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13 Aug 2007

Volume 91, Issue 7, Articles (07xxxx)

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Appl. Phys. Lett. 91, 071906 (2007); http://dx.doi.org/10.1063/1.2753092 (3 pages)

Cheng Zhang, Rajiv K. Kalia, Aiichiro Nakano, and Priya Vashishta
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Anchoring phthalocyanine molecules on the 6H‐SiC(0001)3×3 surface

G. Baffou, A. J. Mayne, G. Comtet, G. Dujardin, Ph. Sonnet, and L. Stauffer

Appl. Phys. Lett. 91, 073101 (2007); http://dx.doi.org/10.1063/1.2769761 (3 pages) | Cited 3 times

Online Publication Date: 13 August 2007

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The adsorption of individual metal-free phthalocyanine molecules on the 6H‐SiC(0001)3×3 surface was studied using the scanning tunneling microscope supported by density functional theory calculations. Phthalocyanine molecules were found to be chemisorbed through a reaction of two conjugated imide groups with two silicon adatoms. This type of anchoring opens numerous perspectives for the organic functionalization of a biocompatible wide band gap semiconductor.
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68.43.Mn Adsorption kinetics
68.43.Fg Adsorbate structure (binding sites, geometry)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Branched growth of degenerately Sb-doped SnO2 nanowires

Jin Huang, Aixia Lu, Bin Zhao, and Qing Wan

Appl. Phys. Lett. 91, 073102 (2007); http://dx.doi.org/10.1063/1.2769756 (3 pages) | Cited 12 times

Online Publication Date: 13 August 2007

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The authors report the growth of degenerately Sb-doped SnO2 single crystalline nanowires with three-dimensionally branched morphology by a two-step Au-catalyzed vapor-liquid-solid growth approach. Raman scattering and transmission electron microscopy results indicate that the crystal phase of Sb-doped SnO2 nanowires is rutile. Electrical transport measurements indicate that Sb-doped SnO2 nanowire has a resistivity of 1.92×10−3 Ω cm and an electron concentration of 2.8×1020 cm3. Branched conducting nanowires are promising candidates for catalyst supports, biologic molecule detection, and three-dimensional nanodevices integration.
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81.07.Vb Quantum wires
81.16.-c Methods of micro- and nanofabrication and processing
68.65.La Quantum wires (patterned in quantum wells)
78.67.Lt Quantum wires
73.63.Nm Quantum wires
61.72.up Other materials

Effect of edge roughness in graphene nanoribbon transistors

Youngki Yoon and Jing Guo

Appl. Phys. Lett. 91, 073103 (2007); http://dx.doi.org/10.1063/1.2769764 (3 pages) | Cited 36 times

Online Publication Date: 13 August 2007

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The effects of edge irregularity and mixed-edge shapes on the characteristics of graphene nanoribbon transistors are examined by self-consistent atomistic simulations based on the nonequilibrium Green’s function formalism. The minimal leakage current increases due to the localized states induced in the band gap, and the on current decreases due to smaller quantum transmission and the self-consistent electrostatic effect in general. Although the ratio between the on current and minimal leakage current decreases, the transistor still switches even in the presence of edge roughness. The variation between devices, however, can be large, especially for a short channel length.
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85.30.Tv Field effect devices
85.35.-p Nanoelectronic devices

Anomalous photoconductivity of CeO2 nanowires in air

X. Q. Fu, C. Wang, P. Feng, and T. H. Wang

Appl. Phys. Lett. 91, 073104 (2007); http://dx.doi.org/10.1063/1.2771090 (3 pages) | Cited 10 times

Online Publication Date: 14 August 2007

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The conductance of the CeO2 nanowire film is found to decrease by about two orders of magnitude in air under ultraviolet illumination. Such a drastic decrease in conductance is attributed to light-induced desorption of H2O from the nanowire’s surface. When exposed in air, the surface conductivity of the nanowire increases significantly due to the adsorption of H2O. Considering the large surface-to-volume ratio of the nanowire, the conductance of the nanowire film is mainly controlled by surface conduction. Upon ultraviolet illumination, desorption of H2O results in the decrease of the conductance of the nanowire film, thus leading to the anomalous photoconductivity.
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73.63.Nm Quantum wires
73.50.Pz Photoconduction and photovoltaic effects
73.25.+i Surface conductivity and carrier phenomena
68.43.Mn Adsorption kinetics

Modified effective medium formulation for the thermal conductivity of nanocomposites

Austin Minnich and Gang Chen

Appl. Phys. Lett. 91, 073105 (2007); http://dx.doi.org/10.1063/1.2771040 (3 pages) | Cited 44 times

Online Publication Date: 14 August 2007

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This letter introduces a modified effective medium formulation for composites where the characteristic length of the inclusion is on the order of or smaller than the phonon mean free path. The formulation takes into account the increased interface scattering in the different phases of the nanocomposite and the thermal boundary resistance between the phases. The interface density of inclusions is introduced and is found to be a primary factor in determining the thermal conductivity. The predictions are in good agreement with results from Monte Carlo simulations and solutions to the Boltzmann equation.
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72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
61.72.Qq Microscopic defects (voids, inclusions, etc.)
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Double capping of molecular beam epitaxy grown InAs/InP quantum dots studied by cross-sectional scanning tunneling microscopy

J. M. Ulloa, P. M. Koenraad, E. Gapihan, A. Létoublon, and N. Bertru

Appl. Phys. Lett. 91, 073106 (2007); http://dx.doi.org/10.1063/1.2771063 (3 pages) | Cited 9 times

Online Publication Date: 15 August 2007

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Cross-sectional scanning tunneling microscopy was used to study at the atomic scale the double capping process of self-assembled InAs/InP quantum dots (QDs) grown by molecular beam epitaxy on a (311)B substrate. The thickness of the first capping layer is found to play a mayor role in determining the final results of the process. For first capping layers up to 3.5 nm, the height of the QDs correspond to the thickness of the first capping layer. Nevertheless, for thicknesses higher than 3.5 nm, a reduction in the dot height compared to the thickness of the first capping layer is observed. These results are interpreted in terms of a transition from a double capping to a classical capping process when the first capping layer is thick enough to completely cover the dots.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.16.Dn Self-assembly

Heat treatment parameters effecting the fractal dimensions of AuGe metallization on GaAs

Imre Mojzes, Csaba Dominkovics, Gábor Harsányi, Szilvia Nagy, János Pipek, and László Dobos

Appl. Phys. Lett. 91, 073107 (2007); http://dx.doi.org/10.1063/1.2768911 (3 pages)

Online Publication Date: 16 August 2007

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Correlation was detected between the thermal treatment parameters of the AuGe–GaAs system and surface fractal structure. Structural entropic calculations were used to confirm the results obtained by fractal calculations.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Gh Other heat and thermomechanical treatments

Self-seeded growth and ultraviolet photoresponse properties of ZnO nanowire arrays

R. Ghosh, M. Dutta, and D. Basak

Appl. Phys. Lett. 91, 073108 (2007); http://dx.doi.org/10.1063/1.2771533 (3 pages) | Cited 30 times

Online Publication Date: 16 August 2007

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The authors report on the self-seeded growth of ZnO nanowire (NW) arrays on glass substrates by a simple solvothermal method using two different sol concentrations for the seed layer formation. The formations of hexagonal-shaped NWs with diameter of 20–60 nm on the seed layer for 0.1M sol and mostly of trapezoidal-shaped NWs with base width of 135 nm on the seed layer for 0.03M sol have been explained considering the longitudinal and transversal growths of ZnO NWs. The photocurrent behavior of ZnO NW arrays in air as well as in vacuum is analyzed in terms of adsorbed oxygen and water molecules.
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81.16.-c Methods of micro- and nanofabrication and processing
81.10.Dn Growth from solutions
61.46.-w Structure of nanoscale materials
73.63.-b Electronic transport in nanoscale materials and structures
68.43.Mn Adsorption kinetics

High-speed growth and photoluminescence of porous anodic alumina films with controllable interpore distances over a large range

Y. B. Li, M. J. Zheng, and L. Ma

Appl. Phys. Lett. 91, 073109 (2007); http://dx.doi.org/10.1063/1.2772184 (3 pages) | Cited 19 times

Online Publication Date: 16 August 2007

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Highly ordered porous anodic alumina (PAA) films are fabricated with high efficiency by stable high-field anodization in oxalic acid/ethanol/water electrolytes at 100–180 V and sulfuric acid/oxalic acid/ethanol/water electrolytes at 30–80 V, giving interpore distances in the range of 225–450 nm and 70–140 nm, respectively. The photoluminescence of PAA films prepared by high-field anodization shows remarkable redshift of the peak position and decrease of the intensity compared to that of PAA films formed by conventional low-field anodization.
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78.55.Mb Porous materials
82.45.Cc Anodic films
82.45.Gj Electrolytes

Laser assisted field induced oxide nanopatterning of hydrogen passivated silicon surfaces

L. S. C. Pingree, M. J. Schmitz, D. E. Kramer, and M. C. Hersam

Appl. Phys. Lett. 91, 073110 (2007); http://dx.doi.org/10.1063/1.2771061 (3 pages) | Cited 2 times

Online Publication Date: 17 August 2007

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Field induced oxide (FIO) nanopatterning of hydrogen passivated silicon surfaces with an atomic force microscope (AFM) has been controlled by laser irradiation. Specifically, local oxidation on H:Si(111) surfaces can be fully suppressed or activated by toggling a laser that is illuminating a lightly doped silicon AFM cantilever. The nanopatterning mechanism is attributed to the control of the free carrier concentration in the AFM probe by the laser. When the laser is toggled off, charge injection is terminated, thus eliminating the electrochemical reactions required for oxide formation. Laser assisted FIO provides an alternative and flexible means for controlling oxide nanopatterning.
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81.05.Cy Elemental semiconductors
81.16.Rf Micro- and nanoscale pattern formation
81.65.Rv Passivation
81.65.Mq Oxidation
68.37.Ps Atomic force microscopy (AFM)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
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