Determination of the Density of Gap States in a-Si:H from Studies of Semiconductor/Oxide Multilayer Films

1987 ◽  
Vol 95 ◽  
Author(s):  
R. B. Jones ◽  
G. Moddel
Keyword(s):  
Activation Energy ◽  
Energy Gap ◽  
Multilayer Films ◽  
Thermally Grown Oxide ◽  
Experimental Results ◽  
Band Bending ◽  
The Difference ◽  
Gap States ◽  
Hydrogenated Amorphous

AbstractA method for determining the density of states [N(E)] in the upper half of the energy gap in hydrogenated amorphous silicon (a-Si:H) is proposed and experimental results are simulated. The method involves the growth and measurement of the planar conductivity in multilayer films in which each layer is separated by a thermally grown oxide. Band-bending occurs at each interface throughout the film thickness. The conductivity parallel to the layers in the films is a function of the band-bending, which in turn depends on N(E), in the energy range through which the Fermi level is shifted. Computer simulations of the oxide-induced band-bending have been used to generate curves of the conductivity as a function of layer-thickness for various N(E). By matching experimental results with the simulation curves, the N(E) may be deduced. The simulations have also been used to show the difference between the bulk conductivity activation energy and effective activation energy which is measured in films influenced by a surface oxide.

Theory of Hydrogen Complexes in Si

1990 ◽  
Vol 209 ◽  
Author(s):  
S. B. Zhang ◽  
W. B. Jackson
Keyword(s):  
Binding Energy ◽  
Raman Spectra ◽  
Experimental Results ◽  
Lattice Expansion ◽  
Strained Si ◽  
Amorphous Si ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
And Diffusion ◽  
Strained Bonds

ABSTRACTThe predominance of Si-H bonding and the origin of {111} platelets in hydrogenated Si remain important unsolvedproblems in the study of H in Si.Recent theoretical and experimental results indicate that H predominately enters the Si network in pairs. A promising diatomic H configuration consists of a bond centered H closely associated with an antibonding centered H. In this work, we show that adjacent diatomic H pairs have a binding energy of 0.2 eV/2H. The binding originates from relaxation of strained Si-Si backbonds. Further clustering of the H pairs eliminates all strained bonds, forming a hydrogenated platelet oriented along the {111} plane. The binding energy of 3.95 eV/2H for the platelet is 0.15 eV lower than that for interstitial H2 molecules in c-Si. Lattice expansion makes the platelets energetically more competitivewith the lowest energy Si-H bonding confi gration at hydrogenated Si (111) surfaces. These higher level complexes explainthe formation of platelets, Raman spectra, and absence of gap states in hydrogenated c- Si as well as the clustered phaseseen in NMR and of H evolution and diffusion in hydrogenated amorphous Si.

Comparison and Analysis of Different Standards for Determining Dust Resistivity

2012 ◽  
Vol 508 ◽  
pp. 110-113 ◽  
Author(s):  
Xin Jin ◽  
Sheng Jun Zhong ◽  
Wei Ye Li
Keyword(s):  
Experimental Results ◽  
Test Results ◽  
Comparison And Analysis ◽  
Electrostatic Precipitators ◽  
The Difference ◽  
Test Result

Accurate measurement of dust resistivity is important practically for electrostatic prevention and design of electrostatic precipitators. The test result of dust resistivity depends on the standard used. There are three standards widely used for determination of dust resistivity: IEC 1241-2-2, BS 5958-1 and ASME PTC28 4.05. Experimental devices are designed and constructed according to these standards. The schematics of test principles and circuits of different standards are introduced. Experimental results show that dust resistivity values determined by different standards are quite different, and in some cases the difference is even in 1~2 orders of magnitude. The test results according to IEC standard are the highest, while the results using ASME standard are the lowest. The methods given by IEC standard and BS standard are normally used in electrostatic prevention, while method given by ASME standard is applied to the design of electrostatic precipitators. It is necessary to choose the appropriate standard according to the application of dust resistivity.

Analytical determination of the density-of-gap-states distribution in amorphous semiconductors: Experimental results

1987 ◽  
Vol 35 (2) ◽  
pp. 614-618 ◽  
Author(s):  
V. Augelli ◽  
V. Berardi ◽  
R. Murri ◽  
L. Schiavulli ◽  
M. Leo ◽  
...  
Keyword(s):  
Amorphous Semiconductors ◽  
Experimental Results ◽  
Analytical Determination ◽  
Gap States

scholarly journals D-9 Determination of Activation Energy in Textured Metal-Metal Multilayer Films Via 2D XRD

2008 ◽  
Vol 23 (2) ◽  
pp. 174-174
Author(s):  
M. A. Rodriguez ◽  
D. P. Adams ◽  
R. G. Tissot
Keyword(s):  
Activation Energy ◽  
Multilayer Films ◽  
Metal Metal

Undoped Amorphous Silicon TFTs with n-Channel OR p-Channel Device Operation for the Determination of the Gap States Distribution.

1987 ◽  
Vol 95 ◽  
Author(s):  
Ruud E.I. Schropp ◽  
Jan F. Verwey
Keyword(s):  
Amorphous Silicon ◽  
Silicon Thin Film ◽  
Current Decay ◽  
Implantation Techniques ◽  
Integrated Logic ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Device Operation ◽  
Continuous Accumulation

AbstractHydrogenated amorphous silicon thin-film transistors (TFTs) were made with either n-channel or p-channel device operation. Layers of undoped amorphous silicon were deposited in the same run and appropriate contact implantation techniques were used. These devices offer the possibility of investigating unipolar conduction of either electrons or holes. In this way ambiguities in the field-effect (FE) analysis of the density of states (DOS) can be avoided. We present the DOS distribution over the entire band gap region of undoped amorphous silicon deduced from a pair of transfer characteristics (one forward and one in reverse). Both types of TFTs are subject to degradation under continuous accumulation conditions. The rate of current decay under hole accumulation appears to be larger than under electron accumulation, as is expected from the width of the respective tail-states distributions. The ON/OFF current ratios obtained for the p- and n-channel devices were 105 and 107, respectively, and both devices showed good pinchoff behaviour. Therefore, these devices are in principle attractive for application in novel amorphous silicon integrated logic circuits (IC).

Experimental and Numerical Investigations of TBC Behaviour after Aging, Subjected to Tension and Bending

2014 ◽  
Vol 216 ◽  
pp. 128-133 ◽  
Author(s):  
Tomasz Sadowski ◽  
Przemysław Golewski
Keyword(s):  
Numerical Model ◽  
Damage Model ◽  
Thermally Grown Oxide ◽  
Experimental Results ◽  
Thermal Barrier ◽  
Aircraft Engines ◽  
Combustion Chambers ◽  
Numerical Investigations ◽  
And Performance

Thermal Barrier Coatings (TBCs) have been extensively used in aircraft engines to improve durability and performance. They protect critical engine parts such as blades and combustion chambers, which are exposed to high temperatures and corrosive environment.Testing of coated metallic alloys, subjected to ageing process, allows determination of the TBCs properties. In this paper we performed 2 tests: uniaxial tension and bending. The aging of samples was carried out in 1000°C for times: 48h, 89h, 185h and 353h. Thermally Grown Oxide (TGO) layer thickness (SEM observations) and the strain level corresponding to damage of the TBCs were determined experimentally.The experimental results were used to build numerical model in Abaqus program. Brittle cracking damage model was applied to describe of the TBC layer degradation. Surface based cohesive behavior was used to model delamination of the interface between a bond coat (BC) and a top coat (TC).The proposed numerical model describes with high accuracy experimental results.

Measurement of Two Deep H Bonding Levels in Device Quality Glow Discharge a-SI:H

1995 ◽  
Vol 377 ◽  
Author(s):  
A. H. Mahan ◽  
E. J. Johnson ◽  
R. S. Crandall ◽  
H. M. Branz
Keyword(s):  
Activation Energy ◽  
Glow Discharge ◽  
Slow Component ◽  
Hydrogenated Amorphous Silicon ◽  
Diffusion Constant ◽  
Fast Process ◽  
Loss Process ◽  
Rate Processes ◽  
Hydrogenated Amorphous

ABSTRACTWe present the results of H effusion studies on device-quality glow discharge deposited hydrogenated amorphous silicon (a-Si:H) films. We measure the decrease in the amount of Si-H infrared absorption as pieces of an a-Si:H sample are annealed isothermally at temperatures from 425°C to 500°C, until more than 95% of the initial H is evolved. We use the rate equation for loss of H due to annealing to calculate the activation energy for H effusion. For anneals below 500°C we observe two distinct rate processes, a fast process corresponding to release of ∼ 70% of the total H (∼10 at. %) contained in the sample, and a slower process corresponding to effusion of the remainder. The fast loss process yields an activation energy of ∼1.4 eV; this is the energy level widely observed in diffusion coefficient measurements. A similar analysis for the slow loss process yields an activation energy of ∼2.1 eV and a diffusion constant prefactor higher than that for the fast loss process. We suggest that this slow component represents the first determination of the energy depth of the “isolated” H component commonly observed in nuclear magnetic resonance experiments.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

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