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25 Nov 2002

Volume 81, Issue 22, pp. 4103-4293

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Exciton–exciton interaction engineering in coupled GaN quantum dots

Sergio De Rinaldis, Irene D’Amico, and Fausto Rossi

Appl. Phys. Lett. 81, 4236 (2002); http://dx.doi.org/10.1063/1.1519353 (3 pages) | Cited 13 times

Online Publication Date: 19 November 2002

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We present a fully three-dimensional study of the multiexciton optical response of vertically coupled GaN-based quantum dots via a direct-diagonalization approach. The proposed analysis is crucial in understanding the fundamental properties of few-particle/exciton interactions and, more important, may play an essential role in the design/optimization of semiconductor-based quantum information processing schemes. In particular, we focus on interdot exciton–exciton coupling, the key ingredient in recently proposed all-optical quantum processors. Our analysis demonstrates that there is a large window of realistic parameters for which both biexcitonic shift and oscillator strength are compatible with such implementation schemes. © 2002 American Institute of Physics.
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73.21.La Quantum dots
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Gg Exciton-mediated interactions
03.67.Lx Quantum computation architectures and implementations
78.67.Hc Quantum dots

Fabrication of dot matrix, comb, and nanowire structures using laser ablation by interfered femtosecond laser beams

Yoshiki Nakata, Tatsuo Okada, and Mitsuo Maeda

Appl. Phys. Lett. 81, 4239 (2002); http://dx.doi.org/10.1063/1.1522481 (3 pages) | Cited 25 times

Online Publication Date: 19 November 2002

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A line of periodic dot structure with an interval of 6.25 μm on a gold thin film was fabricated with a single shot of interfered femtosecond laser beams split by a diffraction beam splitter. The total length of the structure was 6 mm. In addition, dot matrix and comb structures were fabricated with transportation of samples at an arbitrary speed during the process. The samples worked as transmission and reflection gratings. In addition, nanowires were fabricated by peeling the comb structure, of which the thickness was 200 nm. © 2002 American Institute of Physics.
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81.16.Mk Laser-assisted deposition
42.79.Dj Gratings

Vacuum thermionic refrigeration with a semiconductor heterojunction structure

Yoshikazu Hishinuma, Boris Y. Moyzhes, Theodore H. Geballe, and Thomas W. Kenny

Appl. Phys. Lett. 81, 4242 (2002); http://dx.doi.org/10.1063/1.1523653 (3 pages) | Cited 13 times

Online Publication Date: 19 November 2002

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We consider possibilities for refrigeration by emission of electrons into vacuum using a semiconductor layered heterostructure and applying electric field in the order of 106 V/cm. Under the influence of a strong electric field, the height of the vacuum potential barrier is significantly reduced due to the Schottky effect and penetration of electric field into the semiconductor layer allowing high emission current. Joule heating inside the semiconductor layer can be minimized by creating a heterostructure with decreasing electron affinity from the metal–semiconductor boundary to the semiconductor–vacuum boundary. We find it is possible to obtain large Peltier currents while minimizing joule heating in the semiconductor. We find it is realistic to expect cooling of 10–100 W/cm2 at room temperature and down to 100 K by adjusting the thickness, and electron affinities of the semiconductor within practical ranges. © 2002 American Institute of Physics.
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79.40.+z Thermionic emission
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Breaking and restoring a molecularly bridged metal∣quantum dot junction

Z. Hens, D. V. Tallapin, H. Weller, and D. Vanmaekelbergh

Appl. Phys. Lett. 81, 4245 (2002); http://dx.doi.org/10.1063/1.1525396 (3 pages) | Cited 13 times

Online Publication Date: 19 November 2002

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Nanometer-sized insulating quantum dots (CdSe and ZnO) have been attached to a Au(111) substrate, using molecular bridges with thiol and carboxylate end functions. We demonstrate that the quantum dots can be probed by a scanning tunneling microscope at negative substrate bias. At positive bias, however, the gold–sulfur bond is broken and the quantum dots are transferred to the tip. Individual CdSe quantum dots can be picked up by the tip and displaced on the substrate in a controlled way. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
81.05.Dz II-VI semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.Ct Interface structure and roughness

Si rings, Si clusters, and Si nanocrystals—different states of ultrathin SiOx layers

L. X. Yi, J. Heitmann, R. Scholz, and M. Zacharias

Appl. Phys. Lett. 81, 4248 (2002); http://dx.doi.org/10.1063/1.1525051 (3 pages) | Cited 70 times

Online Publication Date: 19 November 2002

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Amorphous SiO/SiO2 superlattices were prepared by reactive evaporation of SiO powder in an oxygen atmosphere. Infrared absorption and photoluminescence spectra were measured as a function of annealing temperature. Three photoluminescence emission bands were observed. A band centered at 560 nm is present in as-prepared samples and vanishes for annealing above 700 °C. The second band around 760 nm to 890 nm is detected for annealing temperatures above 500 °C. A strong red luminescence is observed for annealing temperatures above 900 °C. The origin of the different photoluminescence bands and different states of the phase separation of ultrathin SiOx layers is discussed. © 2002 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.55.Hx Other solid inorganic materials
68.65.Cd Superlattices
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
61.46.-w Structure of nanoscale materials

Measurement of relaxation between polarization eigenstates in single quantum dots

T. H. Stievater, Xiaoqin Li, T. Cubel, D. G. Steel, D. Gammon, D. S. Katzer, and D. Park

Appl. Phys. Lett. 81, 4251 (2002); http://dx.doi.org/10.1063/1.1526912 (3 pages) | Cited 23 times

Online Publication Date: 19 November 2002

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Low temperature relaxation of excitons between polarization eigenstates in single interface fluctuation quantum dots is studied using copolarized and cross-polarized transient differential transmission spectroscopy. The measured spin relaxation times are on the order of ∼100 ps. Such a spin relaxation time is longer than the reported times for thin quantum wells, but considerably shorter than the predicted times for interface fluctuation quantum dots. © 2002 American Institute of Physics.
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73.21.La Quantum dots
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
78.67.Hc Quantum dots

Surface-mediated structural transformation in CdTe nanoparticles dispersed in SiO2 thin films

P. Babu Dayal, B. R. Mehta, Y. Aparna, and S. M. Shivaprasad

Appl. Phys. Lett. 81, 4254 (2002); http://dx.doi.org/10.1063/1.1524697 (3 pages) | Cited 11 times

Online Publication Date: 19 November 2002

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Cadmium telluride nanoparticles dispersed in silicon dioxide thin films have been grown by magnetron sputtering technique followed by thermal annealing. The effect of thermal annealing conditions on the structure of the surface layer and the nanoparticle core has been studied. A structural transformation in the nanoparticle core mediated solely by surface effects has been observed for the first time in any nanoparticle system. The presence of a crystalline cadmium tellurium oxide layer modifies the crystal structure of the cadmium telluride nanoparticle core by introducing a large concentration of stacking faults. © 2002 American Institute of Physics.
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64.70.Nd Structural transitions in nanoscale materials
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
61.72.Cc Kinetics of defect formation and annealing
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.Nn Stacking faults and other planar or extended defects
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