Computation of the Porous Silicon Dielectric Function in the Supercell Model and Comparison with Experiment

1999 ◽  
Vol 579 ◽  
Author(s):  
J. Tagüeeña-Martínez ◽  
Y.G. Rubo ◽  
M. Beltrán ◽  
C. Wang ◽  
M. Cruz
Keyword(s):  
Porous Silicon ◽  
Dielectric Function ◽  
Imaginary Part ◽  
Absorption Edge ◽  
Tight Binding ◽  
Pore Morphology ◽  
Hydrogen Atoms ◽  
Comparison With Experiment ◽  
Supercell Model

ABSTRACTWe present the results for the imaginary part of the dielectric function of porous silicon, which were obtained with the tight-binding 128–atom supercell model for different porosities. The supercells have been chosen to allow the interconnection of the Si skeleton. We have analyzed also the effects of pore morphology. We have found that, at a fixed porosity, the developing of the surface, resulting in the increase of saturating hydrogen atoms, leads to a noticeable blueshift of the absorption edge.

A Microscopic Model for the Dielectric Function of Porous Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
M. Cruz ◽  
M. R. Beltran ◽  
C. Wang ◽  
J. Tagüeña-Martinez
Keyword(s):  
Porous Silicon ◽  
Dielectric Function ◽  
Tight Binding ◽  
Microscopic Analysis ◽  
Basis Set ◽  
Hydrogen Atoms ◽  
Nano Structures ◽  
Materials Research ◽  
Si Films ◽  
Supercell Model

AbstractMicro and nano-structures have opened a new area in materials research since they present interesting phenomena such as efficient luminescence and localization of carriers. An important example of these new materials is porous silicon (PS). It is considered that the quantum confinement is an essential cause of the opto-electronic properties of PS [1], thus microscopic analysis should be performed. We have developed a supercell model to study PS with a tight-binding Hamiltonian, where an sp3s* basis set is used. In an otherwise perfect silicon structure empty columns of atoms are produced and passivated with hydrogen atoms [2]. In this work we calculate the dielectric function and compare it against experimental data for bulk c-Si, ultrathin c-Si films and PS. We discuss the importance of considering the relaxation of the electron wavevector (k) conservation in order to include disorder effects in PS.

Electronic and Vibrational Properties of Porous Silicon

2009 ◽  
Vol 5 ◽  
pp. 153-160 ◽  
Author(s):  
Miguel Cruz-Irisson ◽  
Chu Min Wang
Keyword(s):  
Experimental Data ◽  
Porous Silicon ◽  
Band Structure ◽  
Dielectric Function ◽  
Electronic Band Structure ◽  
Tight Binding ◽  
Hydrogen Atoms ◽  
Electronic Band ◽  
Supercell Model ◽  
Ordered Porous

For ordered porous silicon, the Born potential and phonon Green’s functions are used to investigate its Raman response, while the electronic band structure and dielectric function are studied by means of a sp3s* tight-binding supercell model, in which periodical pores are produced by removing columns of atoms along [001] direction from a crystalline Si structure and the pores surfaces are passivated by hydrogen atoms for the electronic band structure calculations. This supercell model emphasizes the interconnection between silicon nanocrystals, delocalizing the electronic and phononic states. However, the results of both elementary excitations show a clear quantum confinement signature, which is contrasted with that of nanowire systems. In addition, ab-initio calculations of small supercells are performed in order to verify the tight-binding results. The calculated dielectric function is compared with experimental data. Finally, a shift of the highest-frequency Raman peak towards lower energy is observed, in agreement with the experimental data.

Quantum Effects on the Dielectric Function of Porous Silicon

2000 ◽  
Vol 638 ◽  
Author(s):  
M. Cruz ◽  
S. F. Díaz ◽  
C. Wang ◽  
Y. G. Rubo ◽  
J. Tagüeña-Martínez
Keyword(s):  
Porous Silicon ◽  
Dielectric Function ◽  
Imaginary Part ◽  
Effective Medium Theory ◽  
Tight Binding ◽  
Exact Result ◽  
Effective Medium ◽  
Tight Binding Approximation ◽  
Medium Theory ◽  
Microscopic Models

AbstractIn this work, the imaginary part of the dielectric function of porous silicon is studied by means of both the tight-binding and the effective medium approaches, in the latter exact result is obtained for the case of 50% porosity. Within the tight-binding approximation, the dielectric function is calculated by using the interconnected and chessboard-like supercell models for the Si skeleton. These microscopic models give quantitatively similar results, which are by a factor of three larger than those from the effective medium theory.

Electronic Properties of Porous Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
M. R. Beltran ◽  
J. Tagüeña-Martinez ◽  
M. Cruz ◽  
C. Wang
Keyword(s):  
Porous Silicon ◽  
Band Gap ◽  
Tight Binding ◽  
Perfect Crystal ◽  
Energy Band Structure ◽  
Basis Set ◽  
Pore Morphology ◽  
Hydrogen Atoms ◽  
Direct Band Gap ◽  
Direct Band

ABSTRACTPorous silicon (PS) has been extensively studied in recent years. The origin of its luminescence has been a subject of debate. This work attempts to give some insight towards the understanding of this phenomenon, studying the behaviour of the energy band structure of PS as a function of the pore morphology and distribution, for a given porosity. The porous structure is modeled as empty columns of different sizes and shapes, produced into san otherwise silicon perfect crystal. The columns are passivated with hydrogen atoms. A tight-binding Hamiltonian on an ; sp3:s* basis set is applied onto a supercell. Due to the simplicity of the model, morphology effects can be analyzed. The results show that the band :gap and the nature of the 'States at the top of the valence band depend on the morphology. Furthermore, we also discuss the shift of the conduction band minimum towards the gamma point, producing an almost direct band gap, as the pore distribution changes.

Electric Field Effect on the Imaginary Part of the Dielectric Function in Highly Anisotropic Crystals

1974 ◽  
Vol 36 (1) ◽  
pp. 179-186 ◽  
Author(s):  
Yoshiro Sasaki ◽  
Chihiro Hamaguchi ◽  
Akihiro Morotani ◽  
Junkichi Nakai
Keyword(s):  
Electric Field ◽  
Dielectric Function ◽  
Imaginary Part ◽  
Field Effect ◽  
Electric Field Effect

Evidence of x-ray absorption-edge shift as a function of luminescence wavelength in porous silicon

2000 ◽  
Vol 62 (15) ◽  
pp. 9911-9914 ◽  
Author(s):  
G. Dalba ◽  
N. Daldosso ◽  
P. Fornasini ◽  
M. Grimaldi ◽  
R. Grisenti ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Absorption Edge ◽  
X Ray ◽  
Absorption Edge Shift ◽  
X Ray Absorption

Pore morphology influence on catalytic turn-over for enzyme activated porous silicon matrices

1998 ◽  
Vol 330 (2) ◽  
pp. 161-166 ◽  
Author(s):  
Johan Drott ◽  
Lars Rosengren ◽  
Kjell Lindström ◽  
Thomas Laurell
Keyword(s):  
Porous Silicon ◽  
Pore Morphology ◽  
Turn Over ◽  
Morphology Influence

Probing Optical Transitions in Porous Silicon by Reflectance Spectroscopy in the Near Infrared, Visible and UV

1994 ◽  
Vol 358 ◽  
Author(s):  
W. Theiβ ◽  
R. Arens-Fischer ◽  
M. Arntzen ◽  
M.G. Berger ◽  
S. Frohnhoff ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Dielectric Function ◽  
Near Infrared ◽  
Solid Phase ◽  
Pore Wall ◽  
Reflectance Spectroscopy ◽  
Wall Material ◽  
Bulk Silicon ◽  
Band Structure Calculations ◽  
Structure Calculations

ABSTRACTReflectance spectroscopy has been used to obtain the dielectric function of the solid phase of porous silicon. The method is based on a fit of a parameterized dielectric function model to measured spectra. A crucial step in the procedure is the 'dielectric averaging' of the microscopic dielectric function of the pore wall material to the macroscopic effective dielectric function which governs the optical properties.Results are given for heavily and moderately p-doped samples of various porosities. For the latter large differences to bulk silicon have been found. The obtained dielectric functions are compared to the results of band structure calculations taken from literature.

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