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17 Oct 2005

Volume 87, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 161907 (2005); http://dx.doi.org/10.1063/1.2105998 (3 pages)

J. Das, K. B. Kim, F. Baier, W. Löser, and J. Eckert
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Growth of light-emitting silicate nanowires on individual Au particles in self-assembled hexagonal Au particle networks

P. Y. Su, M. Y. Lu, J. C. Hu, S. L. Cheng, L. J. Chen, and J. M. Liang

Appl. Phys. Lett. 87, 163101 (2005); http://dx.doi.org/10.1063/1.2093939 (3 pages) | Cited 8 times

Online Publication Date: 10 October 2005

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Hierarchical growth of silicate nanowires on individual Au particles in self-organized hexagonal Au particle networks has been achieved by appropriate control of annealing conditions in N2 ambient. Cathodoluminescence data showed that the silicate nanowires emit light with a wavelength of 415 nm. The scheme to form the regular Au particle network offers an effective and economical means to produce a universal template to grow functional structures without complex lithography.
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81.07.Bc Nanocrystalline materials
81.16.Dn Self-assembly
68.65.La Quantum wires (patterned in quantum wells)
78.60.Hk Cathodoluminescence, ionoluminescence
81.40.Gh Other heat and thermomechanical treatments

Large-sized tubular graphite cones with nanotube tips

N. G. Shang and X. Jiang

Appl. Phys. Lett. 87, 163102 (2005); http://dx.doi.org/10.1063/1.2093919 (3 pages) | Cited 5 times

Online Publication Date: 10 October 2005

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Tubular graphite cones (TGCs) have been grown on planar steel substrates by microwave plasma-assisted chemical vapor deposition with a high concentration of methane and at a high substrate temperature. The largest TGCs can reach 110 μm in length and 10 μm in diameter at the root. Unique TGCs terminated in long extruding carbon nanotube tips are realized. Scanning micro-Raman spectroscopy of individual TGCs shows a high crystallinity of the tips and more disordered structure of the roots. A possible growth mechanism of TGCs is presented.
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81.05.U- Carbon/carbon-based materials
81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.Ch Nanotubes
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.65.La Quantum wires (patterned in quantum wells)
78.30.Na Fullerenes and related materials

Nanostructured stars of ZnO microcrystals with intense stimulated emission

Yuzhen Lv, Chunping Li, Lin Guo, Qingxiao Wang, Rongming Wang, Huibin Xu, Shihe Yang, Xicheng AI, and Jianping Zhang

Appl. Phys. Lett. 87, 163103 (2005); http://dx.doi.org/10.1063/1.2093933 (3 pages) | Cited 10 times

Online Publication Date: 10 October 2005

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We demonstrate the synthesis of single-crystalline star-shaped ZnO microcrystals with six arms by a simple solution method. Microscopic and diffraction data reveal that the as-grown products have a wurtzite structure. Each arm of the ZnO microstars has a sharp tip of several nanometers. Under moderate optical excitation, stimulated emission was observed at 388.4 nm with a full width at half-maximum (FWHM) of less than 3 nm and a threshold of 318 kW/cm2.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
78.45.+h Stimulated emission
68.37.Lp Transmission electron microscopy (TEM)

Real-time x-ray studies of Mo-seeded Si nanodot formation during ion bombardment

Gozde Ozaydin, Ahmet S. Özcan, Yiyi Wang, Karl F. Ludwig, Hua Zhou, Randall L. Headrick, and D. Peter Siddons

Appl. Phys. Lett. 87, 163104 (2005); http://dx.doi.org/10.1063/1.2099521 (3 pages) | Cited 38 times

Online Publication Date: 10 October 2005

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The formation of self-organized Si nanostructures induced by Mo seeding during normal incidence Ar+ ion bombardment at room temperature is reported. Silicon surfaces without Mo seeding develop only power-law roughness during 1000 eV ion bombardment at normal incidence, in agreement with scaling theory expectations of surface roughening. However, supplying Mo atoms to the surface during ion bombardment seeds the development of highly correlated, nanoscale structures (“dots”) that are typically 3 nm high with a spatial wavelength of approximately 30 nm. With time, these saturate and further surface roughening is dominated by the growth of long-wavelength corrugations.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
81.07.Bc Nanocrystalline materials
68.47.Fg Semiconductor surfaces
81.16.Dn Self-assembly
81.05.Cy Elemental semiconductors
78.70.Ck X-ray scattering
61.80.Jh Ion radiation effects
68.35.B- Structure of clean surfaces (and surface reconstruction)

Lens-shaped all-epitaxial quantum dot microcavity

D. Lu, J. Ahn, S. Freisem, D. Gazula, and D. G. Deppe

Appl. Phys. Lett. 87, 163105 (2005); http://dx.doi.org/10.1063/1.2099525 (3 pages) | Cited 9 times

Online Publication Date: 10 October 2005

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Data are presented on a new type of microcavity that uses epitaxial overgrowth to localize self-organized quantum dots in a microcavity optical mode. The all-epitaxial design eliminates free surfaces from the active material, eliminates quantum dots from the mirror and passive cavity regions, and provides a mechanically robust design with high thermal conductivity. The epitaxial overgrowth leads to a new type of lens-shaped microcavity, while the mesa confinement leads to lithographically defined placement of the quantum dots near the center of the optical mode.
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42.55.Px Semiconductor lasers; laser diodes
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
73.21.La Quantum dots
73.63.Kv Quantum dots
78.67.Hc Quantum dots
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Bh Lenses, prisms and mirrors
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Field emission of individual carbon nanotube with in situ tip image and real work function

Zhi Xu, X. D. Bai, E. G. Wang, and Zhong L. Wang

Appl. Phys. Lett. 87, 163106 (2005); http://dx.doi.org/10.1063/1.2103420 (3 pages) | Cited 62 times

Online Publication Date: 10 October 2005

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The field emission properties of individual multiwalled carbon nanotubes have been measured simultaneously in correlation to the emitter images and their real work functions at tips by the in situ transmission electron microscopy method. The field emission of a single nanotube still follows the Fowler-Nordheim law. The field enhancement factor has been determined by the real work function rather than a given constant. In situ imaging and measurement show that the work function at the nanotube tip depends strongly on its structure and surface condition. This study provides an approach of direct linking field emission with the in situ emitter structure and the real work function at the emitter tip.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.46.-w Structure of nanoscale materials
68.37.Lp Transmission electron microscopy (TEM)

Indistinguishable single photons from a single-quantum dot in a two-dimensional photonic crystal cavity

S. Laurent, S. Varoutsis, L. Le Gratiet, A. Lemaître, I. Sagnes, F. Raineri, A. Levenson, I. Robert-Philip, and I. Abram

Appl. Phys. Lett. 87, 163107 (2005); http://dx.doi.org/10.1063/1.2103397 (3 pages) | Cited 40 times

Online Publication Date: 10 October 2005

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We report on the spontaneous emission of a single-quantum dot embedded in a two-dimensional photonic crystal cavity. The resonant coupling between the dot and the strongly localized optical mode significantly shortens the spontaneous emission lifetime, so that the coherence time of the emitted photons is dominated by radiative effects: The emitted photons are indistinguishable, with a mean wave-packet overlap as high as 72%.
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42.70.Qs Photonic bandgap materials
78.67.Hc Quantum dots

Highly oriented zinc blende CdSe nanoneedles

C. X. Shan, Z. Liu, and S. K. Hark

Appl. Phys. Lett. 87, 163108 (2005); http://dx.doi.org/10.1063/1.2105995 (3 pages) | Cited 7 times

Online Publication Date: 11 October 2005

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Epitaxial growth of highly oriented single-crystalline CdSe nanoneedles on GaAs substrates was obtained by metalorganic chemical vapor deposition using sputter-coated Au as a catalyst. Scanning electron microscopy revealed that they grew tidily along the ⟨110⟩ crystallographic directions and in parallel to the same directions of the substrate. Their density could be adjusted by applying different amounts of the catalyst. X-ray diffraction, transmission electron lattice imaging and electron diffraction showed that they have the zinc blende structure, which is rare for CdSe. Polarized photoluminescence studies on individual nanoneedles verify the zinc blende structure of the needles, and the strong near band edge emissions and no deep-level emissions reveal their good optical quality.
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81.05.Dz II-VI semiconductors
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors

Low-frequency noise spectroscopy in Au/n-GaAs Schottky diodes with InAs quantum dots

A. Tsormpatzoglou, N. A. Hastas, D. H. Tassis, C. A. Dimitriadis, G. Kamarinos, P. Frigeri, S. Franchi, E. Gombia, and R. Mosca

Appl. Phys. Lett. 87, 163109 (2005); http://dx.doi.org/10.1063/1.2106000 (3 pages) | Cited 3 times

Online Publication Date: 11 October 2005

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The temperature dependence of low-frequency noise in Au/n-GaAs Schottky diodes, with InAs quantum dots (QDs) embedded in the GaAs confining layers, is investigated in the temperature range of 77–298 K and at frequencies from 1 Hz to 5 kHz. Diodes prepared on samples with similar structure but without QDs exhibit 1/f behavior. In diodes containing QDs, in addition to the 1/f noise at low frequencies, generation-recombination (g-r) noise at higher frequencies was observed, related to single energy traps in the GaAs layer. Analysis of the experimental data has shown that the g-r noise is related to three traps with activation energies 0.234, 0.09 and 0.075 eV, corresponding to the ground and two excited confined states in the QDs.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices

Anomalous negative differential conductance in nanomechanical double barrier tunneling structures

Yutaka Majima, Yasuo Azuma, and Kouhei Nagano

Appl. Phys. Lett. 87, 163110 (2005); http://dx.doi.org/10.1063/1.2077863 (3 pages) | Cited 13 times

Online Publication Date: 12 October 2005

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Anomalous negative differential conductance (NDC) is observed along with a Coulomb staircase in the tunneling current-voltage curves of a nanomechanical double barrier tunneling structure consisting of a scanning vibrating probe/vacuum/colloidal Au nanodot/1,6-hexanedithiol/Au substrate. The peak voltages in the NDC phenomena when the sample voltage is applied correspond well with that of the probe voltage. We discuss a candidate mechanism of the NDC phenomena by taking into account the modulation of the tunneling rate between the scanning probe and an Au nanodot due to the nanometer-scale probe vibration.
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73.63.Bd Nanocrystalline materials
73.40.Gk Tunneling
73.40.Ns Metal-nonmetal contacts

Energy absorption of a nanoporous system subjected to dynamic loadings

Falgun B. Surani, Xinguo Kong, Deepam B. Panchal, and Yu Qiao

Appl. Phys. Lett. 87, 163111 (2005); http://dx.doi.org/10.1063/1.2106002 (3 pages) | Cited 33 times

Online Publication Date: 12 October 2005

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In a previous study [ X. Kong and Y. Qiao, Appl. Phys. Lett. 86, 151919 (2005) ], we analyzed the energy absorption behaviors of a nanoporous system subjected to quasi-static loadings. In this work, the performance of similar systems under dynamic loadings is investigated through a Hopkinson bar experiment. The energy absorption efficiency increases significantly with the loading rate, which is attributed to the effect of internal friction.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.46.-w Structure of nanoscale materials
61.43.Gt Powders, porous materials

Improved emission stability of single-walled carbon nanotube field emitters by plasma treatment

Won Seok Kim, Jeonghee Lee, Tae Won Jeong, Jung Na Heo, Byung Yoon Kong, Yong Wan Jin, J. M. Kim, Sung Hee Cho, Jong Hwan Park, and D. H. Choe

Appl. Phys. Lett. 87, 163112 (2005); http://dx.doi.org/10.1063/1.2099538 (3 pages) | Cited 19 times

Online Publication Date: 12 October 2005

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We investigated the effect of plasma treatment on single-walled carbon nanotube (SWCNT) field emitters, which were fabricated by printing a photoimageable SWCNT paste, to improve emission lifetime. The treatment was performed by applying a dc pulsed voltage between two electrodes, where the cathode was the SWCNT emitter to be treated and the anode was a bare indium-doped tin oxide glass, under inert gas (Xe/Ne) atmosphere. With increasing applied voltage and treatment time, the stability of the emission current at a constant electric field is improved, while the field to reach a required emission current becomes high. We attribute the improved emission stability to the removal of a small portion of protruding emitters, which dominate initial emission characteristics. The elimination of small number of prominent emitters allows a greater number of emitters to be active on emission with a compensation for higher electric-field application. We expect that the plasma treatment introduced in this letter will provide a quick and easy way to improve emission lifetime, which is essential for the commercialization of field emission display.
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79.70.+q Field emission, ionization, evaporation, and desorption
85.35.Kt Nanotube devices

Difference in formation of hydrogen and helium clusters in tungsten

K. O. E. Henriksson, K. Nordlund, A. Krasheninnikov, and J. Keinonen

Appl. Phys. Lett. 87, 163113 (2005); http://dx.doi.org/10.1063/1.2103390 (3 pages) | Cited 37 times

Online Publication Date: 12 October 2005

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The experimentally observed large difference in the depths of hydrogen and helium clusters formed in tungsten still lacks a fundamental explanation. Using density functional theory calculations, molecular dynamics simulations, and kinetic Monte Carlo calculations, we show that the fundamental mechanism behind the different clustering depths is significantly different behaviors of interstitial H and He atoms in W: H–H states are unstable for small interatomic distances whereas He–He states are strongly bound.
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61.72.J- Point defects and defect clusters

Nanoelectromechanical switches with vertically aligned carbon nanotubes

J. E. Jang, S. N. Cha, Y. Choi, Gehan A. J. Amaratunga, D. J. Kang, D. G. Hasko, J. E. Jung, and J. M. Kim

Appl. Phys. Lett. 87, 163114 (2005); http://dx.doi.org/10.1063/1.2077858 (3 pages) | Cited 58 times

Online Publication Date: 13 October 2005

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Electromechanical switching devices have been fabricated successfully employing vertically grown multiwalled carbon nanotubes (MWCNTs) from the prepatterned catalyst dots on the patterned device electrodes. The devices show various interesting switching characteristics depending on the length and the number of MWCNTs used. The device design not only simplifies the fabrication process, but also improves the integration density greatly. The device has a great potential in realizing technically viable nanoelectromechanical systems, such as switch, memory, fingers, or grippers.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.35.Kt Nanotube devices

Optical nonlinearity versus mechanical anharmonicity contrast in dynamic mode apertureless scanning near-field optical microscopy

Alpan Bek, Ralf Vogelgesang, and Klaus Kern

Appl. Phys. Lett. 87, 163115 (2005); http://dx.doi.org/10.1063/1.2108125 (3 pages) | Cited 12 times

Online Publication Date: 13 October 2005

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We show that the contrast mechanism in dynamic mode apertureless scanning near-field optical microscopy is in general a combination of both spatially nonlinear optical interaction and temporally anharmonic mechanical cantilever motion. Mechanical factors are found experimentally to easily overshadow the optical signal, leading to artifacts not yet well documented in the literature. Our algebraic analysis provides a systematic framework to identify and control the relative influence of the competing contrast origins.
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07.79.Fc Near-field scanning optical microscopes
42.65.-k Nonlinear optics

Self-aligned self assembly of multi-nanowire silicon field effect transistors

C. T. Black

Appl. Phys. Lett. 87, 163116 (2005); http://dx.doi.org/10.1063/1.2112191 (3 pages) | Cited 57 times

Online Publication Date: 13 October 2005

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We demonstrate the efficacy of diblock copolymer self assembly for solving key fabrication challenges of aggressively scaled silicon field effect transistors. These materials spontaneously form nanometer-scale patterns that self-align to larger-scale lithography, enabling construction of sub-lithographic semiconducting transistor channels composed of arrays of parallel nanowires with critical dimensions (15 nm width, 40 nm pitch) defined by self assembly. The number of nanowires in the arrays is readily adjusted, greatly reducing the complexity associated with width-scaling of nanowire transistors. We measured Schottky source/drain multi-nanowire n-channel devices comprised of 6, 8, 10, and 16 nanowires, with current drives of ∼ 5 μA/wire and current on/off ratios of ∼ 105.
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85.30.Tv Field effect devices
81.16.Dn Self-assembly
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Screening effects in InAs quantum-dot structures observed by photoluminescence and capacitance-voltage spectra

Stephan Lüttjohann, Cedrik Meier, Axel Lorke, Dirk Reuter, and Andreas D. Wieck

Appl. Phys. Lett. 87, 163117 (2005); http://dx.doi.org/10.1063/1.2112192 (3 pages) | Cited 2 times

Online Publication Date: 13 October 2005

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We have performed photoluminescence spectroscopy as well as capacitance-voltage spectroscopy on an ensemble of self-assembled InAs quantum dots that are embedded in a field-effect-transistor structure. By investigating the charging spectra as a function of excitation power density, we are able to demonstrate a buildup of a transient positive charge in the heterostructure that leads to a screening of the electric field inside the structure. Moreover, by taking photoluminescence and capacitance spectra simultaneously, we can correlate the charging state of the dots with the interband transitions of s- and p-shell. We find that the observation of photoluminescence from higher orbital states in such field-effect-transistor structures is not only a consequence of Pauli-blocking but also of the accumulation of holes inside the structure. Also, we are able to determine the energy shift between the higher-charged excitonic states X2− and X3− to be ΔE = 2.6 meV.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
73.21.La Quantum dots
73.63.Kv Quantum dots
71.35.Pq Charged excitons (trions)
85.30.Tv Field effect devices

Single-electron transistor mediated by C60 insertion inside a carbon nanotube

H. Y. Yu, D. S. Lee, S. H. Lee, S. S. Kim, S. W. Lee, Y. W. Park, U. Dettlaff-Weglikowskaand, and S. Roth

Appl. Phys. Lett. 87, 163118 (2005); http://dx.doi.org/10.1063/1.2112195 (3 pages) | Cited 9 times

Online Publication Date: 13 October 2005

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Electrical properties of C60 encapsulated peapod are investigated at various temperatures from room temperature down to T = 1.8 K. The current behavior induced by the applied gate and source-drain voltage shows that C60 peapods exhibit single-electron transistor properties. Gate-dependent conductance is enhanced at negative gate voltage and is suppressed and oscillate at positive gate voltage. This behavior is ascribed to the modulation of density of states by the insertion of C60s inside a carbon nanotube.
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85.35.Gv Single electron devices
85.35.Kt Nanotube devices
73.63.Fg Nanotubes

Synchrotron radiation x-ray photoelectron spectroscopy of Si nanocrystals grown onto Al2O3/Si surfaces

O. Renault, R. Marlier, M. Gely, B. De Salvo, T. Baron, M. Hansson, and N. T. Barrett

Appl. Phys. Lett. 87, 163119 (2005); http://dx.doi.org/10.1063/1.2105990 (3 pages) | Cited 6 times

Online Publication Date: 14 October 2005

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Synchrotron radiation x-ray photoelectron spectroscopy is used for the study of 5 nm Si nanocrystals (NCs) for applications in nonvolatile memory devices. A detailed peak shape analysis of the high-resolution Si 2p core-level spectra reveals average chemical shifts for the oxidized components consistent with those observed for planar oxidation. However, a much larger Gaussian width is found for each spectral component, reflecting the important level of structural disorder in the NCs, arising from stress produced during the kinetics of the oxide shell growth. Final state contributions to the core-level spectra are also discussed.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.46.-w Structure of nanoscale materials
73.20.-r Electron states at surfaces and interfaces

Insights into fluid tapping-mode atomic force microscopy provided by numerical simulations

Justin Legleiter and Tomasz Kowalewski

Appl. Phys. Lett. 87, 163120 (2005); http://dx.doi.org/10.1063/1.2105991 (3 pages) | Cited 17 times

Online Publication Date: 14 October 2005

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In an attempt to understand the physics underlying tapping mode atomic force microscopy (TMAFM) operated in fluids, simulations of complete TMAFM experiments were performed based on a cantilever model invoking the damped driven harmonic oscillator with a single degree of freedom with parameters based on real experiments, the most important of which was a low quality factor (Q). Such a low-Q oscillator captures some of the essential features related to operation of TMAFM in fluids, when compared to real experiments. Fluid TMAFM (a low-Q system) is characterized by a highly anharmonic deflection signal when compared to operation in air (a high-Q system). Our model was able to capture this hallmark of fluid TMAFM without the inclusion of more nuanced hydrodynamic effects. Such modeling can aid in the understanding of tip-sample interactions in fluid TMAFM and in the development of techniques to extract meaningful mechanical surface properties from such interactions.
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07.79.Lh Atomic force microscopes

Near-red emission from site-controlled pyramidal InGaN quantum dots

V. Pérez-Solórzano, A. Gröning, M. Jetter, T. Riemann, and J. Christen

Appl. Phys. Lett. 87, 163121 (2005); http://dx.doi.org/10.1063/1.2108126 (3 pages) | Cited 17 times

Online Publication Date: 14 October 2005

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We have fabricated InGaN nanostructures on top of GaN hexagonal pyramids by selective metalorganic vapor-phase epitaxy. With this approach, we are able to exactly control the position of the emitting quantum dot, which is an essential requirement for functionalized single-photon emitters. The emission properties as well as the relaxation and recombination mechanisms were investigated using spectroscopic methods. Regions of different confinement were identified, with the photoluminescence emission from the InGaN quantum dots around 2.03 eV and a decay time of 1.4 ns. The constant temperature behavior of the radiative decay time confirms its zero-dimensional character. Spatially resolved cathodoluminescence measurements attribute this emission to the apex of the pyramid.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.16.-c Methods of micro- and nanofabrication and processing

Direct measurement of the intrinsic RC roll-off in a radio frequency single electron transistor operated as a microwave mixer

D. J. Reilly and T. M. Buehler

Appl. Phys. Lett. 87, 163122 (2005); http://dx.doi.org/10.1063/1.2093929 (3 pages) | Cited 3 times

Online Publication Date: 14 October 2005

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By operating the radio frequency single electron transistor (rf-SET) as a mixer we present measurements in which the RC roll-off of the tunnel junctions is observed at high frequencies. Our technique makes use of the nonlinear rf-SET transconductance to mix high frequency gate signals and produce difference-frequency components that fall within the bandwidth of the rf-SET. At gate frequencies >15 GHz the induced charge on the rf-SET island is altered on time scales faster than the inverse tunnel rate, preventing mixer operation. We suggest the possibility of utilizing this technique to sense high frequency signals beyond the usual rf-SET bandwidth.
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85.35.Gv Single electron devices
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
73.23.Hk Coulomb blockade; single-electron tunneling
73.40.Gk Tunneling

Semiconductor gas sensor based on tin oxide nanorods prepared by plasma-enhanced chemical vapor deposition with postplasma treatment

Hui Huang, O. K. Tan, Y. C. Lee, T. D. Tran, M. S. Tse, and X. Yao

Appl. Phys. Lett. 87, 163123 (2005); http://dx.doi.org/10.1063/1.2106006 (3 pages) | Cited 36 times

Online Publication Date: 14 October 2005

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SnO2 thin films were deposited by radio-frequency inductively coupled plasma-enhanced chemical vapor deposition. Postplasma treatments were used to modify the microstructure of the as-deposited SnO2 thin films. Uniform nanorods with dimension of ∅7×100 nm were observed in the plasma-treated films. After plasma treatments, the optimal operating temperature of the plasma-treated SnO2 thin films decreased by 80 °C, while the gas sensitivity increased eightfold. The enhanced gas sensing properties of the plasma-treated SnO2 thin film were believed to result from the large surface-to-volume ratio of the nanorods’ tiny grain size in the scale comparable to the space-charge length and its unique microstructure of SnO2 nanorods rooted in SnO2 thin films.
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81.07.Bc Nanocrystalline materials
81.05.Hd Other semiconductors
82.80.-d Chemical analysis and related physical methods of analysis
81.16.-c Methods of micro- and nanofabrication and processing
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.-w Structure of nanoscale materials
68.55.A- Nucleation and growth

Controlled growth of well-faceted zigzag tin oxide mesostructures

Lisheng Huang, Lin Pu, Yi Shi, Rong Zhang, Benxi Gu, Youwei Du, and Stuart Wright

Appl. Phys. Lett. 87, 163124 (2005); http://dx.doi.org/10.1063/1.2112207 (3 pages) | Cited 16 times

Online Publication Date: 14 October 2005

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Reproducibly high-yield growth of zigzag fibers and well-faceted nanobelts of SnO2 was achieved via tuning the reactant vapor. The investigation of the morphological evolution via scanning electron microscopy and transmission electron microscopy hints that the formation of the zigzag SnO2 fiber is based on the pregrowing SnO2 nanobelt. The elucidation of the growth mechanism should provide a fully controlled route for reproducibly high-yield growth of zigzag fibers of SnO2 and give some valuable hints to synthesis other zigzag mesostructures. Optical characterizations of these structures show very weak defect-related emissions.
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81.10.Bk Growth from vapor
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
42.81.Bm Fabrication, cladding, and splicing
78.55.Hx Other solid inorganic materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
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