Home  About us  Contact
 

Quantum Confinement Effects (quantum + confinement_effects)

Distribution by Scientific Domains
Physics and Astronomy66%

Selected Abstracts

Hydrogen surface passivation of Si and Ge nanowires: A semiempirical approach

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2010
A. Miranda
Abstract A semiempirical nearest-neighbor tight-binding approach, that reproduces the indirect band gaps of elemental semiconductors, has been applied to study the electronic and optical properties of Si and Ge nanowires (NWs). The calculations show that Si-NWs keep the indirect bandgap whereas Ge-NWs changes into the direct bandgap when the wire cross section becomes smaller. Also, the band gap enhancement of Si-NWs showing to quantum confinement effects is generally larger than that of similar-sized Ge-NWs, confirming the larger quantum confinement effects in Si than in Ge when they are confined in two dimensions. Finally, the dependence of the imaginary part of the dielectric function on the quantum confinement within two different schemes: intra-atomic and interatomic optical matrix elements are applied. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2448,2454, 2010 [source]

Photoluminescence properties of GaAs nanowire ensembles with zincblende and wurtzite crystal structure

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010
B. V. Novikov
Abstract Self-standing III,V nanowires (NWs) are promising building blocks for future optoelectronic devices such as LEDs, lasers, photodetectors and solar cells. In this work, we present the results of low temperature photoluminescence (PL) characterization of GaAs NWs grown by Au-assisted molecular beam epitaxy (MBE), coupled with the transmission electron microscopy (TEM) structural analysis. PL spectra contain exci- ton peaks from zincblende (ZB) and wurtzite (WZ) crystal structures of GaAs. The peaks are influenced by the quantum confinement effects. PL bands corresponding to the exciton emission from ZB and WZ crystal phases are identified, relating to the PL peaks at 1.519 eV and 1.478 eV, respectively. The obtained red shift of 41 meV for WZ GaAs should persist in thin NWs as well as in bulk materials. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Determination of critical points on silicon nanofilms: surface and quantum confinement effects

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008
Emmanouil Lioudakis
Abstract In this work, we present a comprehensive study of the optical properties of nanocrystalline silicon films with thickness varied from 5 to 30 nm. Spectroscopic ellipsometry is employed to determine the dielectric functions of these films using a structural two-layer model based on the rigorous Airy formula. Our investigation gives an important insight of the origin of critical points for direct and indirect gaps of nanocrystalline silicon films as well as the evolution of them with decreasing the film thickness. The influence of the quantum confinement effect due to the nanoscale grain size and the surface vibrations at the interface on the optical properties are examined in detail. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Structure of small II-VI semiconductor nanoparticles: A new approach based on powder diffraction

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2007
Franziska Niederdraenk
Abstract In many cases of nanostructures a better understanding of the optical, electronic, and catalytic properties is hindered by a lack of detailed structural knowledge of sufficient quality. This is in particular true for very small nanoparticles (<5 nm) where quantum confinement effects play a dominant role. We introduce a novel method for the detailed structural analysis of such small nanoparticles, which includes not only the modeling of basic parameters like size, shape, and structure, but also allows to determine impurities and defects (like, e.g., stacking faults), stress and relaxation effects, etc. Distributions of basic parameters as the size distribution are also implemented by enabling ensemble averaging. Different examples obtained from CdS, ZnS and ZnO particles are presented and demonstrate the superiority of the new approach compared to simpler methods. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

InAsSb/InGaAs quantum nanostructures on InP (100) substrate: observation of 2.35 µm photoluminescence

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006
F. Doré
Abstract A theoretical and experimental study of the electronic properties of InAsSb quantum dots (QDs) grown on InP substrate is presented. Unstrained bulk InAsSb presents a direct gap between 0.1 eV to 0.35 eV, suitable for mid infrared emitters (3,5 µm). However, strain and quantum confinement effects may limit the extension of the emission spectrum of these nanostructures towards longer wavelengths. Various combinations of barrier materials are considered in the simulations. First photoluminescence spectroscopy experiments on molecular beam epitaxy (MBE) grown samples show promising results. Triple stacks of InAs QDs embedded in a GaInAsP alloy lattice matched to InP and grown by the Stranski-Krastanov mode exhibit room temperature (RT) luminescence at about 2 µm. Emission wavelengths as long as 2.35 µm have been observed at RT in a InAsSb/InGaAs/InP structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]