Metastable Defect Studies in Hydrogen Modulated Multilayer Amorphous Silicon

1994 ◽  
Vol 336 ◽  
Author(s):  
Daewon Kwon ◽  
J. David Cohen
Keyword(s):  
Defect Density ◽  
Metastable States ◽  
Gas Mixture ◽  
Defect Level ◽  
Initial State ◽  
Homogeneous Sample ◽  
Multilayer Sample ◽  
Local Properties ◽  
Short Time ◽  
Metastable Defect

ABSTRACTJunction capacitance methods were employed to investigate the metastable states in a-Si:H with hydrogen modulated Multilayer sample as well as companion homogeneous samples. Each layer in the multilayer sample was grown from the same gas mixture (SiH4+Ar or SiH4+H2) as that of homogeneous samples. We observed that in state A and metastable states produced by a short time light soaking the defect density of each layer in the multilayer sample track well the defect density of the corresponding homogeneous sample. This implies that “local” aspects of metastable defect creation dominate in the earlier light soaked states, and also the stable defects in state A are due to local properties of each layer as introduced during growth. However, for longer time light soaked states and succeeding partial annealed states the defect level of the multilayer sample is higher than either of homogeneous samples. However, the spatial variations of the stable defects are finally recovered when the sample is annealed at the same temperature as the initial state A.

Light-Induced Metastable Defects or Light-Induced Metastable H Atoms in a-Si:H Films?

1997 ◽  
Vol 467 ◽  
Author(s):  
C. Godet
Keyword(s):  
Experimental Data ◽  
Characteristic Time ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Exponential Time ◽  
Mobile Species ◽  
Hydrogenated Amorphous ◽  
Two Parameter ◽  
Metastable Defect ◽  
Trapping Sites

ABSTRACTIn hydrogenated amorphous silicon (a-Si:H) films, the increase of the metastable defect density under high-intensity illumination is usually described by an empirical two-parameter stretched-exponential time dependence (characteristic time τSE and dispersion parameter β). In this study, a clearly different (one-parameter) analytic function is obtained from a microscopic model based on the formation of metastable H (MSH) atoms in a-Si:H films. Assuming that MSH atoms are the only mobile species, only three chemical reactions are significant : MSH are produced from doubly hydrogenated (SiH HSi) configurations and trapped either at broken bonds or Si-H bonds, corresponding respectively to light-induced annealing (LIA) and light-induced creation (LIC) of defects. Competition between trapping sites results in a saturation of N(t) at a steady-state value Nss. A one-parameter fit of this analytical function to experimental data is generally good, indicating that the use of a statistical distribution of trap energies is not necessary.

Comparison of Current and Light Induced Defects in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
R.A. Street ◽  
W.B. Jackson ◽  
M. Hack
Keyword(s):  
Numerical Modelling ◽  
Reverse Bias ◽  
Defect Density ◽  
Reverse Current ◽  
Bias Current ◽  
Spatial Profile ◽  
Forward Current ◽  
Defect Creation ◽  
Induced Defects ◽  
Metastable Defect

Metastable defect creation by illumination and by a forward current in p-i-n devices are compared using CPM and reverse current measurements of the defect density. The data show that the same defects are formed by the two mechanisms, but with different spatial profiles. Numerical modelling shows how the spatial profile influences the reverse bias current.

Non-Equilibrium Critical Relaxation of Heisenberg Ferromagnets with Long-Range Correlated Defects

2012 ◽  
Vol 190 ◽  
pp. 39-42
Author(s):  
M. Medvedeva ◽  
Pavel V. Prudnikov
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Critical Behavior ◽  
Critical Exponents ◽  
Heisenberg Model ◽  
Three Dimensional ◽  
Initial State ◽  
Short Time ◽  
Theoretic Description ◽  
Good Agreement

The dynamic critical behavior of the three-dimensional Heisenberg model with longrangecorrelated disorder was studied by using short-time Monte Carlo simulations at criticality.The static and dynamic critical exponents are determined. The simulation was performed fromordered initial state. The obtained values of the exponents are in a good agreement with resultsof the field-theoretic description of the critical behavior of this model in the two-loopapproximation.

Regulation of ketone body flux in septic patients

1989 ◽  
Vol 257 (5) ◽  
pp. E665-E674 ◽  
Author(s):  
M. Beylot ◽  
M. Guiraud ◽  
G. Grau ◽  
P. Bouletreau
Keyword(s):  
Amino Acids ◽  
Fatty Acids ◽  
Parenteral Nutrition ◽  
Intravenous Infusion ◽  
Ketone Body ◽  
Normal Subjects ◽  
Initial State ◽  
Appearance Rate ◽  
Mild Hyperglycemia ◽  
Short Time

To assess the effect of sepsis on ketone body (KB) kinetics in humans, we measured in normal and septic subjects KB appearance rate (Ra) before (initial state) and during a rise of free fatty acids (FFA) level (intravenous infusion of a triglycerides emulsion). We studied normal subjects in postabsorptive state and septic patients when receiving an hypocaloric intravenous infusion of glucose and amino acids or 12 h after its interruption. When receiving glucose and amino acids infusion, septic patients had higher glucose and insulin levels than normal subjects, and despite lower FFA concentrations (255 +/- 44 vs. 480 +/- 51 mumol/l, P less than 0.05) comparable initial KB Ra (2.50 +/- 0.10 vs. 2.48 +/- 0.30 mumol.kg-1.min-1). Triglyceride infusion increased FFA to comparable values (septic 780 +/- 130, normal 730 +/- 45 mumol/l), but KB Ra rose in septic patients only to 3.7 +/- 1.1 instead of 7.7 +/- 1.1 mumol.kg-1.min-1 as in normal subjects (P less than 0.05). Somatostatin infusion decreased the hyperinsulinemia of septic patients but did not restore a normal ketogenesis. After interruption of nutriment infusion, septic patients had normal FFA levels and only mild hyperglycemia and hyperinsulinemia. Their initial KB Ra was not modified. However, their response of KB Ra (increase to 6.27 +/- 2.0 mumol.kg-1.min-1) to raised FFA levels (842 +/- 170 mumol/l) was comparable to the response of normal subjects. In conclusion, although septic patients receiving an hypocaloric parenteral nutrition had a depressed ketogenesis they were able to restore a normal ketogenic capacity after a short-time caloric deprivation. Glucose and/or insulin appears to have a major role in this modulation of hepatic ketogenesis.

Saturation of Metastable-Defect Density in a-Si:H

1990 ◽  
Vol 192 ◽  
Author(s):  
David Redfield ◽  
Richard H. Bube
Keyword(s):  
Steady State ◽  
Defect Density ◽  
Atomic Model ◽  
Transient Responses ◽  
Induced Defects ◽  
Metastable Defect

ABSTRACTThe existence of saturation (or steady state) in the density of light-induced defects in amorphous Si:H is shown to have major importance for the interpretation of the nature and origin of these defects. First, a number of characteristics of the steady-state and transient responses to light and temperature are described and contrasted. These lead to the conclusion that the saturation value is the only useful criterion of the number of defects in these materials. We then describe a new atomic model for defects, unifying both dopant-induced and light-induced defects. This model invokes foreign atoms in defects, and saturation reflects the limitation imposed by the numbers of such atoms. Many other observed properties of defects are explained by this model.

scholarly journals Laser deposition of iron in oxygen atmosphere

2011 ◽  
Vol 1 (1) ◽  
pp. 429-433
Author(s):  
Y. Yamada ◽  
A. Ito ◽  
K. Kuono ◽  
H. Yoshida ◽  
Y. Kobayashi
Keyword(s):  
Iron Oxide ◽  
Defect Density ◽  
Lattice Defect ◽  
Oxygen Atmosphere ◽  
Trivalent Iron ◽  
Laser Deposition ◽  
Gas Mixture ◽  
Iron Oxide Particles ◽  
Oxide Particles ◽  
Ar Gas

AbstractIron oxide films were produced by pulsed laser deposition (PLD) of 57Fe metal in an oxygen atmosphere and their compositions were studied by Mössbauer spectroscopy. The effects of gas-phase reactions were investigated by varying the pressure of O2 gas or an O2/Ar gas mixture. When PLD was performed in a high-pressure O2 atmosphere, the main product in the film was trivalent iron oxide particles. When the O2 pressure was reduced, hematite Fe2O3 became dominant in the film, while wüstite FeO was produced at very low O2 pressures. PLD in an O2/Ar gas mixture produced films of trivalent iron oxide particles and hematite solid, but wüstite was not produced. Increasing the substrate temperature during deposition induced annealing of the films, reducing the lattice defect density. X-ray diffraction patterns were obtained to confirm the assignments, and the surface morphologies of the films were investigated by scanning electron microscopy.

A similarity problem of a porous material drying

2008 ◽  
Vol 6 ◽  
pp. 75-81
Author(s):  
D.Ye. Igoshin
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Gas Mixture ◽  
Dimensional Problem ◽  
Vapor Mixture ◽  
Initial State ◽  
One Dimensional ◽  
Similarity Problem ◽  
Self Similar ◽  
Similar Solutions

The plano-one-dimensional problem of heat and mass transfer is considered when a porous semi-infinite material layer dries. At the boundary, which is permeable for the gas-vapor mixture, the temperature and composition of the gas are kept constant. Self-similar solutions are set describing the propagation of the temperature field and the moisture content field arising when heat is supplied. The intensity of dry flows is studied, depending on the initial state of the wet-porous medium, as well as the temperature and concentration composition of the vapor-gas mixture at the boundary of the porous medium.

Metastable states and defect density waves in modulated ferroelectrics

2018 ◽  
Vol 91 (8) ◽  
pp. 785-792
Author(s):  
Karsten Behrendt ◽  
Götz Eckold
Keyword(s):  
Defect Density ◽  
Metastable States ◽  
Density Waves

scholarly journals Sensitivity of CO oxidation toward metal oxidation state in ceria-supported catalysts: an operando DRIFTS-MS study

2016 ◽  
Vol 6 (3) ◽  
pp. 818-828 ◽  
Author(s):  
Andre Kaftan ◽  
Fabian Kollhoff ◽  
Thanh-Son Nguyen ◽  
Laurent Piccolo ◽  
Mathias Laurin ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation State ◽  
Supported Catalysts ◽  
The State ◽  
Gas Mixture ◽  
Metal Oxidation ◽  
Initial State ◽  
Oxygen Coverage ◽  
Catalyst Powder

CeO2 and Rh/CeO2 show CO to CO2 conversion according to the input gas mixture, independent of the state of the catalyst powder. Pt/CeO2 demonstrates additional dependence on the initial state of the catalyst (oxygen coverage/oxidation state).

Investigation of the Promotion Effect of Germane in Low Temperature Uhv-Cvd Silicon

1987 ◽  
Vol 102 ◽  
Author(s):  
Kevin J. Uram ◽  
Bernard S. Meyerson
Keyword(s):  
Low Temperature ◽  
Silicon Germanium ◽  
Crystalline Silicon ◽  
Defect Density ◽  
Single Crystal Silicon ◽  
Gas Mixture ◽  
Crystal Silicon ◽  
Germanium Silicon ◽  
Kinetics Of ◽  
Silicon Germanium Alloys

ABSTRACTHigh quality, low defect density, single crystalline silicon/germanium alloys have been grown on Si(100) substrate wafers in a low temperature UHV-CVD reactor. Using a silane/germane gaseous source, the growth rate of the epitaxial layer increases from 4 angstroms/minute with no germane present to 82 angstroms/minute with 12.7% germane present in the reaction gas mixture at 550C. The germanium/silicon ratio in the deposited alloy is a factor of two greater than the germane/silane ratio in the reaction gas mixture. The kinetics of this effect are studied and correlation to UHV hydrogen thermal desorption from single crystal silicon-germanium alloys are made.

Sign in / Sign up

Export Citation Format

Share Document