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28 Jan 2002

Volume 80, Issue 4, pp. 535-701

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Surface-emitting spin-polarized In0.4Ga0.6As/GaAs quantum-dot light-emitting diode

S. Ghosh and P. Bhattacharya

Appl. Phys. Lett. 80, 658 (2002); http://dx.doi.org/10.1063/1.1436526 (3 pages) | Cited 13 times

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We report the properties of a spin-polarized In0.4Ga0.6As/GaAs quantum-dot surface-light-emitting diode with a Ga0.974Mn0.026As spin injector layer. Spin-polarized holes from this ferromagnetic layer recombine with electrons in the quantum dots to produce circularly polarized light output. The peak optical polarization efficiency at 5.1 K is 18% and the spin injection efficiency is estimated to be ∼36%. The temperature dependence of spin injection is almost identical to the temperature dependence of magnetization in the (Ga, Mn)As layer. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.67.Hc Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Size-controlled highly luminescent silicon nanocrystals: A SiO/SiO2 superlattice approach

M. Zacharias, J. Heitmann, R. Scholz, U. Kahler, M. Schmidt, and J. Bläsing

Appl. Phys. Lett. 80, 661 (2002); http://dx.doi.org/10.1063/1.1433906 (3 pages) | Cited 287 times

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Phase separation and thermal crystallization of SiO/SiO2 superlattices results in ordered arranged silicon nanocrystals. The preparation method which is fully compatible with Si technologies enables independent control of particle size as well as of particle density and spatial position by using a constant stoichiometry of the layers. Transmission electron microscopy investigations confirm the size control in samples with an upper limit of the nanocrystal sizes of 3.8, 2.5, and 2.0 nm without decreasing the silicon nanocrystal density for smaller sizes. The nanocrystals show a strong luminescence intensity in the visible and near-infrared region. A size-dependent blueshift of the luminescence and a luminescence intensity comparable to porous Si are observed. Nearly size independent luminescence intensity without bleaching effects gives an indirect proof of the accomplishment of the independent control of crystal size and number. © 2002 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
64.75.-g Phase equilibria
68.37.Lp Transmission electron microscopy (TEM)
68.65.Cd Superlattices

Characterization of a two-dimensional cantilever array with through-wafer electrical interconnects

Eugene M. Chow, Goksen G. Yaralioglu, Calvin F. Quate, and Thomas W. Kenny

Appl. Phys. Lett. 80, 664 (2002); http://dx.doi.org/10.1063/1.1435804 (3 pages) | Cited 11 times

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The characterization of two-dimensional micromachined silicon cantilever arrays with integrated through-wafer electrical interconnects is presented. The approach addresses alignment and density issues associated with operating two-dimensional scanning probe arrays. The tungsten based interconnect (30 μm diameter, 1 Ω resistance) is shown not to degrade the sensitivity of the piezoresistive deflection sensor embedded on each cantilever. Operation of the array (up to 2×7) as a microscope for imaging large areas (3.8×0.45 mm2) and with vertical row stitching is demonstrated with images of samples orders of magnitude larger than images possible with standard atomic force microscope techniques. © 2002 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Single-electron tunneling effects in a metallic double dot device

T. Junno, S. -B. Carlsson, H. Q. Xu, L. Samuelson, A. O. Orlov, and G. L. Snider

Appl. Phys. Lett. 80, 667 (2002); http://dx.doi.org/10.1063/1.1436532 (3 pages) | Cited 6 times

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We report on differential conductance measurements on a gold double-dot structure at 4.2 K. The two dots were connected in series by tunnel junctions formed by atomic force microscopy manipulation of nanodisks. The tunnel junctions were made strongly asymmetric. The characteristic honeycomb-shaped charging diagram separating different Coulomb blockade regions of well-defined occupancy of electrons was observed and the cells in the charging diagram were found to be skewed by the asymmetry of the tunnel junctions. In addition, a double-dot Coulomb staircase structure, with steps of varying width, was observed and was studied for varying gate voltage. The occupancy of electrons on the two dots was determined as a function of both drain source and gate voltages. © 2002 American Institute of Physics.
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85.35.Gv Single electron devices
85.35.Ds Quantum interference devices
73.63.Kv Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.La Quantum dots
73.23.Hk Coulomb blockade; single-electron tunneling
81.07.Ta Quantum dots
81.16.Ta Atom manipulation

Irradiation-induced formation of nanoparticles in cadmium niobate pyrochlore

W. Jiang, W. J. Weber, J. S. Young, and L. A. Boatner

Appl. Phys. Lett. 80, 670 (2002); http://dx.doi.org/10.1063/1.1445808 (3 pages) | Cited 5 times

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Sequential irradiation with 3 MeV He+ and 10 MeV C3+ ions performed at T = 150 K produces two separate amorphous buried layers in cadmium niobate pyrochlore single crystals. Further irradiation at room temperature results in the formation of nanometer-scale particles in the amorphized regions. An ion-cleaving technique was used to facilitate the observation of these nanoparticles by using scanning electron microscopy. Complete granulation with particle sizes ranging from 30 to 150 nm was observed. X-ray energy-dispersive spectrometry analysis indicates that the numerically large population of smaller particles ( ∼ 50 nm) contains a high Cd content ( ∼ 70%) and the numerically smaller population of larger particles (>100 nm) contains negligible Nb with a Cd-to-O ratio of about 1:0.54.© 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
61.80.Jh Ion radiation effects
61.82.Ms Insulators
64.70.Nd Structural transitions in nanoscale materials

Production of nanostructures of silicon on silicon by atomic self-organization observed by scanning tunneling microscopy

D. Jones and V. Palermo

Appl. Phys. Lett. 80, 673 (2002); http://dx.doi.org/10.1063/1.1445813 (3 pages) | Cited 10 times

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The possibility of exploiting the self-organization of mobile silicon atoms on silicon surfaces during ultrahigh vacuum thermal annealing for the construction of silicon-on-silicon structures is demonstrated. Rearrangement of the surface during thermal decomposition of an oxide layer can be controlled allowing the growth of primary structures surrounded by voids which can then be seeded by adsorbed gas molecules for the subsequent growth of secondary structures around the primary one. The controlled growth of these structures could find possible applications in Si-based microelectronic devices. © 2002 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
61.72.Cc Kinetics of defect formation and annealing
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Bandstructure modulation for carbon nanotubes in a uniform electric field

James O’Keeffe, Chengyu Wei, and Kyeongjae Cho

Appl. Phys. Lett. 80, 676 (2002); http://dx.doi.org/10.1063/1.1432441 (3 pages) | Cited 51 times

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A method to electronically modulate the energy gap and bandstructure of semiconducting carbon nanotubes is proposed. We investigate this bandstructure modulation mechanism using tight-binding and density functional theory (DFT). Results show that the energy gap of a semiconducting nanotube can be narrowed, when the tube is placed in an electric field perpendicular to the tube axis. In contrast, Metallic tubes were found to exhibit a screening behavior, whereby free charge redistributes about the tube circumference as a result of the external field. In this case, the bandstructure shows little perturbation in response to an applied electric field. © 2002 American Institute of Physics.
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73.22.Dj Single particle states
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
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