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18 Feb 2002

Volume 80, Issue 7, pp. 1111-1310

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Single-electron tunneling at room temperature in cobalt nanoparticles

H. Graf, J. Vancea, and H. Hoffmann

Appl. Phys. Lett. 80, 1264 (2002); http://dx.doi.org/10.1063/1.1450251 (3 pages) | Cited 25 times

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We report on the observation of the Coulomb blockade with Coulomb staircases at room temperature in cobalt nanoparticles, with sizes ranging between 1 and 4 nm. A monolayer of these particles is supported by a thin 1–2 nm thick Al2O3 film, deposited on a smooth Au(111) surface. The local electrical transport on isolated Co clusters was investigated with a scanning tunneling microscope (STM). The tunnel contact of the STM tip allowed us to observe single-electron tunneling in the double barrier system STM-tip/Co/Al2O3/Au. Very high values of the Coulomb blockade of up to 1.0 V were reproducibly measured at room temperature on different particles with this setup. The current–voltage characteristics fit well by simulations based on the orthodox theory of single-electron tunneling. © 2002 American Institute of Physics.
Show PACS
73.23.Hk Coulomb blockade; single-electron tunneling
75.50.Tt Fine-particle systems; nanocrystalline materials
75.45.+j Macroscopic quantum phenomena in magnetic systems
73.63.Bd Nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys

Structural characterization of cup-stacked-type nanofibers with an entirely hollow core

M. Endo, Y. A. Kim, T. Hayashi, Y. Fukai, K. Oshida, M. Terrones, T. Yanagisawa, S. Higaki, and M. S. Dresselhaus

Appl. Phys. Lett. 80, 1267 (2002); http://dx.doi.org/10.1063/1.1450264 (3 pages) | Cited 121 times

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Straight long carbon nanofibers with a large hollow core obtained by a floating reactant method show a stacking morphology of truncated conical graphene layers, which in turn exhibit a large portion of open edges on the outer surface and also in the inner channels. Through a judicious choice of oxidation conditions, nanofibers with increased active edge sites are obtained without disrupting the fiber’s morphology. A graphitization process induces a morphological change from a tubular type to a reversing saw-toothed type and the formation of loops along the inner channel of the nanofibers, accompanied by a decrease in interlayer spacing. © 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.De Nanotubes

Efficient quantum well to quantum dot tunneling: Analytical solutions

S. L. Chuang and N. Holonyak

Appl. Phys. Lett. 80, 1270 (2002); http://dx.doi.org/10.1063/1.1449535 (3 pages) | Cited 31 times

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Tunneling transfer of carriers from a quantum well (collector) into a quantum dot is investigated theoretically using the transition-probability approach of Bardeen. The approach is attractive since it allows analysis of the tunneling rate using the wave function of the initial state in the quantum well and that of the final state in the quantum dot. We derive an analytical tunneling formula for the transition rate. We show that the quantum well to quantum dot tunneling can be extremely fast when the well, barrier, and dot potentials are properly designed. These calculations show that, in the recent experiment of a quantum-dot laser using an auxiliary InGaP quantum well for carrier collection and lateral transport followed by tunneling to the quantum dot layer via a thin coupling barrier, the added requirement of tunneling does not impede the population of the dot states. © 2002 American Institute of Physics.
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73.63.Hs Quantum wells
73.63.Kv Quantum dots
03.65.Xp Tunneling, traversal time, quantum Zeno dynamics
73.40.Gk Tunneling
73.21.Fg Quantum wells
73.21.La Quantum dots

Self-organized lateral ordering for vertically aligned PbSe/PbEuTe quantum-dot superlattices

A. Raab, R. T. Lechner, and G. Springholz

Appl. Phys. Lett. 80, 1273 (2002); http://dx.doi.org/10.1063/1.1447319 (3 pages) | Cited 7 times

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The growth of vertically aligned self-assembled PbSe/Pb1−xEuxTe quantum-dot superlattices is found to result in a pronounced hexagonal lateral ordering tendency accompanied by a narrowing of the size distribution. In addition, the lateral dot separations and dot densities become tunable by changes in the spacer thickness with an almost twofold density increase for spacer thicknesses increasing from 100 to 275Å. Similar marked changes are also found for PbSe dot sizes and shapes. This could provide additional means for the tuning of the optical and electronic properties of the dots. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.16.Dn Self-assembly
68.65.Cd Superlattices

Spring constant and damping constant tuning of nanomechanical resonators using a single-electron transistor

K. Schwab

Appl. Phys. Lett. 80, 1276 (2002); http://dx.doi.org/10.1063/1.1449533 (3 pages) | Cited 32 times

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By fabricating a single-electron transistor onto a mechanical system in a high magnetic field, it is shown that one can manipulate both the mechanical spring constant and damping constant by adjusting a potential of a nearby gate electrode. The spring constant effect is shown to be usable to control the resonant frequency of silicon-based nanomechanical resonators, while an additional damping constant effect is relevant for the resonators built upon carbon nanotube or similar molecular-sized materials. This could prove to be a very convenient scheme to actively control the response of nanomechanical systems for a variety of applications including radio-frequency signal processing, ultrasensitive force detection, and fundamental physics explorations. © 2002 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.35.Gv Single electron devices

Photoluminescence of ultrasmall Ge quantum dots grown by molecular-beam epitaxy at low temperatures

M. W. Dashiell, U. Denker, C. Müller, G. Costantini, C. Manzano, K. Kern, and O. G. Schmidt

Appl. Phys. Lett. 80, 1279 (2002); http://dx.doi.org/10.1063/1.1430508 (3 pages) | Cited 53 times

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Low-temperature epitaxial growth of Si–Ge heterostructures opens possibilities for synthesizing very small and abrupt low-dimensional structures due to the low adatom surface mobilities. We present photoluminescence from Ge quantum structures grown by molecular-beam epitaxy at low temperatures which reveals a transition from two-dimensional to three-dimensional growth. Phononless radiative recombination is observed from 〈105〉 faceted Ge quantum dots with height of approximately 0.9 nm and lateral width of 9 nm. Postgrowth annealing reveals a systematic blueshift of the Ge quantum dot’s luminescence and a reduction in nonradiative recombination channels. With increasing annealing temperatures Si–Ge intermixing smears out the three-dimensional carrier localization around the dot. © 2002 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Ap Elemental semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
68.65.Hb Quantum dots (patterned in quantum wells)
73.21.La Quantum dots
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions
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