Metastability Under High-Intensity Light of Device-Quality He-Diluted, H2-Diluted and Standard a-Si:H Films Deposited Between 50°C and 350°C

1994 ◽  
Vol 336 ◽  
Author(s):  
P. Morin ◽  
P. Roca i Cabarrocas
Keyword(s):  
High Intensity ◽  
Defect Density ◽  
Red Light ◽  
Rf Power ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Kinetics Of ◽  
Defect Densities ◽  
High Intensity Light

ABSTRACTWe report the results of a study of the metastability under illumination by high intensity red light of device quality a-Si:H thin films deposited using a wide range of deposition conditions. The process variables included substrate temperature, pressure, rf power, and dilution of silane by He or H2. In-situ Monitoring of the sample conductivity and defect density during light-soaking provides the kinetics of the degradation of the electronic properties of the films. We observe equilibration of the photoconductivity and of the defect density. The characteristic time of equilibration τse of the defect density varies by more than an order of magnitude, dividing the samples into two groups: one group with a τse on the order of 103 seconds, the other with a τse on the order of 104 seconds. Low steady state defect densities combined with high ημτ products are observed for “standard” a-Si:H deposited between 100°C and 250°C and He-diluted films deposited above 250°C.

Defect Equilibration in Amorphous Silicon Films Submitted to High Intensity Illumination

1996 ◽  
Vol 420 ◽  
Author(s):  
C. Godet ◽  
P. Roca i Cabarrocas
Keyword(s):  
High Intensity ◽  
Urbach Energy ◽  
Defect Density ◽  
Fast Kinetics ◽  
Slow Kinetics ◽  
Wide Range ◽  
Medium Range ◽  
Infrared Signature ◽  
Kinetics Of ◽  
Creation Rate

AbstractIn plasma-deposited a-Si:H films, the increase of the metastable defect density produced by high-intensity illumination usually follows a stretched-exponential time-dependence, with a characteristic time τSE and a steady-state value Nss. For a wide range of deposition conditions, we have observed that both parameters depend on the material properties. The strong correlation between Nss and the monohydride [SiH]2000 density, reported previously, has been interpreted as due to the trapping of metastable H atoms at specific sites.In this study of the kinetics of defect equilibration under high-intensity illumination, we find two groups of a-Si:H films with fast and slow kinetics, respectively. These two groups display a very different dependence of the defect creation rate as a function of the optical gap. For the fast kinetics films, we emphasize the critical influence of the Urbach energy Eu deduced from the exponential optical absorption edge (1/τSE increases as a function of Eu). The slow kinetics films are characterized by a high nanovoid density evidenced by their SiHx infrared signature at 2090 cm-1. The results are discussed in relation to the medium-range H motion.

scholarly journals Anthocyanin Production Using Rough Bluegrass Treated with High-Intensity Light

HortScience ◽  
2016 ◽  
Vol 51 (9) ◽  
pp. 1111-1120 ◽  
Author(s):  
Dominic P. Petrella ◽  
James D. Metzger ◽  
Joshua J. Blakeslee ◽  
Edward J. Nangle ◽  
David S. Gardner
Keyword(s):  
Blue Light ◽  
High Intensity ◽  
Red Light ◽  
Leaf Tissue ◽  
Anthocyanin Synthesis ◽  
Anthocyanin Content ◽  
Poa Trivialis ◽  
Total Light ◽  
Anthocyanin Production ◽  
High Intensity Light

Anthocyanins are plant pigments that are in demand for medicinal and industrial uses. However, anthocyanin production is limited due to the harvest potential of the species currently used as anthocyanin sources. Rough bluegrass (Poa trivialis L.) is a perennial turfgrass known for accumulating anthocyanins, and may have the potential to serve as a source of anthocyanins through artificial light treatments. The objectives of this research were to determine optimal light conditions that favor anthocyanin synthesis in rough bluegrass, and to determine the suitability of rough bluegrass as a source of anthocyanins. When exposed to high-intensity white light, rough bluegrass increased anthocyanin content by 100-fold on average, and anthocyanin contents greater than 0.2% of dry tissue weight were observed in some samples. Blue light, at intensities between 150 and 250 μmol·m−2·s−1, was the only wavelength that increased anthocyanin content. However, when red light was applied with blue light at 30% or 50% of the total light intensity, anthocyanin content was increased compared with blue light alone. Further experiments demonstrated that these results may be potentially due to a combination of photosynthetic and photoreceptor-mediated regulation. Rough bluegrass is an attractive anthocyanin production system, since leaf tissue can be harvested while preserving meristematic tissues that allow new leaves to rapidly grow; thereby allowing multiple harvests in a single growing season and greater anthocyanin yields.

scholarly journals In Situ Electrochemical Study of the Growth Kinetics of Passive Film on TC11 Alloy in Sulfate Solution at 300 °C/10 MPa

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1135 ◽  
Author(s):  
Lei Zha ◽  
Heping Li ◽  
Ning Wang
Keyword(s):  
Passive Film ◽  
Growth Kinetics ◽  
Electrochemical Behavior ◽  
Electrochemical Impedance ◽  
Sulfate Solution ◽  
Open Circuit ◽  
Hydrothermal Systems ◽  
Wide Range ◽  
Kinetics Of

TC11 alloy is a promising structural material, and has a wide range of applications in many corrosive and high temperature hydrothermal systems. The passive film has an important influence on its electrochemical behavior. In this study, in-situ electrochemical methods (that is, open circuit potential (OCP), linear polarization (LP) and electrochemical impedance spectroscopy (EIS)) were used to monitor the long period electrochemical behavior of TC11 alloy in 0.01 M Na2SO4 solution at 300 °C/10 MPa. The growth kinetics of the passive film was mainly studied. The correlation between the evolution of the electrochemical behavior and the growth of the oxide film was discussed. The results showed that although the OCP gradually stabilized after twenty thousand seconds, henceforth the polarization resistance (Rp) was still increasing due to the thickening of the passive film. An equivalent circuit was proposed to fit the EIS experimental data, leading to determination of film capacitance and film resistance. Besides, the electrochemical data was interpreted in terms of the point defect model (PDM). The EIS results are consistent with the Rp results.

Intensities in Raman spectra III. A photoelectric recording Raman spectrometer for intensity measurements

1956 ◽  
Vol 237 (1209) ◽  
pp. 186-196 ◽  
Keyword(s):  
Light Source ◽  
High Intensity ◽  
Room Temperature ◽  
Recording System ◽  
Photoelectric Recording ◽  
Intensity Measurements ◽  
Wide Range ◽  
Recording Potentiometer ◽  
Phase Sensitive ◽  
High Intensity Light

A description is given of a Raman apparatus designed primarily for intensity measurements by direct photo-electric recording. A special feature is a high- intensity light source with four Toronto-type mercury arcs. It is possible to use a variety of sample volumes and to make measurements on samples over a wide range of temperatures both above and below room temperature. Semi-quantitative polarization measurements can also be made. The recording system uses an E. M. I. eleven-stage photomultiplier cell with a. c. amplification at 285 c/s, followed by rectification in a phase-sensitive homodyne circuit. The output is fed to a Cambridge recording potentiometer. Details of calibration for intensity measurements are given and sample records are shown illustrating the various applications of the apparatus.

An Alternative Model for the Kinetics of Light-Induced Defects in A-Si:H

1991 ◽  
Vol 219 ◽  
Author(s):  
Paulo V. Santos ◽  
W. B. Jackson ◽  
R. A. Street
Keyword(s):  
Time Dependence ◽  
Valence Band ◽  
Defect Formation ◽  
Defect Density ◽  
Generation Rate ◽  
Band Tail ◽  
Defect Generation ◽  
Wide Range ◽  
Induced Defects ◽  
Kinetics Of

ABSTRACTThe kinetics of light-induced defect generation in a-Si:H was investigated over a wide range of illumination intensities and temperatures. The defect density around 1016cm-3 exhibits a power-law time dependence Ns ∼ G2εfε with ε = 0.2 to 0.3, where G is the photo-carrier generation rate. A model for the kinetics of defect generation is proposed based on the existence of an exponential distribution of defect formation energies in the amorphous network, associated with the valence band tail states. The model reproduces the observed time dependence of the defect density with an exponent e determined by the exponential width of the valence band tail. The temperature dependence of the defect generation rate is well-reproduced by the model, which provides a connection between the Stabler-Wronski effect and the weak-bond model.

Kinetics of Light-Induced Degradation of a-Si:H Solar Cells Compared to I-Layer Films

1992 ◽  
Vol 258 ◽  
Author(s):  
X.R. Li ◽  
S. Wagner ◽  
M. Bennett ◽  
S. Fonash
Keyword(s):  
Solar Cells ◽  
Defect Density ◽  
Monochromatic Light ◽  
Performance Parameters ◽  
Electron Hole ◽  
Different Temperatures ◽  
Electron Hole Pair ◽  
Pair Generation ◽  
Kinetics Of ◽  
High Intensity Light

ABSTRACTWe report the CPM defect density of a-Si:H material and the performance characteristics of pin solar cells during high-intensity light-soaking. In one group of experiments we compared the effects of soaking with monochromatic light from a Kr+ laser to white light from a Xe arc lamp. The effects are identical for the same electron-hole pair generation rate. In a second group of experiments we light-soaked at the two different temperatures of 50°C and 90°C. At 90°C the defect density saturates at a lower value than at 50°C, and correspondingly the cell performance parameters saturate at higher values.

Glues Make Gummy Metals Easy to Cut

2019 ◽  
Author(s):  
Anirudh Udupa ◽  
Tatsuya Sugihara ◽  
James B. Mann
Keyword(s):  
Plastic Deformation ◽  
Cutting Forces ◽  
Defect Density ◽  
Deformation Mode ◽  
Flow Mode ◽  
Force Measurements ◽  
Low Friction ◽  
Machining Processes ◽  
Order Of Magnitude

Abstract Metals such as Cu, Al, Ni, Ta and stainless steels, despite their softness and ductility, are considered difficult to machine. This is due to large cutting forces and corresponding formation of a very thick chip during cutting and hence these metals are referred to as “gummy”. Their poor machinability of these materials arises because of an unsteady and highly redundant mode of plastic deformation referred to as sinuous flow. The prevailing plastic deformation mode during machining can be overcome by the application of certain coatings and chemical media on the un-deformed free surface of the workpiece ahead of the cutting process. Using in-situ imaging and concurrent force measurements we present two different mechanochemical routes through which these media can improve machinability. The first route, which requires chemicals that adhere to the metal surface, such as glues and inks, improves cutting by inducing a change in the local plastic deformation mode — from sinuous flow to one characterized by periodic fracture or segmented flow. The second route, which requires chemicals that can react with the workpiece to form a low-friction layer, changes the sinuous flow mode to a smooth, laminar one. Both routes decrease cutting forces by more than 50% with order of magnitude improvement in surface texture as characterized by measured roughness and defect density. The results suggest a broad range of opportunities for improving performance of machining processes for many difficult-to-cut gummy metals.

Defect Reduction of Cvd-Grown Cubic SiC Epitaxial Films on Off-Axis Si(100) Substrates with a Novel Off-Direction.

1990 ◽  
Vol 198 ◽  
Author(s):  
Katsuki Furukawa ◽  
Yoshihisa Fujii ◽  
Akira Suzuki ◽  
Shigeo Nakajima
Keyword(s):  
Defect Density ◽  
Chemical Vapor ◽  
Epitaxial Films ◽  
Defect Reduction ◽  
Fault Density ◽  
Electrolytic Etching ◽  
Order Of Magnitude ◽  
First Time ◽  
Defect Densities ◽  
Sic Films

ABSTRACTMonocrystalline cubic SiC (β -SiC) thin films with lower defect densities have been epitaxially grown by chemical vapor deposition on off-axis Si (100) substrates with off-directions different from the conventional 〈011〉. Stacking faults of β -SiC films are investigated by the electrolytic etching and SEM observation. The effects of off-direction deviated from 〈011〉 are examined for the first time. The off-angle is fixed at 2 degrees. We find a reduction in defect density with increasing deviation angle θ, of off-direction from [011] toward [011[ (θ = 0 - 45°). The defect density becomes one order of magnitude smaller than that of on-axis (100) substrates. A typical value of the stacking fault density is approximately 6 × 106 cm−2 on the substrate with θ = 30° (film thickness: 24μ m).

Effect of C Impurities in a-Si:H as Measured by Drive-Level Capacitance, Photo Current, and Electron Spin Resonance

1993 ◽  
Vol 297 ◽  
Author(s):  
J. Hautala ◽  
T. Unold ◽  
J.D. Cohen
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Defect Density ◽  
Drive Level ◽  
Level Data ◽  
Definite Effect ◽  
Wide Range ◽  
Spin Resonance ◽  
Defect Densities ◽  
Photo Current

The effect of C impurities in a-Si:H in levels of 0.4 to 2.6 at. % were studied over a wide range of metastable defect densities. Three complimentary experimental techniques [electron spin resonance (ESR), drive-level capacitance (DLC) and photo-current] were employed to track the material's defect density with light soaking and annealing, as well as Urbach energies, midgap absorption and mobility gaps energies as a function of the C content. Our results show C impurities have a definite effect on the initial and saturated defect densities, as well as the midgap absorption and Urbach energies at levels 1 at. % and above. The results indicate that C acts mainly as a center for increased disorder in the material which results in an increase in the bandtail widths, and consequently an increase in intrinsic defects. Comparison to the ESR and drive-level data show an excellent agreement between these two techniques in determining the bulk defect densities in a-Si:H.

KINETICS OF METABOLIC ACTIVATION IN CANINE MUSCLE IN SITU AT THE ONSET OF HIGH INTENSITY CONTRACTIONS

2001 ◽  
Vol 33 (5) ◽  
pp. S278
Author(s):  
K M. Kelley ◽  
R A. Howlett ◽  
L B. Gladden ◽  
B Grassi ◽  
M C. Hogan
Keyword(s):  
High Intensity ◽  
Metabolic Activation ◽  
Kinetics Of
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