scholarly journals Moments-based tight-binding calculations of local electronic structure in InAs/GaAs quantum dots for comparison to experimental measurements

2006 ◽  
Vol 88 (5) ◽  
pp. 053109 ◽  
Author(s):  
Jun-Qiang Lu ◽  
H. T. Johnson ◽  
V. D. Dasika ◽  
R. S. Goldman
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Tight Binding ◽  
Experimental Measurements ◽  
Local Electronic Structure

Local Electronic Structure and Short-Range Order in a Computer Simulated Amorphous Metal

1991 ◽  
Vol 02 (01) ◽  
pp. 232-237 ◽  
Author(s):  
A.Ya. BELENKII ◽  
M.A. FRADKIN
Keyword(s):  
Electronic Structure ◽  
Short Range ◽  
Short Range Order ◽  
Local Density ◽  
Tight Binding ◽  
Amorphous Metal ◽  
Range Order ◽  
Tight Binding Approximation ◽  
Electronic Parameters ◽  
Local Electronic Structure

The relationship between topological short-range order and a local electronic structure was analyzed in the computer model of an amorphous metal. The model, obtained by means of the original self-consistent cluster simulation procedure was studied with the use of Voronoi tesselation, the distribution of the atomic level stresses and the icosahedral order parameters. It was found that a marked correlation exists within 2 atomic parameter groups, one of which corresponds to the local dilatation and the other to the spherical symmetry distortion. The local density of electronic d-states (DOS) and the distribution of the electronic parameters was analyzed. The local electronic structure, calculated within the tight-binding approximation, appears to depend on the local atomic order by two-fold means: the interatomic distances decrease leads to the increase of the local bandwidth, and the icosahedral configuration distortion reduces the DOS at the Fermi level. The study of the local configurations stability shows, that the most stable configurations are the slightly distorted icosahedra.

Simulation of InAsSb/InGaAs Quantum Dots for Optical Device Applications

2004 ◽  
Vol 851 ◽  
Author(s):  
Paul von Allmen ◽  
Seungwon Lee ◽  
Fabiano Oyafuso
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Band Gap ◽  
Atmospheric Chemistry ◽  
Energy Gap ◽  
Tight Binding ◽  
Atomic Interaction ◽  
Optical Detectors ◽  
Wide Range ◽  
Device Applications

ABSTRACTSelf-assembled InAsSb/InGaAs quantum dots are candidates for optical detectors and emitters in the 2–5 micron band with a wide range of applications for atmospheric chemistry studies. It is known that while the energy band gap of unstrained bulk InAs1−xSbx is smallest for x=0.62, the biaxial strain for bulk InAs1−xSbx grown on In0.53Ga0.47As shifts the energy gap to higher energies and the smallest band gap is reached for x=0.51. The aim of the present study is to examine how the electronic confinement in the quantum dots modifies these simple considerations. We have calculated the electronic structure of lens shaped InAs1−xSbx quantum dots with diameter 37 nm and height 4 nm embedded in a In0.53Ga0.47As matrix of thickness 7 nm and lattice matched to an InP buffer. The relaxed atomic positions were determined by minimizing the elastic energy obtained from a valence force field description of the inter-atomic interaction. The electronic structure was calculated with an empirical tight binding approach. For Sb concentrations larger than x=0.5, it is found that the InSb/ In0.53Ga0.47As heterostructure becomes type II leading to no electron confined in the dot. It is also found that the energy gap decreases with increasing Sb content in contradiction with previous experimental results. A possible explanation is a significant variation is quantum dot size with Sb content.

A Tight Binding Model for the Density of States of Graphite-like Structures, Calculated using Green's Functions

1993 ◽  
Vol 46 (5) ◽  
pp. 601 ◽  
Author(s):  
BA McKinnon ◽  
TC Choy
Keyword(s):  
Electronic Structure ◽  
Carbon Fibre ◽  
Density Of States ◽  
Tight Binding ◽  
Analytic Solutions ◽  
Elliptic Integrals ◽  
Experimental Measurements ◽  
Tight Binding Model ◽  
Binding Model ◽  
Densities Of States

The electronic structure of graphite-like materials is investigated within the framework of the tight binding model. The densities of states of simple hexagonal and Bernal graphite are calculated, induding two layer (2D) and bulk (3D) cases. The calculation employs Green's function techniques, resulting in essentially analytic solutions in terms of elliptic integrals. The Bernal density of states is found to agree qualitatively with experimental measurements and the extension of our studies to surface effects and carbon fibre structures is also discussed.

LOCAL ELECTRONIC STRUCTURE OF Tl2Ca2Ba2Cu3O10 AND COMPARISON WITH LA-OXIDES AND Y-OXIDES

1990 ◽  
Vol 04 (09) ◽  
pp. 1537-1549 ◽  
Author(s):  
HUAI-YU WANG ◽  
FU-SUI LIU ◽  
EN-GE WANG ◽  
CHONG-YU WANG
Keyword(s):  
Electronic Structure ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
The Other ◽  
Tight Binding Approximation ◽  
Densities Of States ◽  
Local Electronic Structure ◽  
Electronic Densities

Local electronic densities of states of Tl 2 Ca 2 Ba 2 Cu 3 O 10 (2223) are calculated by tight-binding approximation. The nearest and the next-nearest neighbor transitions are considered, and the results are compared with each other. After the latter is considered, the densities of states are smoothened and the semiconductor-like characteristic of the Tl-O layers disappears. Through comparison of 2223 with the other two high Tc ceramics La 2−x Sr x CuO 4 and YBa 2 Cu 3 O 7−x, it is believed that they have the same leading superconductive mechanism besides inter-plane interactions.

ELECTRONIC STRUCTURE CALCULATIONS ON MoTe2 WITH ROTATED PLANES

2005 ◽  
Vol 19 (26) ◽  
pp. 3933-3943
Author(s):  
A. TLAHUICE ◽  
E. FLORES ◽  
D. H. GALVÁN
Keyword(s):  
Electronic Structure ◽  
Diffraction Pattern ◽  
Tight Binding ◽  
Electronic Structure Calculations ◽  
Experimental Measurements ◽  
Metallic Behavior ◽  
Tight Binding Method ◽  
Total Energies ◽  
Structure Calculations ◽  
Good Agreement

Electronic structure calculations have been carried out using Extended Hückel tight-binding method for 2 H — MoTe 2 for the cases both unrotated and with rotated planes. It has been found that relative rotations of the tellurium layers ranging from 5 to 16 degrees have the same total energies and total energies/atom as the unrotated structure. Moreover, an increased in metallic behavior has been observed, as long as the degrees of rotated planes are increased. Finally, good agreement has been found among previous experimental measurements in the diffraction pattern of irradiated MoTe 2 and our calculated 5, 6 and 7 degrees of rotations.

Electronic Structure Boundary Value Problems Without All of the Atoms

1998 ◽  
Vol 538 ◽  
Author(s):  
H. T. Johnson ◽  
R. Phillips ◽  
L. B. Freund
Keyword(s):  
Finite Element ◽  
Electronic Structure ◽  
Boundary Value Problems ◽  
Boundary Value ◽  
Tight Binding ◽  
Finite Element Program ◽  
Quasicontinuum Method ◽  
Finite Element Package ◽  
Element Program ◽  
Local Electronic Structure

AbstractA mixed atomistic/continuum technique, in the spirit of the quasicontinuum method, is formulated and used to solve boundary value problems in strained semiconductor structures in which the mechanical fields and the local electronic structure are fully coupled. The technique is implemented by means of a standard structural mechanics finite element package. Within each element in the mesh, tight binding calculations are made for mechanical properties based on the local electronic structure. The finite element program calculates equilibrium mechanical fields based on this atom-istic constitutive information; the underlying electronic properties can then be extracted at the element level. The technique is demonstrated by examining several simple plane strain boundary value problems for coherently strained silicon.

Electronic Structure of InN/GaN Quantum Dots: Multimillion-Atom Tight-Binding Simulations

2010 ◽  
Vol 57 (1) ◽  
pp. 164-173 ◽  
Author(s):  
Shaikh Ahmed ◽  
Sharnali Islam ◽  
Shareef Mohammed
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Tight Binding

EELS Measurement of the Local Electronic Structure of Copper Atoms Segregated to Aluminum Grain Boundaries

1996 ◽  
Vol 54 ◽  
pp. 342-343
Author(s):  
S.J. Splinter ◽  
J. Bruley ◽  
P.E. Batson ◽  
D.A. Smith ◽  
R. Rosenberg
Keyword(s):  
Electronic Structure ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Thin Layers ◽  
Nominal Composition ◽  
Spatially Resolved ◽  
Service Lifetime ◽  
Heat Treated ◽  
Probe Size ◽  
Local Electronic Structure

It has long been known that the addition of Cu to Al interconnects improves the resistance to electromigration failure. It is generally accepted that this improvement is the result of Cu segregation to Al grain boundaries. The exact mechanism by which segregated Cu increases service lifetime is not understood, although it has been suggested that the formation of thin layers of θ-CuA12 (or some metastable substoichiometric precursor, θ’ or θ”) at the boundaries may be necessary. This paper reports measurements of the local electronic structure of Cu atoms segregated to Al grain boundaries using spatially resolved EELS in a UHV STEM. It is shown that segregated Cu exists in a chemical environment similar to that of Cu atoms in bulk θ-phase precipitates.Films of 100 nm thickness and nominal composition Al-2.5wt%Cu were deposited by sputtering from alloy targets onto NaCl substrates. The samples were solution heat treated at 748K for 30 min and aged at 523K for 4 h to promote equilibrium grain boundary segregation. EELS measurements were made using a Gatan 666 PEELS spectrometer interfaced to a VG HB501 STEM operating at 100 keV. The probe size was estimated to be 1 nm FWHM. Grain boundaries with the narrowest projected width were chosen for analysis. EDX measurements of Cu segregation were made using a VG HB603 STEM.

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