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NANOSCALE SCIENCE AND DESIGN

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Adiabatic switching in coupled quantum dot systems facilitated by the coexistence of “molecular” and “atomic” states

R. Akis, D. Vasileska, and D. K. Ferry

Appl. Phys. Lett. 80, 4440 (2002); http://dx.doi.org/10.1063/1.1485102 (3 pages)

Online Publication Date: 31 May 2002

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We model a double quantum dot system defined by a split metal gate over a GaAs/AlGaAs heterostructure, with the dots being coupled via a quantum point contact. Hybridization effects analogous to that of molecules are apparent. However, contrary to some previous studies, we find that there can be a coexistence of “atomic” and “molecular” regimes. The resulting behavior may be utilized to create a device that switches adiabatically, providing a possible route to dissipation-free computing. © 2002 American Institute of Physics.

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73.21.La	Quantum dots
73.63.Kv	Quantum dots
85.35.Be	Quantum well devices (quantum dots, quantum wires, etc.)
03.67.Lx	Quantum computation architectures and implementations

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Laser-focused nanofabrication: Beating of two atomic resonances

E. Jurdik, J. Hohlfeld, H. van Kempen, Th. Rasing, and J. J. McClelland

Appl. Phys. Lett. 80, 4443 (2002); http://dx.doi.org/10.1063/1.1485104 (3 pages) | Cited 9 times

Online Publication Date: 31 May 2002

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We deposit a laser-collimated chromium beam onto a substrate through a laser standing-wave (SW) tuned above the atomic resonance at either of the two ⁵²Cr transitions ⁷S₃→⁷P3o at 427.600 nm or ⁷S₃→⁷P4o at 425.553 nm. In both of these cases, the resulting pattern on the surface consists of nanolines with a period of that of the SW. We extend the range of periods accessible to laser-focused atom deposition by superimposing the structures grown at both these resonances. The resulting beating pattern exhibits a period of 44.46±0.04 μm as determined with a polarizing optical microscope. This structure provides a link between nanoscopic and macroscopic worlds and could potentially become a calibration standard for length metrology. © 2002 American Institute of Physics.

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81.16.Mk	Laser-assisted deposition
81.15.Fg	Pulsed laser ablation deposition
85.40.Sz	Deposition technology
81.16.Ta	Atom manipulation
37.10.Vz	Mechanical effects of light on atoms, molecules, and ions

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Electrical cutting and nicking of carbon nanotubes using an atomic force microscope

Ji-Yong Park, Yuval Yaish, Markus Brink, Sami Rosenblatt, and Paul L. McEuen

Appl. Phys. Lett. 80, 4446 (2002); http://dx.doi.org/10.1063/1.1485126 (3 pages) | Cited 39 times

Online Publication Date: 31 May 2002

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An atomic force microscope (AFM) has been used to modify the electrical properties of carbon nanotube devices. By applying voltage pulses from a metal-coated AFM tip, electrical breaks (“cuts”) or tunneling barriers (“nicks”) can be created at any point along a tube. These methods are applied to make single tube devices by cutting uninteresting nanotubes or create small quantum dots with large charging energies by placing two tunneling barriers 50 nm apart along a nanotube. © 2002 American Institute of Physics.

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81.07.De	Nanotubes
81.07.Ta	Quantum dots
68.65.Hb	Quantum dots (patterned in quantum wells)
85.35.Kt	Nanotube devices
61.46.-w	Structure of nanoscale materials
68.37.Ps	Atomic force microscopy (AFM)
85.35.Be	Quantum well devices (quantum dots, quantum wires, etc.)

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Erbium doped nanostructured tin–silicate glass–ceramic composites

N. Chiodini, A. Paleari, G. Brambilla, and E. R. Taylor

Appl. Phys. Lett. 80, 4449 (2002); http://dx.doi.org/10.1063/1.1485105 (3 pages) | Cited 22 times

Online Publication Date: 31 May 2002

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Er-doped tin–silicate glass–ceramic composites were synthesized from Si, Er and Sn molecular precursors by following a sol–gel method. Optical spectroscopy and electron microscopy showed that the resulting material is composed of an amorphous silica network that encloses submicrometric SnO₂ crystalline clusters. Analysis of the luminescence properties shows that Er ions are, at least partially, trapped in the crystalline phase. Raman spectra show that nanostructured tin–silicate composites act as low phonon energy hosts for rare earth ions and are thus suitable for photonic applications. © 2002 American Institute of Physics.

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81.05.Pj	Glass-based composites, vitroceramics
61.46.-w	Structure of nanoscale materials
81.07.Bc	Nanocrystalline materials
81.10.Dn	Growth from solutions
81.10.Fq	Growth from melts; zone melting and refining
81.15.Lm	Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
63.22.-m	Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.35.+c	Brillouin and Rayleigh scattering; other light scattering
78.55.Hx	Other solid inorganic materials

DEVICE PHYSICS

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Fermi level unpinning in ex situ Schottky contacts on n-GaAs capped with low-temperature-grown GaAs

Saurabh Lodha, David B. Janes, and Nien-Po Chen

Appl. Phys. Lett. 80, 4452 (2002); http://dx.doi.org/10.1063/1.1484243 (3 pages) | Cited 9 times

Online Publication Date: 31 May 2002

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The Schottky barrier behavior of a GaAs layer structure consisting of a thick n-GaAs layer, capped by a thin (3.5 nm) layer of as-grown unintentionally or Be-doped low-temperature-grown GaAs (LTG:GaAs), both grown by molecular beam epitaxy, has been studied. Nonalloyed, ex situ Schottky contacts using three different metals were fabricated on the LTG:GaAs-capped layers and on n-GaAs control samples, in order to study the interface barrier height (ϕ_b) versus the metal work function (ϕ_m). High frequency capacitance–voltage measurements, along with simulations that incorporate a complete description of the defect states in LTG:GaAs, were used to extract the ϕ_b values. The variation in ϕ_b with the metal work function is nearly six times greater in the LTG:GaAs capped contacts than in uncapped n-GaAs samples. This direct observation of Fermi level unpinning is consistent with earlier measurements that indicated the inhibited oxidation of LTG:GaAs layers in comparable structures for short air exposure times. © 2002 American Institute of Physics.

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73.40.Ns	Metal-nonmetal contacts
73.30.+y	Surface double layers, Schottky barriers, and work functions
71.55.Eq	III-V semiconductors

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Space degradation of multijunction solar cells: An electroluminescence study

M. Zazoui and J. C. Bourgoin

Appl. Phys. Lett. 80, 4455 (2002); http://dx.doi.org/10.1063/1.1485134 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2002

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We propose the use of electroluminescence to measure irradiation-induced degradation of multijunction photovoltaic cells in order to probe the degradation of each individual junction. We illustrate the technique by studying the decrease of the luminescence of GaInP, GaAs and Ge junctions of a triple-junction solar cell produced by 1 MeV electrons for fluences corresponding to space conditions. © 2002 American Institute of Physics.

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84.60.Jt	Photoelectric conversion
85.30.De	Semiconductor-device characterization, design, and modeling
61.82.Fk	Semiconductors
07.89.+b	Environmental effects on instruments (e.g., radiation and pollution effects)
78.60.Fi	Electroluminescence
61.80.Fe	Electron and positron radiation effects

INTERDISCIPLINARY AND GENERAL PHYSICS

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Use of near-surface channel conductance and differential capacitance versus potential measurements to correlate inversion layer formation with low effective surface recombination velocities at n-Si/liquid contacts

David J. Michalak and Nathan S. Lewis

Appl. Phys. Lett. 80, 4458 (2002); http://dx.doi.org/10.1063/1.1479456 (3 pages) | Cited 7 times

Online Publication Date: 31 May 2002

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Near-surface channel conductance measurements, differential capacitance versus potential measurements, and surface recombination velocity measurements have been performed on (111)- and (100)-oriented n-type Si samples in contact with nitrogen and/or liquid electrolyte solutions containing I₂, I₂/I⁻, ferrocene^+/0, or decamethylferrocene^+/0 in either methanol or tetrahydrofuran. Si/liquid contacts that displayed a low effective surface recombination velocity S corresponded to those that formed an inversion layer at the solid/liquid contact as indicated by channel conductance measurements or by differential capacitance versus potential measurements. Contacts that did not produce an inversion layer at the Si surface did not produce low effective S values. The observed behavior is consistent with the known energetics of Si/liquid contacts and provides an explanation for the low effective S values observed in these systems. © 2002 American Institute of Physics.

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73.40.Mr	Semiconductor-electrolyte contacts
72.20.Jv	Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr	Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.25.+i	Surface conductivity and carrier phenomena

ERRATA

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Erratum: “Microwave surface resistance of MgB₂” [Appl. Phys. Lett. 80, 2347 (2002)]

A. A. Zhukov, A. Purnell, Y. Miyoshi, Y. Bugoslavsky, Z. Lockman, A. Berenov, H. Y. Zhai, H. M. Christen, M. P. Paranthaman, D. H. Lowndes, M. H. Jo, M. G. Blamire, Ling Hao, J. Gallop, J. L. MacManus-Driscoll, et al.

Appl. Phys. Lett. 80, 4461 (2002); http://dx.doi.org/10.1063/1.1482422 (1 page) | Cited 4 times

Online Publication Date: 31 May 2002

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Abstract Unavailable

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74.72.-h	Cuprate superconductors
74.25.N-	Response to electromagnetic fields
74.78.-w	Superconducting films and low-dimensional structures
99.10.Cd	Errata

SECTION LISTING

BROWSE VOLUMES

10 Jun 2002

Volume 80, Issue 23, pp. 4291-4461

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