Hydrogen Density of States and Defects Densities in a-Si:H

1996 ◽  
Vol 420 ◽  
Author(s):  
S C Deane ◽  
M J Powell ◽  
J Robertson
Keyword(s):  
Valence Band ◽  
Density Of States ◽  
Unified Model ◽  
Band Tail ◽  
Hydrogen Density ◽  
The Creation

AbstractFurther details are given of a unified model of the hydrogen density of states and defect pool of a-Si:H. The model is compared to other defect models and extended to describe a-Si alloys and the creation of valence band tail states during growth.

States in the Gap of Improved a-Ge:H Studied by Photomodulation Spectroscopy

1991 ◽  
Vol 219 ◽  
Author(s):  
L. Chen ◽  
J. Tauc ◽  
D. Pang ◽  
W. A. Turner ◽  
W. Paul
Keyword(s):  
Glow Discharge ◽  
Valence Band ◽  
Density Of States ◽  
Pump Beam ◽  
Defect Density ◽  
Dangling Bond ◽  
Band Tail ◽  
Valence Bands

ABSTRACTThe photomodulation spectra of a-Ge:H of average photoelectronic quality(ημπ = 1 × 10-10cm2/V) and of improved quality (ημπ = 3 × 10-7cm2/V), produced under different plasma conditions in an r.f. diode reactor by glow discharge, were measured at 80K and are analyzed in analogy with earlier studies of a-Si:H. The spectra of the poorer material are dominated by transitions between dangling bond states and the conduction and valence bands. By contrast, the spectra of the better material require contributions of transitions from the band tail states, indicating that the reduced defect density has resulted in pump-beam induced quasi-Fermi levels reaching near the conduction and valence band edges. A very acceptable fit between plausible density-of-states distributions and the experimental spectra has been found.

The Density of States in Undoped and Doped Amorphous Silicon-Germanium Alloys Determined through Photoyield Spectroscopy

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Aljishi ◽  
Jin Shu ◽  
L. Ley
Keyword(s):  
Valence Band ◽  
Density Of States ◽  
Relative Position ◽  
Silicon Germanium ◽  
Lower Energy ◽  
Composition Range ◽  
Significant Shift ◽  
Band Tail ◽  
Defect Band ◽  
Amorphous Silicon Germanium

ABSTRACTPhotoelectron yield spectroscopy is used to study the occupied density of states (DOS) in undoped and doped a-Si, Ge:H alloys. We find a shift in the top of the valence band to lower energy as the Ge content is increased. The width of the defect band becomes abruptly narrower when Ge is initially introduced. This change is accompanied by a significant shift in the relative position of the Fermi level towards midgap. The defect peak tracks the valence band throughout the entire composition range. The intrinsic valence band tail in the alloys is found to be an exponential with a characteristic slope of 50 to 60 meV independent of composition. Boron and phosphorous doping affect the DOS of the alloys in a manner similar to that measured in a-Si:H.

Sensitization of the Holes Lifetime by the Addition of Dangling Bonds in a-Si:H

2001 ◽  
Vol 664 ◽  
Author(s):  
L.F. Fonseca ◽  
S. Z. Weisz ◽  
I. Balberg
Keyword(s):  
Valence Band ◽  
Important Implication ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
Defect States ◽  
Band Tail ◽  
Present Understanding

ABSTRACTThis paper is concerned with the phenomenon of the increase of the holes lifetime with the increase of the dangling bond concentration in a-Si:H. This rather surprising phenomenon that was observed, but not discussed, previously is shown to be a non-trivial effect which is based on the charged nature of the dangling bonds and a special scenario of the concentrations of the various defect states in the material. The most important implication of our study is that the charged dangling bonds can sensitize the valence band tail states, in contrast with the accepted roles of these types of states. The present understanding suggests that many new interesting phototransport phenomena can be found in a-Si:H.

scholarly journals Effect of band structure adjustment based of Cu site on the thermoelectric properties of BiCuSeO

2021 ◽  
Author(s):  
Bo Feng
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Effective Mass ◽  
Valence Band ◽  
Thermoelectric Properties ◽  
Density Of States ◽  
First Principles Calculation ◽  
Temperature Range ◽  
Ti Doping

Abstract The effect of Ti doped at Cu site on the thermoelectric properties of BiCuSeO was studied by experimental method and first principles calculation. The results show that Ti doping can cause the lattice contraction and decrease the lattice constant. Ti doping can increase the band gap and lengthen the Cu/Ti-Se bond, resulting in the decrease of carrier concentration. Ti doping can reduce the effective mass and the Bi-Se bond length, correspondingly improve the carrier mobility. Ti doping can decrease the density of states of Cu-3d and Se-4p orbitals at the top of valence band, but Ti-4p orbitals can obviously increase the density of states at the top of valence band and finally increase the electrical conductivity in the whole temperature range. With the decrease of effective mass, Ti doping would reduce the Seebeck coefficient, but the gain effect caused by the increase of electrical conductivity is more than the benefit reduction effect caused by the decrease of Seebeck coefficient, and the power factor shows an upward trend. Ti doping can reduce Young's modulus, lead to the increase of defect scattering and strain field, correspondingly reduce the lattice thermal conductivity and total thermal conductivity. It is greatly increased for the ZT values in the middle and high temperature range, with the highest value of 1.04 at 873 K.

POSSIBLE EVIDENCE FOR A VALENCE BAND SATELLITE IN PHOTOEMISSION SPECTRA FROM Sc(0001)

1994 ◽  
Vol 01 (04) ◽  
pp. 649-653 ◽  
Author(s):  
A.J. PATCHETT ◽  
S.S. DHESI ◽  
R.I.R. BLYTH ◽  
S.D. BARRETT
Keyword(s):  
Electronic Structure ◽  
Rare Earth ◽  
Binding Energy ◽  
Single Crystals ◽  
Valence Band ◽  
Ground State ◽  
Rare Earth Metals ◽  
Final State ◽  
Bulk Single Crystals ◽  
The Creation

An intense photoemission feature is observed at a binding energy of ~10 eV in the UV photoemission spectra from the (0001) surfaces of bulk single crystals of rare-earth metals. This emission cannot be explained in terms of ground state electronic structure and we have been unable to attribute its existence to the presence of contamination of the surface. We present some evidence that may indicate its origin lies in the creation, by the photoemission process, of a metastable two-hole final state.

The Study of Charge Transport in Nanoscale DNA Structures

2010 ◽  
Vol 1280 ◽  
Author(s):  
G. Bart ◽  
M. R. Singh ◽  
M. Zinke-Allamang
Keyword(s):  
Electrical Conductivity ◽  
Density Of States ◽  
Variable Range Hopping ◽  
Band Tail ◽  
Phonon Interaction ◽  
Dna Structures ◽  
Electron Phonon Interaction ◽  
Electric Field Dependence ◽  
Exponential Density ◽  
Base Distance

AbstractWe have studied the variable range hopping (VRH) mechanism for polarons in DNA structures using an exponential density of states. Due to the electron-phonon interaction localized polarons are formed in the DNA helix. The unwinding of DNA increases molecular orbital overlap between bases while decreasing the base-to-base distance. These types of vibrations create phonons. We consider that DNA has a band tail which has an exponential density of states and we have calculated the temperature- and the electric field dependence of the conductivity. We compare our model with the experiments of the electrical conductivity of samples of double-stranded H5N1 genes of avian Influenza virus DNA. Our theory is able to explain their data.

Determination of Hydrogen Density of States in Amorphous Silicon Using Fractional Evolution Experiments

1997 ◽  
Vol 467 ◽  
Author(s):  
A. J. Franz ◽  
W. B. Jackson ◽  
J. L. Gland
Keyword(s):  
Amorphous Silicon ◽  
Density Of States ◽  
Silicon Film ◽  
Mean Field ◽  
Frequency Factor ◽  
Silicon Films ◽  
Hydrogen Density ◽  
Heating And Cooling ◽  
Novel Method

ABSTRACTHydrogen plays an important role in the electronic behavior, structure and stability of amorphous silicon films. Therefore, determination of the hydrogen density of states (DOS) and correlation of the hydrogen DOS with the electronic film properties are important research goals. We have developed a novel method for determination of hydrogen DOS in silicon films, based on fractional evolution experiments. Fractional evolution experiments are performed by subjecting a silicon film to a series of linear, alternating heating and cooling ramps, while monitoring the hydrogen evolution rate. The fractional evolution data can be analyzed using two complementary memods, the fixed frequency factor approach and Arrhenius analysis. Using a rigorous, mean-field evolution model, we demonstrate the applicability of the two approaches to obtaining the hydrogen DOS in silicon films. We further validate both methods by analyzing experimental fractional evolution data foran amorphous silicon carbide film. Both types of analysis yield a similar double peaked density of states for the a-Si:C:H:D film.

scholarly journals An Analytical Study on the Local Electronic Density of States of the Valence Bands in Amorphous Silicon Carbide

1998 ◽  
Vol 21 (3) ◽  
pp. 217-219 ◽  
Author(s):  
M. A. Grado-Caffaro ◽  
M. Grado-Caffaro
Keyword(s):  
Silicon Carbide ◽  
Amorphous Silicon ◽  
Valence Band ◽  
Density Of States ◽  
Analytical Study ◽  
Electronic Density ◽  
Amorphous Silicon Carbide ◽  
Electronic Density Of States ◽  
Valence Bands ◽  
Hybrid Orbitals

A formulation for the energy-averaged local valence band density of states of amorphous silicon carbide is derived. To this end,sp3-type hybrid orbitals are employed.

XPS, AES AND UPS INVESTIGATION OF SnO2/Si AND DFT-BASED THEORETICAL STUDY WITHIN THE mBJ-GGA SCHEME

2020 ◽  
pp. 2050048
Author(s):  
A. MOKADEM ◽  
M. BOUSLAMA ◽  
B. KHAROUBI ◽  
A. OUERDANE ◽  
R. KHENATA ◽  
...  
Keyword(s):  
Valence Band ◽  
Density Of States ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Electronic Distribution ◽  
Complementary Techniques ◽  
Uv Photoelectron Spectroscopy ◽  
Theoretical Results

We investigate the growth performance of tin oxide on the Si substrate, achieved by spray pyrolysis using the sensitive analysis techniques X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). These complementary techniques confirm the growth of homogeneous SnO2 thin films. We also study the electronic distribution of the valence band of SnO2 theoretically using density functional theory (DFT). The chemical and physical properties of the material depend on the electron structure varying as a function of energy. The density of states (DOS) is calculated using the modified Becke–Johnson-Generalized Gradient Approximation (mBJ-GGA) in order to identify the electronic orbitals and the importance of their contribution to the electronic structure of the valence band. Furthermore, we use the experimental technique UV Photoelectron Spectroscopy (UPS) for studying the electronic distribution within the valence band and for validating the theoretical results of the density of states of SnO2/Si.

Sign in / Sign up

Export Citation Format

Share Document