee, Alex M. Green, Robert A. Taylor, David N. Sharp, Jan Scrimgeour, Olivia M. Roche, Jong H. Na, Anas F. Jarjour, Andrew J. Turberfield, Frederic S. F. Brossard, David A. Williams, and G. Andrew D. Briggs

Appl. Phys. Lett. 88, 193106 (2006); http://dx.doi.org/10.1063/1.2202193 (3 pages) | Cited 7 times

Online Publication Date: 9 May 2006

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We have registered the position of single InGaAs quantum dots using a cryogenic laser photolithography technique. This is an important advance towards the reproducible fabrication of solid-state cavity quantum electrodynamic devices, a key requirement for commercial exploitation of quantum information processing. The quantum dot positions were registered with an estimated accuracy of 50 nm by fabricating metal alignment markers around them. Photoluminescence spectra from quantum dots before and after marker fabrication were identical except for a small redshift ( ∼ 1 nm), probably introduced during the reactive ion etching.
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81.16.Nd Micro- and nanolithography
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.07.Ta Quantum dots
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
42.62.-b Laser applications

Deep levels in the band gap of the carbon nanotube with vacancy-related defects

Gunn Kim, Byoung Wook Jeong, and Jisoon Ihm

Appl. Phys. Lett. 88, 193107 (2006); http://dx.doi.org/10.1063/1.2202112 (3 pages) | Cited 19 times

Online Publication Date: 9 May 2006

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We study the modification in the electronic structure of the carbon nanotube induced by vacancy-related defects using the first-principles calculation. Three defect configurations which are likely to occur in semiconducting carbon nanotubes are considered. A vacancy-adatom complex is found to bring about a pair of localized states deep inside the energy gap. A pentagon-octagon-pentagon topological defect produced by the divacancy is structurally stable and gives rise to an unoccupied localized state in the gap. We also discuss the character of partially occupied localized state produced by a substitutional impurity plus a monovacancy.
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71.55.Cn Elemental semiconductors
71.20.Tx Fullerenes and related materials; intercalation compounds
71.15.-m Methods of electronic structure calculations
61.72.J- Point defects and defect clusters

Parametric resonance based scanning probe microscopy

M. Moreno-Moreno, A. Raman, J. Gomez-Herrero, and R. Reifenberger

Appl. Phys. Lett. 88, 193108 (2006); http://dx.doi.org/10.1063/1.2202132 (3 pages) | Cited 9 times

Online Publication Date: 9 May 2006

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We propose a mode of dynamic scanning probe microscopy based on parametric resonance for highly sensitive nanoscale imaging and force spectroscopy. In this mode the microcantilever probe is excited by means of a closed-loop electronic circuit that modulates the microcantilever stiffness at a frequency close to twice its natural resonance frequency. Under ambient conditions this parametric pumping leads to self-sustained oscillations in a narrow frequency bandwidth thereby resulting in exquisitely sharp, controllable, and non-Lorentzian resonance peaks. We discuss and demonstrate the potential of imaging and force spectroscopy using this mode.
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07.79.-v Scanning probe microscopes and components
68.37.-d Microscopy of surfaces, interfaces, and thin films
46.25.-y Static elasticity

Quantitative dynamic-mode scanning force microscopy in liquid

B. W. Hoogenboom, H. J. Hug, Y. Pellmont, S. Martin, P. L. T. M. Frederix, D. Fotiadis, and A. Engel

Appl. Phys. Lett. 88, 193109 (2006); http://dx.doi.org/10.1063/1.2202638 (3 pages) | Cited 35 times

Online Publication Date: 9 May 2006

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We describe a method to perform dynamic-mode scanning force microscopy in liquid with true atomic resolution. A frequency-modulation technique is used to maintain constant amplitude, phase, and frequency shift of the cantilever oscillation. As a consequence, the tip-sample interaction force is well defined and quantitative. The force sensitivity is demonstrated by imaging and deliberate bending of a peptide loop connecting transmembrane helices of the membrane protein bacteriorhodopsin. The experimental setup allows further enhancement of the force sensitivity by the use of small cantilevers.
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61.25.Em Molecular liquids
68.37.Ps Atomic force microscopy (AFM)
36.20.Hb Configuration (bonds, dimensions)
87.15.B- Structure of biomolecules
87.14.E- Proteins
87.64.Dz Scanning tunneling and atomic force microscopy

Full spectrum enhancement of the light harvesting efficiency of dye sensitized solar cells by including colloidal photonic crystal multilayers

A. Mihi, F. J. López-Alcaraz, and H. Míguez

Appl. Phys. Lett. 88, 193110 (2006); http://dx.doi.org/10.1063/1.2200746 (3 pages) | Cited 28 times

Online Publication Date: 9 May 2006

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Herein we report a theoretical analysis of the efficiency of dye sensitized solar cells in which colloidal crystals are introduced in different configurations. We find that piling up different lattice constant crystals leads to light harvesting enhancement in the whole dye absorption range. We provide the optimum structural features of such photonic crystal multilayer needed to achieve a photocurrent efficiency enhancement of around 60% with respect to standard dye sensitized solar cells. We demonstrate that this improvement is the result of the optical absorption amplification effect of slow photon resonant modes partially confined within the absorbing part of the cell by the mirror behavior of the colloidal superlattice.
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84.60.Jt Photoelectric conversion
42.70.Qs Photonic bandgap materials
82.70.Dd Colloids
72.40.+w Photoconduction and photovoltaic effects

Self-assembled Fe nanodots on Ge(001)

K. Jordan and I. V. Shvets

Appl. Phys. Lett. 88, 193111 (2006); http://dx.doi.org/10.1063/1.2201861 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2006

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The initial nucleation of Fe onto the (2×1) reconstructed Ge(001) surface is studied. Uniformly sized two-dimensional Fe dots are shown to nucleate. They have an apparent corrugation height ∼ 1.1 Å and lateral dimensions ∼ 12×8 Å2. Further to their uniform size, due to their registry with respect to the substrate, they are shown to nucleate on a single equivalent surface site. It is suggested that their stability is due to either a “magic” number effect or adsorbate-substrate interactions. Tunneling I(V) spectra show the dot/Ge(001) contact to exhibit marked current rectifying behavior, which is extremely well confined to the contact area.
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81.07.Bc Nanocrystalline materials
81.16.Dn Self-assembly
61.46.-w Structure of nanoscale materials
73.40.Ei Rectification

Selective wavelength tuning of self-assembled InAs quantum dots grown on InP

S. Barik, H. H. Tan, C. Jagadish, N. Vukmirović, and P. Harrison

Appl. Phys. Lett. 88, 193112 (2006); http://dx.doi.org/10.1063/1.2203333 (3 pages) | Cited 7 times

Online Publication Date: 9 May 2006

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We report the experimental results of tuning the emission wavelength of InAs/InP quantum dots (QDs) by varying either the GaAs interlayer thickness or the indium composition of the InxGa1−xAs interlayer. The InAs QDs are grown on lattice-matched GaInAsP or InP buffers and are capped with an InP layer. As/P exchange is prominent when the QDs are grown on an InP buffer. A model is developed which considers the As/P exchange, gallium interdiffusion, strain, and barrier height. Our theoretical and experimental results show that gallium interdiffusion and the As/P exchange reaction are mainly responsible for the observed shifts in the QD emission wavelength. The model shows that gallium interdiffusion from the interlayer to the InAs QDs grown on a GaInAsP buffer can be utilized to selectively tune the InAs QD emission wavelength over a wide range.
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78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
68.35.Fx Diffusion; interface formation
68.60.Bs Mechanical and acoustical properties

Growth of ZnO nanotetrapods with hexagonal crown

Fa-Quan He and Ya-Pu Zhao

Appl. Phys. Lett. 88, 193113 (2006); http://dx.doi.org/10.1063/1.2202003 (3 pages) | Cited 30 times

Online Publication Date: 10 May 2006

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ZnO nanotetrapods with hexagonal crown were synthesized on a silicon wafer by vapor transport process at a low temperature of 630 °C and normal pressure without the presence of catalysts. The results demonstrated that the as-synthesized products with slender legs and regular hexagonal crown are single crystal with wurtzite structure and preferentially grow up along (001) direction. Photoluminescence spectra revealed that the green emission originated from oxygen vacancies overwhelmed that of the near-band-edge ultraviolet peak, which suggests the peculiar-shaped nanotetrapods may have potential applications in multichannel nano-optoelectronic devices.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Dz II-VI semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
78.55.Et II-VI semiconductors
61.46.-w Structure of nanoscale materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Self-assembled endotaxial α-FeSi2 nanowires with length tunability mediated by a thin nitride layer on (001)Si

S. Y. Chen, H. C. Chen, and L. J. Chen

Appl. Phys. Lett. 88, 193114 (2006); http://dx.doi.org/10.1063/1.2202701 (3 pages) | Cited 7 times

Online Publication Date: 10 May 2006

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Endotaxial growth of self-assembled α-FeSi2 nanowires (NWs) on (100)Si has been achieved by combining reactive deposition epitaxy and nitride-mediated epitaxy. The length and the length/width aspect ratio of metallic α-FeSi2 NWs could be increased more than 12 and 6 folds to 2 μm, and 200 respectively, with a narrow width of 5–10 nm after prolonged annealing. The adjustment capability is attributed to the diminished flux of Fe adatoms mediated by the Si3N4 barrier layer to allow more complete shape transition. The scheme represents a degree of control on the morphology of self-assembled epitaxial silicide NWs not achievable otherwise.
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81.16.Dn Self-assembly
68.65.La Quantum wires (patterned in quantum wells)
61.46.-w Structure of nanoscale materials
81.40.Gh Other heat and thermomechanical treatments

Synthesis and characterization of one-dimensional CdSe nanostructures

G. X. Wang, M. S. Park, H. K. Liu, D. Wexler, and J. Chen

Appl. Phys. Lett. 88, 193115 (2006); http://dx.doi.org/10.1063/1.2202725 (3 pages) | Cited 11 times

Online Publication Date: 10 May 2006

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One-dimensional (1D) CdSe nanostructures, including nanowires, nanotubes, nanorods, nanobelts, and even nanostructures resembling saws and tree branches, have been synthesized by sublimation of CdSe powders under various experimental conditions. These 1D CdSe nanostructures were characterized by scanning electron microscopy, high resolution transmission electron microscopy observations, and Raman spectroscopy. Energy dispersive x-ray spectroscopy analysis confirmed the chemical stoichiometry of the CdSe nanostructures. It was found that the geometrical morphologies of the CdSe 1D nanostructures were significantly influenced by the synthetic parameters. Raman spectra of CdSe nanowires show an upward shift of the 2LO phonon peak.
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81.07.Bc Nanocrystalline materials
81.07.De Nanotubes
81.05.Dz II-VI semiconductors
61.46.Fg Nanotubes
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.30.Fs III-V and II-VI semiconductors

Field-emission-induced growth of nanowire between electrodes

K. S. Yeong, J. B. K. Law, and J. T. L. Thong

Appl. Phys. Lett. 88, 193116 (2006); http://dx.doi.org/10.1063/1.2202733 (3 pages) | Cited 5 times

Online Publication Date: 10 May 2006

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We demonstrate the growth of a tungsten nanowire between two microtip electrodes by the field-emission-induced growth process. A nanowire is grown from the cathode towards the opposing biased anode in a quasicontinuous manner. In order to study the nanowire growth process, the wire is grown in a stepwise manner until it bridges the cathode and the anode. The growth of the nanowire across the cathode-anode gap falls into four different regimes of initiation, steady growth, close-gap growth, and finally bridging of electrodes. The profile of the field-enhancement factor of the nanowire field emitter during growth matches the results from electrostatic modeling.
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81.07.Bc Nanocrystalline materials
79.70.+q Field emission, ionization, evaporation, and desorption
68.65.La Quantum wires (patterned in quantum wells)

Energetic and magnetic properties of transition-metal nanowire encapsulated BxCyNz composite nanotubes

G. W. Peng, A. C. H. Huan, and Y. P. Feng

Appl. Phys. Lett. 88, 193117 (2006); http://dx.doi.org/10.1063/1.2202737 (3 pages) | Cited 13 times

Online Publication Date: 10 May 2006

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We present a comparative study on the structural, energetic, and magnetic properties of carbon and BxCyNz composite single-walled nanotubes filled with transition-metal (TM) nanowires using first-principles calculations. It was found that interaction between the nanotube and nanowire weakens the magnetism of the nanowire. TM/BC3 was found exceptionally stable and its formation is exothermic. The resulting hybrid structure, however, has the weakest magnetism compared to other systems for the same tube size. Similar to hybrid structures based on carbon and BN nanotubes, both TM/BC2N and TM/BC3 hybrid structures show high spin polarization which may have potential applications in spintronics.
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61.46.Fg Nanotubes
75.50.Dd Nonmetallic ferromagnetic materials
71.15.-m Methods of electronic structure calculations
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
73.22.-f Electronic structure of nanoscale materials and related systems

Role of elastic anisotropy in the vertical alignment of In(Ga)As quantum dot superlattices

M. Gutiérrez, M. Herrera, D. González, R. García, and M. Hopkinson

Appl. Phys. Lett. 88, 193118 (2006); http://dx.doi.org/10.1063/1.2202190 (3 pages) | Cited 10 times

Online Publication Date: 11 May 2006

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This letter shows the effect of the elastic anisotropic strain field in the vertical stacking for multilayer In(Ga)As/GaAs quantum dot (QD) structures grown by molecular beam epitaxy. This effect explains the QD enlargement in vertical correlated stacking and the possibility to obtain QD vertical anticorrelated stacking. The anticorrelation configuration in these structures is dependent not only on the QD size and on the interlayer spacing but also on the QD density. With appropriate choice of these structural parameters, a QD body centered cubic arrangement can be produced with a narrower size distribution which is in marked contrast to commonly observed vertically correlated QDs.
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68.65.Hb Quantum dots (patterned in quantum wells)
68.65.Cd Superlattices
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors

In situ synthesis of In2O3 nanowires with different diameters from indium film

Y. X. Liang, S. Q. Li, L. Nie, Y. G. Wang, and T. H. Wang

Appl. Phys. Lett. 88, 193119 (2006); http://dx.doi.org/10.1063/1.2202192 (3 pages) | Cited 14 times

Online Publication Date: 11 May 2006

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Several kinds of In2O3 nanowires (NWs) with different shapes and diameters were in situ synthesized from indium films with different thicknesses at a low temperature of 400 °C. The NWs had screw structures, and they grew along each axial screw direction by vapor-solid growth mechanism. The thin NWs were synthesized with low indium vapor supersaturation. Two-dimensional nucleation and radial growth trends occurred when the supersaturation increased. The field emission results showed that the turn-on and threshold fields of the thick conical In2O3 NWs were lower than those of the thin ones.
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81.07.Vb Quantum wires
61.46.-w Structure of nanoscale materials
68.65.La Quantum wires (patterned in quantum wells)
81.10.Bk Growth from vapor
81.16.-c Methods of micro- and nanofabrication and processing
79.70.+q Field emission, ionization, evaporation, and desorption

Photoluminescence and Raman scattering studies on PbTiO3 nanowires fabricated by hydrothermal method at low temperature

Yongming Hu, Haoshuang Gu, Xiangcheng Sun, Jing You, and John Wang

Appl. Phys. Lett. 88, 193120 (2006); http://dx.doi.org/10.1063/1.2203736 (3 pages) | Cited 26 times

Online Publication Date: 11 May 2006

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PbTiO3 nanowires have been successfully fabricated by a hydrothermal method at 200 °C. X-ray diffraction result shows that the PbTiO3 nanowires have a tetragonal perovskite structure without any other impurity phase. Scanning electron microscopy and transmission electron microscopy investigations exhibit that the as-prepared samples are made up of large quantity nanowires with diameters of about 10–20 nm and lengths reaching up to 3 μm and single crystalline in nature. Photoluminescence study at room temperature for wavelength between 400 and 650 nm reveals a strong blue-green emission band peaking at ca. 471.4 nm (2.63 eV). Raman spectroscopy study of the nanowires at room temperature demonstrates that the lifetime of the phonons is shorter compare to that of bulk materials.
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81.07.Bc Nanocrystalline materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
61.46.-w Structure of nanoscale materials

Graphitic onions as reaction cells on the nanoscale

L. Sun and F. Banhart

Appl. Phys. Lett. 88, 193121 (2006); http://dx.doi.org/10.1063/1.2202106 (3 pages) | Cited 6 times

Online Publication Date: 11 May 2006

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Multishell fullerene clusters (carbon onions) encapsulating iron crystals of a few nanometers in size are subjected to intense electron irradiation at high temperature in an electron microscope. A reaction between graphite and iron, leading to the formation of iron carbide (cementite) in the core of the clusters, is observed in situ. The reaction in these spherical nanoencapsulates is explained by the occurrence of high pressure, mobile carbon interstitial atoms, and the irradiation-induced lowering of the kinetic barrier. Thus, carbon onions can be used as high-pressure cells for inducing a chemical reaction in nanometer-sized particles.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
61.80.Fe Electron and positron radiation effects
81.05.U- Carbon/carbon-based materials
61.72.J- Point defects and defect clusters

Optical knife-edge technique for nanomechanical displacement detection

D. Karabacak, T. Kouh, C. C. Huang, and K. L. Ekinci

Appl. Phys. Lett. 88, 193122 (2006); http://dx.doi.org/10.1063/1.2203513 (3 pages) | Cited 12 times

Online Publication Date: 11 May 2006

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We describe an optical knife-edge technique for nanomechanical displacement detection. Here, one carefully focuses a laser spot on a moving edge and monitors the reflected power as the edge is displaced sideways. To demonstrate nanomechanical displacement detection using the knife-edge technique, we have measured in-plane resonances of nanometer scale doubly clamped beams. The obtained displacement sensitivity is in the ∼ 1 pm/math range—in close agreement with a simple analytical model.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Thermal decomposition of alkyl monolayers covalently grafted on (111) silicon

A. Faucheux, F. Yang, P. Allongue, C. Henry de Villeneuve, F. Ozanam, and J.-N. Chazalviel

Appl. Phys. Lett. 88, 193123 (2006); http://dx.doi.org/10.1063/1.2202125 (3 pages) | Cited 7 times

Online Publication Date: 12 May 2006

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Alkyl monolayers have been covalently grafted onto atomically flat (111) hydrogenated silicon surfaces through hydrosilylation of 1-alkenes. The thermal stability of the layers under oxidizing or reducing atmospheres has been investigated by quantitative in situ infrared spectroscopy, using a specially designed variable-temperature cell. The layers are thermally stable up to 250 °C. In the range of 250–300 °C, the main reaction is alkene desorption accompanied with silicon oxidation. The characteristic desorption temperature is not significantly affected by changing the atmosphere, the initial packing density of the layers, or the chain length from C18 to C6, but very short chains appear more stable.
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68.43.Mn Adsorption kinetics
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
78.30.-j Infrared and Raman spectra

In situ formation of recombinant humanlike collagen-hydroxyapatite nanohybrid through bionic approach

R. Murugan and S. Ramakrishna

Appl. Phys. Lett. 88, 193124 (2006); http://dx.doi.org/10.1063/1.2202138 (3 pages) | Cited 13 times

Online Publication Date: 12 May 2006

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Processing bone graft materials that mimic the chemical composition and structure of natural bone is a good option for the treatment of bone defects. This investigation reports a processing condition for the in situ formation of recombinant humanlike collagen-hydroxyapatite (CHA) nanohybrid with chemical composition and crystal structure quite similar to natural bone through bionic approach. The processed CHA was characterized by various physicochemical methods and the results suggested that HA crystals are nucleated on the collagen domain with an average size of 32 nm, relatively similar to that of biological apatite. The CHA has enhanced bioresorption than HA and mimics the natural bone in composition and structure; thereby it may be considered for bone applications.
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87.85.J- Biomaterials
87.85.Qr Nanotechnologies-design
87.85.Rs Nanotechnologies-applications
87.14.E- Proteins
82.80.-d Chemical analysis and related physical methods of analysis
61.66.Fn Inorganic compounds

Anomalous positive magnetoresistance at low temperatures in nanocrystalline Ni3Al

A. C. Abhyankar and S. N. Kaul

Appl. Phys. Lett. 88, 193125 (2006); http://dx.doi.org/10.1063/1.2200536 (3 pages) | Cited 4 times

Online Publication Date: 12 May 2006

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Reducing the crystallite size to ≅ 45 nm drives the weak itinerant-electron ferromagnet Ni3Al to magnetic instability, where long-range ferromagnetic order collapses. Non-Fermi-liquid behavior of resistivity, ρ(T), at temperatures 4 K ⩽ T ⩽ 22 K, an abrupt drop in ρ(T), and a sudden increase in positive magnetoresistance at T≲4 K (presumably due to antiferromagnetic-spin fluctuation-mediated superconductivity) in nanocrystalline Ni3Al indicates that the crossover region near the magnetic quantum critical point extends to temperatures as high as 4 K.
Show PACS
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.63.Bd Nanocrystalline materials
61.46.Hk Nanocrystals
72.15.Gd Galvanomagnetic and other magnetotransport effects
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