Theory of Pressure Effects on Silicon Nanocrystallites

1996 ◽  
Vol 452 ◽  
Author(s):  
G. Allan ◽  
C. Delerue ◽  
M. Lannoo
Keyword(s):  
Quantum Confinement ◽  
Radiative Recombination ◽  
Local Density ◽  
Tight Binding ◽  
Pressure Effects ◽  
Radiative Recombination Rate ◽  
Electron Hole ◽  
Silicon Nanocrystallites ◽  
Semi Empirical ◽  
Confinement Model

AbstractPressure effects on silicon nanocrystallites are calculated using semi-empirical tight-binding and ab-initio local density calculations. Using the confinement model in porous silicon a red shift of the luminescence energy with increasing pressure is obtained. Quantum confinement in BC8 phase silicon nanocrystallites obtained after release of high pressure are also studied. It increases the cluster gap and also enhances the electron-hole radiative recombination rate.

Possibility of Self-Trapped Excitons in Silicon Nanocrystallites

1995 ◽  
Vol 405 ◽  
Author(s):  
G. Allan ◽  
C. Delerue ◽  
M. Lannoo
Keyword(s):  
Quantum Confinement ◽  
Silicon Oxide ◽  
Light Emission ◽  
Local Density ◽  
Tight Binding ◽  
Localized States ◽  
Hydrogen Atoms ◽  
Quantum Confinement Effects ◽  
Silicon Nanocrystallites ◽  
Semi Empirical

AbstractWe present semi-empirical tight-binding and ab-initio local density calculations demonstrating the (meta)stability of self-trapped excitons in silicon nanocrystallites. These are obtained not only for surface dimer bonds passivated for instance by hydrogen atoms or by silicon oxide but also for “normal” nearest-neighbors bonds. Light emission from these trapped excitons is predicted in the infrared or in the visible. We are thus led to the interpretation that part of the luminescence is due to such localized states while optical absorption is characteristic of quantum confinement effects. These conclusions should extend to other semiconductor crystallites.

Luminescent Amorphous Silicon Layers

1997 ◽  
Vol 486 ◽  
Author(s):  
G. Allan ◽  
C. Delerue ◽  
M. Lannoo
Keyword(s):  
Electronic Structure ◽  
Amorphous Silicon ◽  
Radiative Recombination ◽  
Crystalline Silicon ◽  
Tight Binding ◽  
Blue Shift ◽  
Localized States ◽  
Structure Model ◽  
Radiative Recombination Rate ◽  
Tight Binding Approximation

AbstractThe electronic structure of amorphous silicon layers has been calculated within the empirical tight binding approximation using the Wooten-Winer-Weaire atomic structure model. We predict an important blue shift due to the confinement for layer thickness below 3 nm and we compare with crystalline silicon layers. The radiative recombination rate is enhanced by the disorder and the confinement but remains quite small. The comparison of our results with experimental results shows that the density of defects and localized states in the studied samples must be quite small.

Robust single-mode lasers based on hexagonal CdS microflakes

2020 ◽  
Vol 8 (32) ◽  
pp. 11201-11208
Author(s):  
Yang Mi ◽  
Yaoyao Wu ◽  
Jinchun Shi ◽  
Sheng-Nian Luo
Keyword(s):  
Radiative Recombination ◽  
Single Mode ◽  
Whispering Gallery Mode ◽  
Radiative Recombination Rate ◽  
Electron Hole ◽  
High Quality ◽  
Time Resolved ◽  
Whispering Gallery ◽  
Electron Hole Plasma ◽  
Time Resolved Photoluminescence

We have achieved single-mode whispering-gallery-mode lasing in CdS microflakes with sharp linewidth (∼0.12 nm) and high quality factor (∼4200). Such lasers are superior to previous CdS lasers in these lasing parameters. Through time-resolved photoluminescence measurements, electron–hole plasma recombination is established to be the lasing mechanism. The radiative recombination rate of CdS microflakes is enhanced by a factor of ∼4.7 due to the Purcell effect.

Effects of Structural Disorder on the Electronic Properties of Silicon: Tight-Binding Calculations of Grain Boundaries

1993 ◽  
Vol 297 ◽  
Author(s):  
M. Kohyama ◽  
R. Yamamoto
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Local Density ◽  
Tight Binding ◽  
Structural Disorder ◽  
Local Density Of States ◽  
Deep State ◽  
Amorphous Si ◽  
Semi Empirical ◽  
Twist Boundaries

The atomic and electronic structures of tilt and twist boundaries in Si have been calculated by using the transferable semi-empirical tight-binding (SETB) method, and the relations between the local structural disorder and the electronic properties of Si have been obtained clearly. The odd-membered rings and the four-membered rings induce the changes of the shape of the local density of states (LDOS). The bond distortions generate the peaks at the band edges in the LDOS, and greatly distorted bonds induce the weak-bond states inside the band gap. The three-coordinated defect generates a deep state in the band gap, which is much localized at the three-coordinated atom. The five-coordinated defect generates both deep and shallow states. The deep state is localized in the neighboring atoms except the five-coordinated atom, although the shallow states exist among the five-coordinated atom and the neighboring atoms. Configurations of boundaries are very effective in order to clarify the effects of the local structural disorder in amorphous SI.

GaAs Total Energy Tight Binding Hamiltonians for use in Molecular Dynamics

1990 ◽  
Vol 193 ◽  
Author(s):  
Jeremy Broughton ◽  
Mark Pederson ◽  
Dimitrios Papaconstantopoulos ◽  
David Singh
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Tight Binding ◽  
Large Data ◽  
Matrix Elements ◽  
Energy Matrix ◽  
Self Consistent ◽  
Total Energies ◽  
Local Density Functional ◽  
Semi Empirical

ABSTRACTA self-consistent non-orthogonal semi-empirical tight binding Hamiltonian is proposed for GaAs, or any sp system, which is simple, reliable, transferable, accurate and fast to evaluate. Matrix elements are functions of charges, distances between atoms and simple cosines of angles between s and p-electron densities and interatomic vectors which maintain the simplicity of Slater-Koster parameterizations. The tight binding scheme is fit against a large data base of local density functional derived total energies for systems of differing coordination and geometry. The Hamiltonian fulfills the correct Virial constraint, invokes the physically correct relationship between overlap and kinetic energy matrix elements and defines charges via Mulliken or Löwdin schemes. Such Hamiltonians will allow the reliable simulation of statistical mechanically interesting systems of order hundred or more atoms over physically useful periods of time of order tens to hundreds of thousands of time steps within not unreasonable supercomputer budgets.

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