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17 Sep 2007

Volume 91, Issue 12, Articles (12xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 123101 (2007); http://dx.doi.org/10.1063/1.2784389 (3 pages)

Thierry Laroche, Alexandre Vial, and Matthieu Roussey
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Crystalline structure’s influence on the near-field optical properties of single plasmonic nanowires

Thierry Laroche, Alexandre Vial, and Matthieu Roussey

Appl. Phys. Lett. 91, 123101 (2007); http://dx.doi.org/10.1063/1.2784389 (3 pages) | Cited 11 times

Online Publication Date: 17 September 2007

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The finite difference time domain method is employed to study the crystalline structure’s influence on the propagation of a local excitation along metallic nanowires of subwavelength cross section. The metallic nanowires are elongated cylinders deposited on a transparent substrate. A tightly focused gaussian beam illuminates one end of the nanowires. According to recent experimental studies, the authors show that the propagation length of the localized surface plasmon excitations depends on the crystalline structure of the nanowire. Thus, they are able to determine the effective permittivity of metals in such a nanostructure versus its crystalline properties. The authors also demonstrate that the field of optical information transport could greatly benefit from the care of the subwavelength optical waveguide’s crystallinity.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.Hk Nanocrystals
73.22.Lp Collective excitations
77.22.Ch Permittivity (dielectric function)
42.79.Gn Optical waveguides and couplers

Nanoscale ablation on patterned diamondlike carbon film with femtosecond laser pulses

Godai Miyaji and Kenzo Miyazaki

Appl. Phys. Lett. 91, 123102 (2007); http://dx.doi.org/10.1063/1.2784966 (3 pages) | Cited 15 times

Online Publication Date: 17 September 2007

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The authors have studied the origin of nanostructure formation on diamondlike carbon film in femtosecond laser ablation at low fluence. Using the thin film target patterned with submicrometer-size stripes, they have observed that the nanostructure starts to be formed on the crest of stripes along the direction perpendicular to the laser polarization. The experimental results have shown that nanoscale ablation for the nanostructuring would preferentially be initiated by the enhancement of localized electric field on the stripe surface with high curvature.
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81.07.Bc Nanocrystalline materials
81.16.Rf Micro- and nanoscale pattern formation
42.62.-b Laser applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
61.46.Hk Nanocrystals

Controlled synthesis of lanthanide-doped NaYF4 upconversion nanocrystals via ligand induced crystal phase transition and silica coating

Jingning Shan and Yiguang Ju

Appl. Phys. Lett. 91, 123103 (2007); http://dx.doi.org/10.1063/1.2783476 (3 pages) | Cited 45 times

Online Publication Date: 18 September 2007

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Upconversion nanocrystals (NCs) of NaYF4:Yb,Ln (Ln = Er and Tm) in cubic and hexagonal phases were synthesized in oleic acid (OA) and/or trioctylphosphine (TOP) with octadecene (ODE) via a thermolysis method. Only cubic-phase NCs were obtained in OA/ODE and TOP/ODE solvents; on the other hand, the hexagonal-phase NCs resulted in OA/TOP/ODE. The phase transition from cubic to hexagonal was induced by a ligand formed between oleate and TOP at high temperature. Moreover, the addition of OA/TOP in high and low ratios produced hexagonal nanoparticles and nanorods, respectively. The formed NCs were coated by SiO2 using microemulsion reactions for further biofunctionalization in biological applications.
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81.07.Bc Nanocrystalline materials
71.70.Ch Crystal and ligand fields
64.70.Nd Structural transitions in nanoscale materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.16.-c Methods of micro- and nanofabrication and processing
81.20.-n Methods of materials synthesis and materials processing

Electrical conduction of Ge nanodot arrays formed on an oxidized Si surface

Yasuo Nakayama, Shiro Yamazaki, Hiroyuki Okino, Toru Hirahara, Iwao Matsuda, Shuji Hasegawa, and Masakazu Ichikawa

Appl. Phys. Lett. 91, 123104 (2007); http://dx.doi.org/10.1063/1.2784181 (3 pages) | Cited 6 times

Online Publication Date: 18 September 2007

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Carrier transport mechanism on Ge nanodot arrays formed on SiO2 monolayer covering over the Si surface is investigated by microscopic four-point-probe measurements combined with core-level photoemission spectroscopy and scanning tunneling microscopy. Different conduction natures are found depending on whether or not the nanodots and the substrate are directly connected by subnanometer-sized voids penetrating the SiO2 layer. In the presence of the voids, conductivity is regulated by the dot-size through quantum-size effect.
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73.63.Kv Quantum dots
73.21.La Quantum dots
73.61.Cw Elemental semiconductors

Gate-tunable graphene spin valve

Sungjae Cho, Yung-Fu Chen, and Michael S. Fuhrer

Appl. Phys. Lett. 91, 123105 (2007); http://dx.doi.org/10.1063/1.2784934 (3 pages) | Cited 87 times

Online Publication Date: 19 September 2007

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The authors perform nonlocal four-probe spin-valve experiments on graphene contacted by ferromagnetic Permalloy electrodes. They observe sharp switching and often sign reversal of the nonlocal resistance at the coercive field of the electrodes, indicating the presence of a spin current between injector and detector. The nonlocal spin-valve signal changes magnitude and sign with back-gate voltage, and is observed up to T = 300 K. The gate voltage variation of the spin-valve signal may result from quantum-coherent transport, as evidenced by Fabry-Pérot-like oscillations of the current.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices

Analytical formulas and scaling laws for peak interaction forces in dynamic atomic force microscopy

Shuiqing Hu and Arvind Raman

Appl. Phys. Lett. 91, 123106 (2007); http://dx.doi.org/10.1063/1.2783226 (3 pages) | Cited 15 times

Online Publication Date: 19 September 2007

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Determining the peak interaction force between an oscillating nanoscale tip and a sample surface has been a fundamental yet elusive goal in amplitude-modulated atomic force microscopy. Closed form analytical expressions are derived using nonlinear asymptotic theory for the peak attractive and repulsive forces that approximate with a high degree of accuracy the numerically simulated peak forces under ambient or vacuum conditions. Scaling laws involving van der Waals, chemical forces, nanoscale elasticity, and oscillator parameters are identified to demonstrate approximate similitude for the peak interaction forces under practical operating conditions.
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68.37.Ps Atomic force microscopy (AFM)

Concerning the 506 cm−1 band in the Raman spectrum of silicon nanowires

J. D. Prades, J. Arbiol, A. Cirera, J. R. Morante, and A. Fontcuberta i Morral

Appl. Phys. Lett. 91, 123107 (2007); http://dx.doi.org/10.1063/1.2786606 (3 pages) | Cited 10 times

Online Publication Date: 19 September 2007

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Silicon nanowires synthesized on an amorphous substrate by the vapor-liquid-solid method were studied using Raman spectroscopy and ab initio calculations. The authors show that the Raman spectrum of Si nanowires is compatible with the existence of two distinct phases. The Raman spectra revealed a peak centered around 517 cm−1 as expected for the nanosized diamond cubic phase (Si-I). However, two new contributions, centered around 506 and 516 cm−1, arose which they attributed to the diamond hexagonal phase (Si-IV). The identification of these Raman peaks clarifies the controversy surrounding the vibration modes of Si-IV previously reported in the literature.
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78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
71.15.-m Methods of electronic structure calculations

Focused ion beam implantation induced site-selective growth of InAs quantum dots

M. Mehta, D. Reuter, A. Melnikov, A. D. Wieck, and A. Remhof

Appl. Phys. Lett. 91, 123108 (2007); http://dx.doi.org/10.1063/1.2786836 (3 pages) | Cited 21 times

Online Publication Date: 20 September 2007

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The site-selective growth of InAs quantum dots (QDs) by a combined focused ion beam (FIB) and molecular beam epitaxy (MBE) process has been demonstrated. An array of FIB modified spots on MBE grown GaAs was fabricated. Thereafter, an in situ annealing step followed by InAs deposition was performed. The InAs QDs were preferentially formed in the holes generated by the FIB. The influences of ion dose, annealing parameters, and InAs amount were investigated. With optimized parameters, the authors observe more than 50% single dot occupancy per holes. Photoluminescence spectra confirm the good optical quality of the QDs.
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81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Near ultraviolet light emitting diode composed of n-GaN/ZnO coaxial nanorod heterostructures on a p-GaN layer

Sung Jin An and Gyu-Chul Yi

Appl. Phys. Lett. 91, 123109 (2007); http://dx.doi.org/10.1063/1.2786852 (3 pages) | Cited 16 times

Online Publication Date: 20 September 2007

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The authors report on the fabrication and characteristics of near ultraviolet nanorod light emitting diodes (LEDs) composed of n-GaN/ZnO nanorod heterostructures on p-GaN substrates. The nanorod LEDs consist of the vertically aligned n-GaN/ZnO coaxial nanorod arrays grown on a p-GaN substrate. The LEDs demonstrated strong near ultraviolet emission at room temperature. The nanorod LEDs were turned on a forward-bias voltage of 5 V, and exhibited a large light emitting area. From electroluminescent spectra, dominant emission peaks were observed at 2.96 and 3.24 eV for an applied current of 2 mA. The origins of the strong and large area light emission are also discussed in terms of enhanced carrier injection from n-GaN nanostructures to p-GaN substrates.
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85.60.Jb Light-emitting devices
42.79.Kr Display devices, liquid-crystal devices

Magnetothermopower and magnetoresistivity of RuSr2Gd2−xCexCu2O10+δ (x = 0.6,1.0)

Chia-Jyi Liu, Pradipta K. Nayak, and G. V. M. Williams

Appl. Phys. Lett. 91, 123110 (2007); http://dx.doi.org/10.1063/1.2784962 (3 pages) | Cited 6 times

Online Publication Date: 20 September 2007

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We report measurements of magnetothermopower and magnetoresistivity as a function of temperature on RuSr2Gd2−xCexCu2O10+δ (x = 0.6,1). In a magnetic field of 5 T, the size of thermopower decreases significantly, whereas the normal-state resistivity decreases slightly, which behaves similarly to RuSr2Gd1−xLaxCu2O8 (x = 0,0.1). A significant decrease of thermopower for both samples could be attributed to the decrease of the spin entropy contribution associated with the carriers in the RuO2 layers, as the Ru moments are aligned with the magnetic field. It is also found that the nonmetallic temperature dependence at low T follows a variable range hopping process for both samples.
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74.72.-h Cuprate superconductors
74.25.F- Transport properties
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Bt Thermodynamic properties

Atomic force microscope based nanofabrication of master pattern molds for use in soft lithography

Matthew S. Johannes, Daniel G. Cole, and Robert L. Clark

Appl. Phys. Lett. 91, 123111 (2007); http://dx.doi.org/10.1063/1.2787965 (3 pages)

Online Publication Date: 20 September 2007

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The authors have developed a technique that couples nanolithographic patterning using an atomic force microscope with the parallel patterning abilities of soft lithography. Master pattern generation is accomplished using local anodic oxidation as a mask pattern for anisotropic wet etching of Si(110). The resulting nanostructures are then used as master patterns for the molding of polymeric stamps to be used for microcontact printing of alkanethiols. Analysis of the resulting patterns demonstrates the validity of this method as a simple, effective, and low cost alternative to conduct and prototype nanoscale patterning in a parallel fashion.
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81.16.Ta Atom manipulation
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
68.37.Ps Atomic force microscopy (AFM)

Spectral sensitivity of two-dimensional nanohole array surface plasmon polariton resonance sensor

Lin Pang, Grace M. Hwang, Boris Slutsky, and Yeshaiahu Fainman

Appl. Phys. Lett. 91, 123112 (2007); http://dx.doi.org/10.1063/1.2789181 (3 pages) | Cited 54 times

Online Publication Date: 20 September 2007

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An analytical expression of spectral sensitivity derived from a surface plasmon polariton dispersion relation for a two-dimensional nanohole array surface plasmon polariton resonance sensor is presented. The sensitivity of the nanohole array sensor depends on the periodicity of the array and the order of the excited surface plasmon polariton modes. The analytical expression is further confirmed by rigorous electromagnetic simulation and validated by experimental results. Real-time monitoring of protein-protein specific bonding is performed to demonstrate the integrated microfluidic nanohole array surface plasmon resonance biosensor.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
87.80.-y Biophysical techniques (research methods)
87.14.E- Proteins
87.15.B- Structure of biomolecules
36.20.Hb Configuration (bonds, dimensions)

Patterning of silicon by indentation and chemical etching

R. Rao, J. E. Bradby, and J. S. Williams

Appl. Phys. Lett. 91, 123113 (2007); http://dx.doi.org/10.1063/1.2779111 (3 pages) | Cited 6 times

Online Publication Date: 20 September 2007

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An array of features on Si (100) is fabricated by a new maskless pattering process involving a combination of indentation and anisotropic wet chemical etching. Indentation is carried out in order to induce transformation to the high-pressure phases, Si III and Si XII, before etching in a KOH solution. The pressure-induced phases are found to be highly resistant to etching in the KOH solution, with an etch rate more than an order of magnitude slower than that of Si (100). The possibility of exploiting this mechanism for a maskless nanoscale patterning process in Si using indentation is discussed.
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81.16.Rf Micro- and nanoscale pattern formation
64.70.K- Solid-solid transitions
81.65.Cf Surface cleaning, etching, patterning

Magnetic field driven nanowire rotation in suspension

K. Keshoju, H. Xing, and L. Sun

Appl. Phys. Lett. 91, 123114 (2007); http://dx.doi.org/10.1063/1.2789184 (3 pages) | Cited 18 times

Online Publication Date: 20 September 2007

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Magnetic field driven nanowire rotation in liquids has been investigated. This approach provides a noncontact, sensitive, cost effective, and easy to scale up scenario to manipulate the motion of magnetized one-dimensional nanostructures for “nanomachine” and anisotropic nanomaterial development. Due to the small dimensions, viscous behavior dominates the nanowire motion. Qualitative analyses considering the competing magnetic field induced torque and resisting fluid drag torque have been conducted for nanowire rotation under different circumstances. The analyses and experimental observations can provide key information for the understanding of hydrodynamics at the nanoscale.
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47.85.Np Fluidics
66.20.-d Viscosity of liquids; diffusive momentum transport
47.65.-d Magnetohydrodynamics and electrohydrodynamics

Enhanced spontaneous emission rate from single InAs quantum dots in a photonic crystal nanocavity at telecom wavelengths

L. Balet, M. Francardi, A. Gerardino, N. Chauvin, B. Alloing, C. Zinoni, C. Monat, L. H. Li, N. Le Thomas, R. Houdré, and A. Fiore

Appl. Phys. Lett. 91, 123115 (2007); http://dx.doi.org/10.1063/1.2789291 (3 pages) | Cited 11 times

Online Publication Date: 20 September 2007

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The authors demonstrate coupling at 1.3 μm between single InAs quantum dots (QDs) and a mode of a two dimensional photonic crystal (PhC) defect cavity with a quality factor of 15 000. By spectrally tuning the cavity mode, they induce coupling with excitonic lines. They perform a time integrated and time-resolved photoluminescence and measure an eightfold increase in the spontaneous emission rate inducing a coupling efficiency of 96%. These measurements indicate the potential of single QDs in PhC cavities as efficient single-photon emitters for fiber-based quantum information processing applications.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
42.70.Qs Photonic bandgap materials
68.65.Hb Quantum dots (patterned in quantum wells)

Electron transport and recombination in polycrystalline TiO2 nanowire dye-sensitized solar cells

Emil Enache-Pommer, Janice E. Boercker, and Eray S. Aydil

Appl. Phys. Lett. 91, 123116 (2007); http://dx.doi.org/10.1063/1.2783477 (3 pages) | Cited 49 times

Online Publication Date: 20 September 2007

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Electron transport and recombination time constants in dye-sensitized solar cells made from TiO2 nanowires were determined using transient photocurrent and photovoltage measurements. The magnitude of the electron transport time (10−2 to 10−3 s) and its dependence on the illumination intensity were similar to those reported for dye-sensitized solar cells made from TiO2 nanoparticles indicating that electron capture and release by surface traps determine transport times even in nanowires. However, the ratio of the electron recombination time to the electron collection time in nanowire solar cells was ∼ 150, larger than those observed in nanoparticle dye-sensitized solar cells.
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84.60.Jt Photoelectric conversion
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Anisotropy of light extraction from two-dimensional photonic crystal light-emitting diodes

Chun-Feng Lai, H. C. Kuo, C. H. Chao, H. T. Hsueh, J.-F. T. Wang, W. Y. Yeh, and J. Y. Chi

Appl. Phys. Lett. 91, 123117 (2007); http://dx.doi.org/10.1063/1.2789399 (3 pages) | Cited 14 times

Online Publication Date: 20 September 2007

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Anisotropic light extraction of photonic crystal (PhC) light-emitting diodes in the azimuthal direction has been investigated with an annular structure of triangular PhC lattice. The optical images of the photoluminescence light extraction are obtained with laser excitation. For increasing lattice constant, sixfold symmetric patterns with varying numbers of petals in multiples of six are observed and analyzed. A map of the anisotropy for various lattice constants and numerical apertures is constructed. Several features of light propagations associated with the PhC are observed including the focusing and collimating behaviors.
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85.60.Jb Light-emitting devices
42.70.Qs Photonic bandgap materials
78.55.-m Photoluminescence, properties and materials

Fabrication of complex nanoscale structures on various substrates

Kang-Soo Han, Sung-Hoon Hong, and Heon Lee

Appl. Phys. Lett. 91, 123118 (2007); http://dx.doi.org/10.1063/1.2789735 (3 pages) | Cited 7 times

Online Publication Date: 20 September 2007

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Polymer based complex nanoscale structures were fabricated and transferred to various substrates using reverse nanoimprint lithography. To facilitate the fabrication and transference of the large area of the nanostructured layer to the substrates, a water-soluble polyvinyl alcohol mold was used. After generation and transference of the nanostructured layer, the polyvinyl alcohol mold was removed by dissolving in water. A residue-free, UV-curable, glue layer was formulated and used to bond the nanostructured layer onto the substrates. As a result, nanometer scale patterned polymer layers were bonded to various substrates and three-dimensional nanostructures were also fabricated by stacking of the layers.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Nd Micro- and nanolithography
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.41.+e Polymers, elastomers, and plastics
61.46.-w Structure of nanoscale materials
82.35.-x Polymers: properties; reactions; polymerization

Length-dependent thermal conductivity of an individual single-wall carbon nanotube

Zhao Liang Wang, Da Wei Tang, Xiao Bo Li, Xing Hua Zheng, Wei Gang Zhang, Li Xin Zheng, Yuntian T. Zhu, Ai Zi Jin, Hai Fang Yang, and Chang Zhi Gu

Appl. Phys. Lett. 91, 123119 (2007); http://dx.doi.org/10.1063/1.2779850 (3 pages) | Cited 26 times

Online Publication Date: 21 September 2007

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The thermal conductivity of single-wall carbon nanotubes (SWCNTs) is predicted to increase with length, but this has never been proved experimentally because of limitations in previous measurement methods. Here, the authors report the measurement of the length-dependent thermal conductivities of individual SWCNTs on a Si substrate using a four-pad 3ω method. An increase in thermal conductivity with length was observed at room temperature, which is consistent with a theoretical prediction that considers higher order three-phonon processes. When SWCNTs are longer than the phonon mean path, they showed dissipative thermal transport. The observed increase of thermal conductivity with length makes SWCNTs ideal for thermal management.
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73.63.Fg Nanotubes
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Controlled fabrication of 1–2 nm nanogaps by electromigration in gold and gold-palladium nanowires

F. O. Hadeed and C. Durkan

Appl. Phys. Lett. 91, 123120 (2007); http://dx.doi.org/10.1063/1.2785982 (3 pages) | Cited 12 times

Online Publication Date: 21 September 2007

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The authors report the electrical characterization of gold and gold-palladium nanowires failed by electromigration. Nanogaps 1–2 nm in size are reliably made from metal nanowires by controlling the electromigration failure process, opening up the possibility of using these metal nanowires with nanogaps for molecular conduction studies and large-scale molecular junction device fabrication. Nanogaps are formed by applying a voltage sweep to the wires at a ramp rate of 4 mV/s. The interplay between Joule heating and electromigration means that reliable nanogaps can be formed without the need of a feedback circuit, rendering the technique relatively simple to implement.
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81.07.Lk Nanocontacts
66.30.Qa Electromigration

Measuring the mass, density, and size of particles and cells using a suspended microchannel resonator

Michel Godin, Andrea K. Bryan, Thomas P. Burg, Ken Babcock, and Scott R. Manalis

Appl. Phys. Lett. 91, 123121 (2007); http://dx.doi.org/10.1063/1.2789694 (3 pages) | Cited 26 times

Online Publication Date: 21 September 2007

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We demonstrate the measurement of mass, density, and size of cells and nanoparticles using suspended microchannel resonators. The masses of individual particles are quantified as transient frequency shifts, while the particles transit a microfluidic channel embedded in the resonating cantilever. Mass histograms resulting from these data reveal the distribution of a population of heterogeneously sized particles. Particle density is inferred from measurements made in different carrier fluids since the frequency shift for a particle is proportional to the mass difference relative to the displaced solution. We have characterized the density of polystyrene particles, Escherichia coli, and human red blood cells with a resolution down to 10−4 g/cm3.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
06.30.Dr Mass and density
07.10.Cm Micromechanical devices and systems
47.80.-v Instrumentation and measurement methods in fluid dynamics

Spatial imaging of modifications to fluorescence lifetime and intensity by individual Ag nanoparticles

T. Ritman-Meer, N. I. Cade, and D. Richards

Appl. Phys. Lett. 91, 123122 (2007); http://dx.doi.org/10.1063/1.2789700 (3 pages) | Cited 11 times

Online Publication Date: 21 September 2007

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Highly ordered periodic arrays of silver nanoparticles have been fabricated which exhibit surface plasmon resonances in the visible spectrum. We demonstrate the ability of these structures to alter the fluorescence properties of vicinal dye molecules by providing an additional radiative decay channel. Using fluorescence lifetime imaging microscopy, we have created high resolution spatial maps of the molecular lifetime components; these show an order of magnitude increase in decay rate from a localized volume around the nanoparticles, resulting in a commensurate enhancement in the fluorescence emission intensity.
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78.55.Hx Other solid inorganic materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.22.Lp Collective excitations

Evidence for strong Fermi-level pinning due to metal-induced gap states at metal/germanium interface

Tomonori Nishimura, Koji Kita, and Akira Toriumi

Appl. Phys. Lett. 91, 123123 (2007); http://dx.doi.org/10.1063/1.2789701 (3 pages) | Cited 58 times

Online Publication Date: 21 September 2007

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The purpose of this paper is to understand metal/germanium (Ge) junction characteristics. Electrode metals with a wide work function range were deposited on Ge. All metal/p-Ge and metal/n-Ge junctions have shown Ohmic and Schottky characteristics, respectively, with the strong Fermi-level pinning. The charge neutrality level (CNL) at metal/Ge interface is close to the branch point calculated for the bulk Ge. Moreover, the pinning level is hardly modulated by annealing in forming gas, forming metal-germanide/Ge interfaces or changing the substrate orientation. These results suggest that Fermi level at metal/Ge interface is intrinsically pinned at the CNL characterized by the metal-induced gap states model.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
71.20.-b Electron density of states and band structure of crystalline solids

Intrusion-type deformation in epitaxial Ti3SiC2/TiC0.67 nanolaminates

O. Wilhelmsson, P. Eklund, F. Giuliani, H. Högberg, L. Hultman, and U. Jansson

Appl. Phys. Lett. 91, 123124 (2007); http://dx.doi.org/10.1063/1.2789710 (3 pages) | Cited 7 times

Online Publication Date: 21 September 2007

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We investigate the deformation of epitaxial Ti3SiC2(0001)/TiCx(111) (x ∼ 0.67) nanolaminates deposited by magnetron sputtering. Nanoindentation and transmission electron microscopy show that the Ti3SiC2 layers deform via basal plane slip and intrusion into the TiC layers, suppressing kink-band and pile-up deformation behaviors analogous with monolithic Ti3SiC2. This remarkable response to indentation is due to persistent slip in the TiC layers and prevention of gross slip throughout the nanolaminate by the interleaving Ti3SiC2 layers. Hardness and Young’s modulus were measured as ∼ 15 and ∼ 240 GPa, respectively.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.37.Lp Transmission electron microscopy (TEM)
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