Extended Quantum Model for Porous Silicon Formation

1994 ◽  
Vol 358 ◽  
Author(s):  
H. Münder ◽  
St. Frohnhoff ◽  
M.G. Berger ◽  
M. Marso ◽  
M. Thönissen ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Doping Level ◽  
Tunneling Probability ◽  
Quantum Mechanical ◽  
Quantum Model ◽  
Electrochemical Dissolution ◽  
Quantum Mechanical Calculations ◽  
Model Calculations ◽  
Etching Parameters ◽  
Substrate Doping

ABSTRACTThe formation of porous silicon (PS) by electrochemical dissolution of bulk Si is described by a new model involving quantum mechanical calculations of the tunneling probability of holes through small crystallites (< 60 Å) into the electrolyte. This tunneling probability shows oscillations as a function of crystallite size. The presented model calculations are in agreement to the microstructure of p-PS — deduced from Raman measurements — as a function of etching parameters and substrate doping level.

Influence of Etching Time on Surface Structural Properties of p- and n- Type Porous Silicon Nanostructures by Photo-Electrochemical Anodic Etching

2012 ◽  
Vol 576 ◽  
pp. 511-515
Author(s):  
N.A. Asli ◽  
Maslihan Ain Zubaidah ◽  
S.F.M. Yusop ◽  
Khairunnadim Ahmad Sekak ◽  
Mohammad Rusop ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Crystalline Silicon ◽  
Surface Characteristic ◽  
Electrochemical Anodization ◽  
Silicon Nanostructures ◽  
Etching Time ◽  
Force Microscopy ◽  
Etching Parameters ◽  
P Type ◽  
Substrate Doping

Porous silicon nanostructures (PSiN) are nanoporous materials which consist of uniform network of interconnected pore. The structure of PSiN is depending on etching parameters, including current density, HF electrolyte concentration, substrate doping type and level. In this work, the results of a structural p-type and n-type of porous silicon nanostructures were investigated by Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM) is reported. Samples were prepared by photo-electrochemical anodization of p- and n-type crystalline silicon in HF electrolyte at different etching time. The surface morphology of PSiN was studied by FESEM with same magnification shown n-type surface form crack faster than p-type of PSiN. While the topography and roughness of PSiN was characterize by AFM. From topography shown the different etching time for both type PSiN produce different porosity and roughness respectively. There is good agreement between p- and n-type have different in terms of surface characteristic.

2,5,8,11-Tetra-tert-butyl-peri-xanthenoxanthene and its Dication Spectroelectrochemistry and Model Calculations on a Dioxa-22-π-system

1996 ◽  
Vol 51 (3) ◽  
pp. 377-380 ◽  
Author(s):  
Gernot Frenking ◽  
Anton Rieker ◽  
Josef Salbeck ◽  
Bernd Speiser
Keyword(s):  
Ab Initio ◽  
Radical Cation ◽  
Bathochromic Shift ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Model Calculations ◽  
Tert Butyl ◽  
Model Structures

Abstract Spectroelectrochemistry of 2,5,8,1 1-tetra-tert-butyl-peri-xanthenoxanthene 1 yields the UV/VIS spectra of the corresponding radical cation 1+ and dication 12+. The bathochromic shift for the dication 12+ relative to 1 and to the isoelectronic hydrocarbon anthanthrene (2) can be understood by quantum mechanical calculations (ab initio, AM1) of model structures.

Revised prediction of B1 to B2 phase transition pressures in YbN, YbP and YbAs

2005 ◽  
Vol 220 (8) ◽  
Author(s):  
Björn Winkler ◽  
Victor Milman
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
Density Functional ◽  
Structural Phase ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Model Calculations ◽  
B2 Phase

AbstractQuantum mechanical calculations based on density functional theory and a generalized gradient approx imation have been used to study the pressure-induced B1 to B2 structural phase transition in YbN, YbP and YbAs. The phase transitions are predicted to occur at 137 GPa in YbN, at 25 GPa in YbP, and at 20 GPa in YbAs. These values are significantly lower than those predicted by empirical poten tial model calculations. Bulk moduli are predicted to be 136, 70 and 63 GPa for YbN, YbP and YbAs, respectively.

Crystal Forms of Semisynthetic Ergot Alkaloid Terguride

2002 ◽  
Vol 67 (4) ◽  
pp. 479-489 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Ladislav Cvak ◽  
Alexandr Jegorov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ergot Alkaloid ◽  
Simplified Model ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray Diffraction ◽  
Torsion Angles ◽  
Crystal Forms ◽  
X Ray ◽  
Independent Molecules

Two new structures of semisynthetic ergot alkaloid terguride created by unusual number of symmetry-independent molecules were determined by X-ray diffraction methods at 150 K. Form A (monoclinic, P212121, Z = 12) contains three symmetry-independent terguride molecules and two molecules of water in the asymmetric part of the unit cell. The form CA (monoclinic, P21, Z = 8) is an anhydrate remarkable by the presence of four symmetry-independent molecules in the crystal structure. Conformations of twelve symmetry-independent molecules that were found in four already described terguride structures are compared with torsion angles obtained by ab initio quantum-mechanical calculations for the simplified model of N-cyclohexyl-N'-diethylurea.

Chemical accuracy from ‘Coulomb hole’ extrapolated molecular quantum-mechanical calculations

2001 ◽  
Vol 567-568 ◽  
pp. 375-384 ◽  
Author(s):  
K.L Bak ◽  
A Halkier ◽  
P Jørgensen ◽  
J Olsen ◽  
T Helgaker ◽  
...  
Keyword(s):  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Coulomb Hole
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