Noritaka Usami

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A current-injected silicon-based light-emitting device was fabricated on silicon-on-insulator (SOI) by embedding Ge self-assembled quantum dots into a silicon microdisk resonator with p-i-n junction for current-injection. Room-temperature resonant electroluminescence (EL) from Ge self-assembled quantum dots in the microdisk was successfully observed under(More)
We have studied the strain field around the 90° domains and misfit dislocations in PbTiO3/SrTiO3 (001) epitaxial thin films, at the nanoscale, using the geometric phase analysis (GPA) combined with high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark field--scanning transmission electron microscopy (HAADF-STEM). The films(More)
The growth mechanism of Si-faceted dendrite was studied using an in situ observational technique. We directly observed the growth processes of Si-faceted dendrites from Si melts. It is found that triangular corners with an angle of 60 degrees are formed at the dendrite tip. We present an original growth model for faceted dendrites based on the experimental(More)
Quantum dots (QDs) have attracted much attention for use in photovoltaic applications because of their potential for overcoming the limits of conventional single-junction devices. One problem associated with solar cells using QDs is that the open-circuit voltage (V(oc)) always decreases with the addition of QDs with respect to the reference cell without(More)
A sub-10 nm, high-density, periodic silicon nanodisk (Si-ND) array with a SiC interlayer has been fabricated using a new top-down process that involves a 2D array of a bio-template etching mask and damage-free neutral beam etching. Optical and electrical measurements were carried out to clarify the formation of mini-bands due to wavefunction coupling. We(More)
We propose a novel solar cell structure with photonic nanocrystals coupled to quantum dots (QDs) for advanced management of photons and carriers. The photonic nanocrystals at the surface create an extra interaction between the photons and the QDs, which promotes light trapping. Photo-generated carriers can be efficiently transported by preparing vertically(More)
The GISAXS intensity from buried Ge nanodots have been examined both by GISAXS/reflectivity measurements and also simulations with Distorted Wave Born Approximation (DWBA). The validity and the condition of using Born Approximation (BA) are discussed from the simulations based on the layer structures modelled from a reflectivity analysis. As expected in the(More)
Alain Fave1, Tetyana Nychyporuk1, Stéphane Bastide2, Mustapha Lemiti1, Noritaka Usami3 1 Institut des Nanotechnologies de Lyon (INL), UMR CNRS 5270, Université de Lyon INSA de Lyon, Bât Blaise Pascal, 7, avenue Jean Capelle, 69621 Villeurbanne Cedex, France 2 Institut de Chimie et des Matériaux Paris-Est ; 2-8, rue Henri Dunant, 94320 Thiais, France 3(More)
Grazing-incidence small-angle X-ray scattering (GISAXS) measurements with soft X-rays have been applied to Ge nanodots capped with a Si layer. Spatially anisotropic distribution of nanodots resulted in strongly asymmetric GISAXS patterns in the qy direction in the soft X-ray region, which have not been observed with conventional hard X-rays. However, such(More)
We fabricated a three-dimensional (3D) stacked Si nanodisk (Si-ND) array with a high aspect ratio and uniform size by using our advanced top-down technology consisting of bio-template and neutral beam etching processes. We found from conductive atomic microscope measurements that conductivity became higher as the arrangement was changed from a single Si-ND(More)