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15 Jul 2002

Volume 81, Issue 3, pp. 391-566

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Electrical conductivity and thermopower of Cu–SiO2 nanogranular films

W. Chen, J. J. Lin, X. X. Zhang, H. K. Shin, J. S. Dyck, and C. Uher

Appl. Phys. Lett. 81, 523 (2002); http://dx.doi.org/10.1063/1.1493668 (3 pages) | Cited 4 times

Online Publication Date: 2 July 2002

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We have measured the thermopower S and electrical conductivity σ in a series of Cux(SiO2)1−x nanogranular films between 2 and 300 K with Cu volume fraction x varying from 0.43 up to 1.0. At low temperatures, disorder-enhanced electron–electron interaction effects dictate the behavior of σ. A crossover of the temperature dependence from σ∝math to σ∝T1/3 is observed as x is lowered and the metal–insulator transition is approached. S is small, shows linear temperature dependence, and is rather insensitive to the change of x. Effects of annealing are also discussed. © 2002 American Institute of Physics.
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73.61.-r Electrical properties of specific thin films
73.50.Lw Thermoelectric effects
72.60.+g Mixed conductivity and conductivity transitions
61.72.Cc Kinetics of defect formation and annealing
72.15.Jf Thermoelectric and thermomagnetic effects
72.20.Pa Thermoelectric and thermomagnetic effects
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Carbon nanofibers synthesized by decomposition of alcohol at atmospheric pressure

N. Jiang, R. Koie, T. Inaoka, Y. Shintani, K. Nishimura, and A. Hiraki

Appl. Phys. Lett. 81, 526 (2002); http://dx.doi.org/10.1063/1.1494102 (3 pages) | Cited 13 times

Online Publication Date: 2 July 2002

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In the present study, we fabricated the carbon nanofibers (CNFs) by decomposition of methyl alcohol at atmospheric pressure. The CNFs were grown on Ni/Si substrates using simplified hot-filament chemical vapor deposition equipment. The deposits mainly consist of the semicrystalline CNFs, in which a few of carbon nanotubes are included. On the 30-nm-thick Ni/Si substrates, the mean length of the CNFs is 2–3 μm, and their average diameter is less than 100 nm. The as-deposited CNFs were evaluated by both scanning and transmission electron microscopes. The field-electron-emission properties of CNFs were characterized as well. © 2002 American Institute of Physics.
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81.16.Be Chemical synthesis methods
81.07.De Nanotubes
81.05.U- Carbon/carbon-based materials
61.46.-w Structure of nanoscale materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.37.Lp Transmission electron microscopy (TEM)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
79.70.+q Field emission, ionization, evaporation, and desorption

Two-dimensional array of self-assembled AlInAs quantum wires

S. Francoeur, A. G. Norman, A. Mascarenhas, E. D. Jones, J. L. Reno, S. R. Lee, and D. M. Follstaedt

Appl. Phys. Lett. 81, 529 (2002); http://dx.doi.org/10.1063/1.1493222 (3 pages) | Cited 4 times

Online Publication Date: 2 July 2002

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We present the optical and structural characterization of a two-dimensional array of self-organized AlInAs quantum wires. The structure was created by epitaxially stacking along the [001] direction thin self-assembled, [100]-oriented, superlattices separated by homogeneous layers of Al0.48In0.52As. Vertical and lateral self-alignment results in a highly regular array of wires oriented along the [010] direction. The wire cross-sectional dimensions are about 10×14.4 nm2 and their density is 1.9×1011 cm−2. The energy and the nature of the electronic transitions are significantly affected by confinement in two dimensions: (1) a blueshift of about 100 meV is observed and (2) the two lowest energy transitions are both polarized along the [010] direction. For comparison, the two lowest energy transitions of a lateral superlattice with similar characteristics have a heavy- (polarization along [010]) and a light-hole character (polarization along [100]). Large polarization ratios are measured for both transitions. © 2002 American Institute of Physics.
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68.65.La Quantum wires (patterned in quantum wells)
78.67.Lt Quantum wires

Single-electron transistor as a radio-frequency mixer

R. Knobel, C. S. Yung, and A. N. Cleland

Appl. Phys. Lett. 81, 532 (2002); http://dx.doi.org/10.1063/1.1493221 (3 pages) | Cited 25 times

Online Publication Date: 2 July 2002

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We demonstrate the use of the single-electron transistor as a radio-frequency mixer, based on the nonlinear dependence of current on gate charge. This mixer can be used for high-frequency, ultrasensitive charge measurements over a broad and tunable range of frequencies. We demonstrate operation of the mixer, using a lithographically defined thin-film aluminum transistor, in both the superconducting and normal states of aluminum, over frequencies from 10 to 300 MHz. We have operated the device both as a homodyne detector and as a phase-sensitive heterodyne mixer. We demonstrate a charge sensitivity of <4×10−3 e/math, limited by room-temperature electronics. An optimized mixer has a theoretical charge sensitivity of ≲1.5×10−5 e/math. © 2002 American Institute of Physics.
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85.35.Gv Single electron devices
85.25.Cp Josephson devices
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.40.-x Radiowave and microwave (including millimeter wave) technology
73.61.At Metal and metallic alloys
74.78.-w Superconducting films and low-dimensional structures
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
07.68.+m Photography, photographic instruments; xerography
06.30.-k Measurements common to several branches of physics and astronomy

Optical properties of Mn-doped CdS nanocrystals fabricated by sequential ion implantation

Yoshihiko Kanemitsu, Hiroki Matsubara, and C. W. White

Appl. Phys. Lett. 81, 535 (2002); http://dx.doi.org/10.1063/1.1494468 (3 pages) | Cited 32 times

Online Publication Date: 2 July 2002

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We have studied luminescence spectrum and dynamics of Mn-doped CdS nanocrystals fabricated by sequential Cd+, S+, and Mn+ ion implantation into Al2O3 matrices. The photoluminescence (PL) due to the Mn2+ intra-3d transition is clearly observed near 570 nm in Mn-doped CdS nanocrystals. The PL excitation spectrum of the Mn2+ luminescence in Mn-doped CdS nanocrystals is similar to the optical absorption spectrum and PL excitation spectrum of undoped CdS nanocrystals. Our spectroscopic data show that ion-beam synthesis is one of the methods of the fabrication of doped semiconductor nanocrystals. The luminescence mechanism of Mn-doped CdS nanocrystals will be discussed. © 2002 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects

Resonant tunneling of Si nanocrystals embedded in Al2O3 matrix synthesized by vacuum electron-beam co-evaporation

Q. Wan, T. H. Wang, M. Zhu, and C. L. Lin

Appl. Phys. Lett. 81, 538 (2002); http://dx.doi.org/10.1063/1.1491298 (3 pages) | Cited 15 times

Online Publication Date: 2 July 2002

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High vacuum electron-beam co-evaporation, followed by N2 annealing at 500 °C is used for preparing of silicon nanocrystals (Si NCs) embedded in Al2O3 dielectric matrix. X-ray diffraction and transmission electron microscopy are used to investigate the structures of Si+Al2O3 films and estimate the mean diameter of the Si NCs. The electrical properties of the diode containing Si NCs embedded in Al2O3 are studied at room temperature and resonant tunneling effect with large voltage gap is observed. A circuit model based on resonant tunneling is proposed to simulate the measured I–V curve. © 2002 American Institute of Physics.
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73.63.Kv Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
73.23.-b Electronic transport in mesoscopic systems
73.61.Cw Elemental semiconductors
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.72.Cc Kinetics of defect formation and annealing

Electrical behavior of isolated multiwall carbon nanotubes characterized by scanning surface potential microscopy

S. B. Schujman, R. Vajtai, S. Biswas, B. Dewhirst, L. J. Schowalter, and P. Ajayan

Appl. Phys. Lett. 81, 541 (2002); http://dx.doi.org/10.1063/1.1490401 (3 pages) | Cited 7 times

Online Publication Date: 2 July 2002

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We measured the surface electric potential distribution on individual, electrically contacted and biased, multiwall carbon nanotubes using scanning surface potential microscopy. The voltage varies linearly along the nanotube and the voltage drop is directly proportional to the bias applied between electrodes. Its resistance decreases four times when a 4.5 V bias is applied between the nanotube and the substrate. Under these conditions, we were able to resolve the voltage drop along the nanotube and at the contacts, providing a unique way of measuring contact resistance, which is observed in this case to be on the order of 50 kΩ. © 2002 American Institute of Physics.
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73.63.Fg Nanotubes
73.40.Cg Contact resistance, contact potential
68.37.Ps Atomic force microscopy (AFM)
85.35.Kt Nanotube devices

Observation of Coulomb staircases of both tunneling current and displacement current in nanomechanical double barrier tunneling structures

Kouhei Nagano, Atsushi Okuda, and Yutaka Majima

Appl. Phys. Lett. 81, 544 (2002); http://dx.doi.org/10.1063/1.1493228 (3 pages) | Cited 18 times

Online Publication Date: 2 July 2002

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Displacement current staircase due to Coulomb blockade is observed together with a tunneling current staircase in nanomechanical double barrier tunneling structures that consist of scanning vibrating probe/colloidal Au particles/vacuum/PtPd substrate. We discuss the motion of single electrons on and through the Au particles from both the tunneling and displacement current staircases, and demonstrate the electron shuttle phenomenon due to nanomechanical probe vibration. © 2002 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Ds Quantum interference devices
85.35.Gv Single electron devices
73.40.Gk Tunneling
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.79.-v Scanning probe microscopes and components
81.05.Bx Metals, semimetals, and alloys
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