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21 Oct 2002

Volume 81, Issue 17, pp. 3119-3293

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Periodic array of intramolecular junctions of silicon nanowires

D. D. D. Ma, C. S. Lee, Y. Lifshitz, and S. T. Lee

Appl. Phys. Lett. 81, 3233 (2002); http://dx.doi.org/10.1063/1.1514399 (3 pages) | Cited 4 times

Online Publication Date: 15 October 2002

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The formation of periodic arrays of intramolecular junctions in silicon nanowires from a single growth process is reported. Scanning tunneling microscopic images show intramolecular junctions formed by fusing together two straight wire segments ( ∼ 3 nm in diameter) 5 and 10 nm long, respectively, at an angle of ∼ 30° with respect to each other. The junction repeats itself in a regular pattern along a nanowire, forming a striking superlattice ∼ 3 nm in diameter and at least several microns long. Scanning tunneling spectroscopic measurements reveal distinctly different current–voltage curves for the two different segments changing sharply across each junction. The segments are most probably formed by a periodic change of growth direction while the different electronic properties of the two segments forming the junction are attributed to the differences in surface structure and segment diameter. © 2002 American Institute of Physics.
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73.63.Nm Quantum wires
68.65.La Quantum wires (patterned in quantum wells)
81.07.Vb Quantum wires
68.65.Cd Superlattices
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Growth of self-assembled GaN quantum dots via the vapor–liquid–solid mechanism

C.-W. Hu, A. Bell, F. A. Ponce, D. J. Smith, and I. S. T. Tsong

Appl. Phys. Lett. 81, 3236 (2002); http://dx.doi.org/10.1063/1.1514394 (3 pages) | Cited 14 times

Online Publication Date: 15 October 2002

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Self-assembled nanometer-scale GaN quantum dots were fabricated on 6H–SiC(0001) substrates via the formation of Ga liquid droplets and their subsequent nitridation with a supersonic gas source seeded with NH3 molecules. The entire process was observed and controlled in situ and in real time in a low-energy electron microscope. The microstructure of the quantum dots was studied by high-resolution cross-sectional transmission electron microscopy illustrating the perfectly coherent wurtzite structure of GaN quantum dots with 5 nm base width. Spatially resolved cathodoluminescence spectra yield the characteristic band edge emission near 3.48 eV for larger size GaN dots. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
81.07.Ta Quantum dots
78.60.Hk Cathodoluminescence, ionoluminescence
81.16.Dn Self-assembly

Light emission from the shadows: Surface plasmon nano-optics at near and far fields

S. C. Hohng, Y. C. Yoon, D. S. Kim, V. Malyarchuk, R. Müller, Ch. Lienau, J. W. Park, K. H. Yoo, J. Kim, H. Y. Ryu, and Q. H. Park

Appl. Phys. Lett. 81, 3239 (2002); http://dx.doi.org/10.1063/1.1515134 (3 pages) | Cited 48 times

Online Publication Date: 15 October 2002

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When light illuminates a thick metal film perforated with small holes, shadows appear. At the nanoscopic level, however, light can be emitted predominantly from the metal surfaces between the holes—shadows can be indeed brighter than the lighted holes. The symmetry of the near-field emission pattern is determined by the symmetry of the surface plasmon waves. Surprisingly, these nanoscopic emission patterns from the metal can be preserved to the far-field region, where the pattern becomes sinusoidal. This unusual behavior of light emission from the shadows is explained by efficient wave vector selection. © 2002 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces
42.82.-m Integrated optics

Electroluminescence at 1.54 μm in Er-doped Si nanocluster-based devices

F. Iacona, D. Pacifici, A. Irrera, M. Miritello, G. Franzò, F. Priolo, D. Sanfilippo, G. Di Stefano, and P. G. Fallica

Appl. Phys. Lett. 81, 3242 (2002); http://dx.doi.org/10.1063/1.1516235 (3 pages) | Cited 84 times

Online Publication Date: 15 October 2002

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The electroluminescence (EL) properties of Er-doped Si nanoclusters (NC) embedded in metal–oxide–semiconductor devices are investigated. Due to the presence of Si NC dispersed in the SiO2 matrix, an efficient carrier injection occurs and Er is excited, producing an intense 1.54 μm room temperature EL. The EL properties as a function of the current density, temperature, and time have been studied in detail. We have also estimated the excitation cross section for Er under electrical pumping, finding a value of ∼ 1×10−14 cm2. This value is two orders of magnitude higher than the effective excitation cross section of Er ions through Si NC under optical pumping. In fact, quantum efficiencies of ∼1% are obtained at room temperature in these devices. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.60.Fi Electroluminescence

Focused-electron-beam-induced deposition of freestanding three-dimensional nanostructures of pure coalesced copper crystals

I. Utke, A. Luisier, P. Hoffmann, D. Laub, and P. A. Buffat

Appl. Phys. Lett. 81, 3245 (2002); http://dx.doi.org/10.1063/1.1517180 (3 pages) | Cited 52 times

Online Publication Date: 15 October 2002

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We report on direct writing of three-dimensional freestanding nanostructures of Cu by use of a focused electron beam (FEB) and the metalorganic precursor hfac-Cu-TMVS. Freestanding horizontal rods were deposited over about 10 μm length and consist of small 2–5 nm Cu nanocrystals dispersed in an amorphous matrix containing carbon, fluorine, silicon, and oxygen. The freestanding horizontal rods were used as support for further vertical deposits resulting in tips of coalesced facetted Cu nanocrystals of up to 100 nm in size. The almost constant deposition rate of 5–6 nm/s is in contrast to vertical tips on bulk supports, which show a deposition rate decreasing from 23 to 10 nm/s. The above results suggest a thermal decomposition process induced by electron energy absorption. © 2002 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.40.Sz Deposition technology
81.05.Bx Metals, semimetals, and alloys
61.46.-w Structure of nanoscale materials

Stress-induced growth of bismuth nanowires

Yang-Tse Cheng, Anita M. Weiner, Curtis A. Wong, Michael P. Balogh, and Michael J. Lukitsch

Appl. Phys. Lett. 81, 3248 (2002); http://dx.doi.org/10.1063/1.1515885 (3 pages) | Cited 26 times

Online Publication Date: 15 October 2002

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We report a method of making nanowires of bismuth (Bi) with diameters ranging from 30 to 200 nm and lengths up to several millimeters. The nanowires are extruded spontaneously at the rate of a few micrometers per second at room temperature from the surfaces of freshly grown composite thin films consisting of Bi and chrome–nitride. The high compressive stress in these composite thin films is the driving force responsible for the nanowire formation. This mechanism can also be used to create nanowires of other materials. © 2002 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.07.Vb Quantum wires
61.46.-w Structure of nanoscale materials
68.65.La Quantum wires (patterned in quantum wells)
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Filamentation and linewidth enhancement factor in InGaAs quantum dot lasers

P. M. Smowton, E. J. Pearce, H. C. Schneider, W. W. Chow, and M. Hopkinson

Appl. Phys. Lett. 81, 3251 (2002); http://dx.doi.org/10.1063/1.1516236 (3 pages) | Cited 29 times

Online Publication Date: 15 October 2002

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We report measurements of the near-field of broad-area lasers with quantum dot and quantum well active regions designed to emit at 1 μm. The quantum dot devices exhibit less filamentation than comparable quantum well devices, and exhibit a reduction in filamentation as the injection level is increased. This is consistent with a theory that includes the Coulomb coupling between dot and wetting-layer states on a microscopic level. The theory predicts a linewidth enhancement factor from −3 to 1, depending on carrier density and inhomogeneous broadening. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Self-organized strain engineering on GaAs (311)B: Template formation for quantum dot nucleation control

Q. Gong, R. Nötzel, G. J. Hamhuis, T. J. Eijkemans, and J. H. Wolter

Appl. Phys. Lett. 81, 3254 (2002); http://dx.doi.org/10.1063/1.1516637 (3 pages) | Cited 7 times

Online Publication Date: 15 October 2002

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A matrix of closely packed cells develops during molecular-beam epitaxy of In0.35Ga0.65As on GaAs (311)B, due to strain-driven growth instability. The established lateral strain distribution generates a unique template that controls the nucleation and growth of InAs quantum dots (QDs). The QDs exhibit pronounced improvement of the structural and optical properties with efficient carrier transfer from the template. Thus, self-organization of a two-dimensionally connected quantum dot network is demonstrated. © 2002 American Institute of Physics.
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81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.16.Dn Self-assembly
68.65.Hb Quantum dots (patterned in quantum wells)
81.05.Ea III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Impedance analysis of a radio-frequency single-electron transistor

H. D. Cheong, T. Fujisawa, T. Hayashi, Y. Hirayama, and Y. H. Jeong

Appl. Phys. Lett. 81, 3257 (2002); http://dx.doi.org/10.1063/1.1515883 (3 pages) | Cited 14 times

Online Publication Date: 15 October 2002

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We investigate rf transport through an AlGaAs/GaAs single-electron transistor (SET). The presented rf–SET scheme provides a transmission coefficient proportional to the admittance of the device, which is desirable for impedance analysis as well as for high-sensitivity charge detection. The impedance of a SET, including the small tunneling capacitance, is successfully analyzed at the high frequency of 643 MHz, and is compared with a simple model. The ability to measure the impedance of a SET would expand the measurable regime of single-electron tunneling behavior. © 2002 American Institute of Physics.
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85.35.Gv Single electron devices
85.30.De Semiconductor-device characterization, design, and modeling
84.40.Dc Microwave circuits
73.23.Hk Coulomb blockade; single-electron tunneling
73.40.Gk Tunneling

Carbon nanotube memory devices of high charge storage stability

J. B. Cui, R. Sordan, M. Burghard, and K. Kern

Appl. Phys. Lett. 81, 3260 (2002); http://dx.doi.org/10.1063/1.1516633 (3 pages) | Cited 78 times

Online Publication Date: 15 October 2002

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Molecular memory devices with semiconducting single-walled carbon nanotubes constituting a channel of 150 nm in length are described. Data storage is achieved by sweeping gate voltages in the range of 3 V, associated with a storage stability of more than 12 days at room temperature. By annealing in air or controlled oxygen plasma exposure, efficient switching devices could be obtained from thin nanotube bundles that originally showed only a small gate dependence of conductance. © 2002 American Institute of Physics.
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85.35.Kt Nanotube devices
73.63.Fg Nanotubes
81.07.Nb Molecular nanostructures

Nanopatterning of Si/SiGe electrical devices by atomic force microscopy oxidation

Xiang-Zheng Bo, Leonid P. Rokhinson, Haizhou Yin, D. C. Tsui, and J. C. Sturm

Appl. Phys. Lett. 81, 3263 (2002); http://dx.doi.org/10.1063/1.1515113 (3 pages) | Cited 12 times

Online Publication Date: 15 October 2002

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Two nanopatterning methods for silicon/silicon-germanium (Si/SiGe) heterostructures are demonstrated: (1) direct atomic force microscopy (AFM) oxidation on SiGe layers and (2) AFM oxidation on silicon followed by selective wet etching of SiGe. When directly oxidizing SiGe alloys, minimum linewidths of 20 nm were achieved by adjusting the bias voltage of the AFM tip. By AFM oxidation and selective wet etching, a 10-nm-thick conducting SiGe layer was patterned to form features under ∼50 nm. Fabricated SiGe quantum dots with side gates exhibited Coulomb blockade oscillation. © 2002 American Institute of Physics.
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81.16.Pr Micro- and nano-oxidation
81.16.Ta Atom manipulation
81.65.Cf Surface cleaning, etching, patterning
81.65.Mq Oxidation
73.23.Hk Coulomb blockade; single-electron tunneling
81.05.Cy Elemental semiconductors
81.05.Hd Other semiconductors
85.35.Ds Quantum interference devices
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