Search results for "conductor"
showing 10 items of 1270 documents
Photochemical Size Reduction of CdSe and CdSe/ZnS Semiconductor Nanoparticles Assisted by nπ* Aromatic Ketones
2009
A novel effect of n pi* aromatic ketones on the quantum dots optical properties is reported. By controlling experimental conditions such as time of irradiation, presence of air in the media, hydrogen donor capacity of the solvent, and irradiation wavelength, core and core-shell CdSe QDs can be resized as convenient.
Temperature dependence of the E2h phonon mode of wurtzite GaN/AlN quantum dots
2008
Raman scattering has been used to study the temperature dependence of the frequency and linewidth of the E2h phonon mode of GaN/AlN quantum dot stacks grown on 6H-SiC. The evolution of the nonpolar phonon mode was analyzed in the temperature range from 80 to 655 K for both quantum dots and barrier materials. The experimental results are interpreted by comparison with a model that takes into account symmetric phonon decay and the different thermal expansions of the constituents of the heterostructure. We find a small increase in the anharmonic parameters of the phonon modes in the heterostructure with respect to bulk. jorbumar@alumni.uv.es Alberto.Garcia@uv.es Ana.Cros@uv.es
Raman study of self-assembled InAs/InP quantum wire stacks with varying spacer thickness
2008
http://link.aip.org/link/?JAPIAU/104/033523/1
Oscillator strength reduction induced by external electric fields in self-assembled quantum dots and rings
2007
We have carried out continuous wave and time resolved photoluminescence experiments in self-assembled In(Ga)As quantum dots and quantum rings embedded in field effect structure devices. In both kinds of nanostructures, we find a noticeable increase of the exciton radiative lifetime with the external voltage bias that must be attributed to the field-induced polarizability of the confined electron hole pair. The interplay between the exciton radiative recombination and the electronic carrier tunneling in the presence of a stationary electric field is therefore investigated and compared with a numerical calculation based on the effective mass approximation.
Correlation between optical properties and barrier composition in InxGa1−xP/GaAs quantum wells
1998
9 páginas, 11 figuras.
Optical active centres in ZnO samples
2006
Abstract In recent years, there has been a resurgence in the interest in the use of ZnO (Eg ∼ 3.37 eV) as a material for a wide range of opto-emitter applications spanning visible and short wavelengths. Bulk, thin films and nanomaterials obtained using different synthesis methods have been investigated for optoelectronic and biotechnological device applications. Nominally undoped bulk samples typically present a myriad-structured near-band-edge recombination, mainly due to free/bound excitons and donor–acceptor pair transitions. Furthermore, deep level emission due to intrinsic defects and extrinsic impurities, such as transition metal ions, are commonly observed in different grades of bulk…
Electrochemical Deposition Mechanism for ZnO Nanorods: Diffusion Coefficient and Growth Models
2011
Fabrication of nanostructured ZnO thin films is a critical process for many applications based on semiconductor devices. So on understanding of the electrochemical deposition mechanism is also fundamental for knowing the optimal conditions on growth of ZnO nanorods by electrodeposition. In this paper the electrochemical mechanism for ZnO nanorods formation is studied. Results are based on the evolution of the diffusion coefficient using the Cotrell equation, and different growth models proposed by Scharifcker and Hills for nucleation and growth.
High-Frequency Experimental Characterization and Modeling of Six Pack IGBTs Power Modules
2016
In this paper, a method to characterize the high-frequency (HF) behavior of six pack insulated gate bipolar transistors (IGBTs) power module (PM) is presented. The method is based on experimental measurements at the external pins of the device and it allows one to extract internal inductive and capacitive parasitic coupling without the knowledge of structural and physical parameters of the PM. The HF model of a six pack IGBTs PM has been developed, in the frequency range of 150 kHz-30 MHz, and it has been implemented in MATLAB environment. The method has been experimentally validated by comparing the frequency behavior of the PM with the simulated response. Moreover, the HF conducted distur…
Enhanced light scattering in Si nanostructures produced by pulsed laser irradiation
2013
An innovative method for Si nanostructures (NS) fabrication is proposed, through nanosecond laser irradiation (lambda = 532 nm) of thin Si film (120 nm) on quartz. Varying the laser energy fluences (425-1130 mJ/cm(2)) distinct morphologies of Si NS appear, going from interconnected structures to isolated clusters. Film breaking occurs through a laser-induced dewetting process. Raman scattering is enhanced in all the obtained Si NS, with the largest enhancement in interconnected Si structures, pointing out an increased trapping of light due to multiple scattering. The reported method is fast, scalable and cheap, and can be applied for light management in photovoltaics. (C) 2013 AIP Publishin…
Modulated Crystal Structure and Electronic Properties of Semiconductor Cu47Si91P144
2000
Crystals of the copper silicon phosphide were synthesized by the iodine gas transport technique. The x-ray single crystal methods revealed a big superstructure with the lattice parameters a = b = 44.510 and c = 20.772 A and a basic tetragonal substructure with a = 3.7092 and c = 5.1930 A. Analysis of the intensities showed that the superstructure has a 1/2,1/2,1/2 tetragonal substructure with a = 22.255 and c = 10.386 A. This 1/2,1/2,1/2 substructure (Cu47Si91P144) and the basic tetragonal structure (Cu0.71Si1.29P2) were solved by the direct methods and refined in the I4m2 space group. The phosphide is a semiconductor with a small energy gap of 0.0269(1) eV. The electrical properties are co…