Temperature Dependence of the Photoinduced Degradation and Annealing in a-Si:H

2000 ◽  
Vol 609 ◽  
Author(s):  
Niko Schultz ◽  
P. Craig Taylor
Keyword(s):  
Temperature Dependence ◽  
Room Temperature ◽  
Dangling Bond ◽  
Defect States ◽  
Slow Increase ◽  
Spin Resonance ◽  
The Difference ◽  
Kinetics Of ◽  
Defect Densities ◽  
Spin Densities

ABSTRACTWe investigated the temperature dependence of the production and annealing kinetics of the light induced defect states in a:Si:H by electron spin resonance (ESR). At low temperatures (T ∼ 25 K) the silicon dangling bond production is about half as efficient as it is at 300 K. Defects, which are created below about 100 K, almost entirely anneal at room temperature. A sample of a-Si:H, which is subjected to several photo-excitation and annealing cycles, shows a very slow increase of both the degraded and annealed defect densities. The difference in the spin densities between the annealed and degraded states decreases with an increasing number of degradation/annealing cycles.

Evolution of D0 and non-D0 Light Induced Defect States in a-Si:H Materials and Their Respective Contribution to Carrier Recombination

2004 ◽  
Vol 808 ◽  
Author(s):  
J. M. Pearce ◽  
J. Deng ◽  
V. Vlahos ◽  
R. W. Collins ◽  
C. R. Wronski ◽  
...  
Keyword(s):  
Room Temperature ◽  
Defect States ◽  
Carrier Recombination ◽  
Spin Resonance ◽  
Respective Contribution ◽  
Gap States ◽  
Induced Changes ◽  
Induced Defects ◽  
Kinetics Of ◽  
Absorption Measurements

A study has been carried out on the evolution of light induced defects in protocrystalline (diluted) a-Si:H films under 1 sun illumination. A room temperature reversal is observed in the photocurrents at 25°C, which is consistent with the relaxation in the recombination currents on corresponding p-i-n solar cells. It is also consistent with the pressure of “fast” states such as have been observed after high intensity illumination. Even with the limitations imposed by the relaxation in the light induced changes on the subgap absorption measurements, the evolution of distinctly different gap states centered around 0.9 and 1.15eV from the conduction band was identified. The kinetics of the electron occupied states, kN(E), at these two energies is compared with that of the neutral dangling bond (D0) densities as measured with electron spin resonance. Because of the similarity between the preliminary results of these kinetics it has not been possible to identify which states correspond to the D0 nor to draw any reliable conclusions about the nature of the different states.

Charged Defect State Distributions Obtained from the Analysis of Photoconductivities in Intrinsic a-Si:H Films

1994 ◽  
Vol 336 ◽  
Author(s):  
Mehmet Güneş ◽  
R. W. Collins ◽  
C. R. Wronski
Keyword(s):  
Charged Defect ◽  
Defect States ◽  
State Distribution ◽  
Spin Resonance ◽  
Neutral Defect ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Defect Densities ◽  
Positively Charged ◽  
Spin Densities

ABSTRACTSteady-state photoconductivity, sub-bandgap absorption and electron spin resonance (ESR) Measurements were carried out on annealed and light soaked intrinsic hydrogenated Amorphous silicon (a-Si:H) films. The experimental results were modeled using detailed numerical Model. The defect densities derived from the sub-bandgap absorption in the light soaked films were correlated with the ESR spin densities. Selfconsistent fitting of the data was obtained using a gap state distribution which consists of positively charged defect states above, negatively charged defect states below and neutral defect states at about Midgap. Both the annealed and the light degraded states are modeled using the same distribution of gap states whose densities increase upon light soaking with a slight increase in the ratio of the neutral to charged defect densities. These results on intrinsic a-Si:H are consistent with those of charged defect Models.

Temperature Dependence of the Decay of Optically Excited Charge Carriers in Amorphous Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
J. Whitaker ◽  
P. C. Taylor
Keyword(s):  
Temperature Dependence ◽  
Amorphous Silicon ◽  
State Density ◽  
Charge Carriers ◽  
Band Tail ◽  
Spin Resonance ◽  
Recombination Processes ◽  
Long Time ◽  
Tail Structure ◽  
Kinetics Of

AbstractWe report the temperature dependence of the growth and decay of the optically induced electron spin resonance (LESR) on short and long time scales (10-3 s < t < 2500 s). This range of times spans the region between previously published photoluminescence and the LESR data. In addition, we examine the steady-state density of optically excited charge carriers as a function of temperature. These measurements lead to a better understanding of the band tail structure of amorphous silicon as well as the kinetics of the excitation and recombination processes.

Radiation damage in polyethylene as studied by electron spin resonance

1961 ◽  
Vol 262 (1309) ◽  
pp. 207-218 ◽  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Alkyl Radical ◽  
Room Temperature ◽  
Chemical Properties ◽  
Resonance Method ◽  
Alkyl Radicals ◽  
Spin Resonance ◽  
Physical And Chemical ◽  
Kinetics Of

The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable un­identified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.

ESR study of activated carbon fibers: preliminary results

1993 ◽  
Vol 8 (9) ◽  
pp. 2282-2287 ◽  
Author(s):  
S.L. di Vittorio ◽  
A. Nakayama ◽  
T. Enoki ◽  
M.S. Dresselhaus ◽  
M. Endo ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Carbon Fibers ◽  
Room Temperature ◽  
Broad Peak ◽  
Activated Carbon Fibers ◽  
Temperature Peak ◽  
Dangling Bond ◽  
Surface Areas ◽  
Spin Resonance

We have carried out Electron Spin Resonance (ESR) measurements on activated carbon fibers (ACF) with specific surface areas (SSA) of 3000 and 2000 m2/g. The ESR spectrum of ACF fibers in air is extremely broad (500 to 1000 Gauss), and the spin susceptibility decreases rapidly with decreasing specific surface area. Also measured was the ESR signal of the desorbed fibers in vacuum. As a result of desorption, the broad peak decreases slightly in intensity, and a narrow (≍65 Gauss at room temperature) peak appears. We report results on the temperature dependence of both peaks. The narrow peak is interpreted as due to spins associated with dangling bonds, whereas we attribute the broad peak to the conduction carrier spins which is broadened by the boundary scattering process (T1 contribution) and the dipolar broadening process (T2 contribution) associated with the dangling bond spins.

Transport Studies in Single-Crystal Films of Cosi2 and Nisi2

1983 ◽  
Vol 25 ◽  
Author(s):  
J. C. Hensel ◽  
R. T. Tung ◽  
J. M. Poate ◽  
F. C. Unterwald ◽  
D. C. Jacobson
Keyword(s):  
Thin Films ◽  
Single Crystal ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Transport Studies ◽  
Single Crystal Films ◽  
Crystal Films ◽  
The Difference ◽  
Temperature Resistivity

ABSTRACTTransport studies have been performed on thin films of CoSi 2 and NiSis2 in the temperature range 1 to 300 K. The conductivities are metallic with essentially the same temperature dependence; however, the residual resistivities are markedly different even though the two silicides are structurally similar (the room temperature resistivity of NiSi2 being at least twice that of CoSi2 of 15 μΩ cm). The difference is attributed to intrinsic defects in NiSi2. This defect has been simulated by ion bombardment of the film where it is also shown that Matthiesen's rule is obeyed over a remarkable range of bombardment doses.

scholarly journals Транспортные процессы с участием атомов углерода между поверхностью и объемом родия при образовании и разрушении графена

2020 ◽  
Vol 54 (6) ◽  
pp. 552
Author(s):  
Е.В. Рутьков ◽  
Е.Ю. Афанасьева ◽  
Н.Р. Галль
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Temperature Dependence ◽  
Atomic Carbon ◽  
Graphene Growth ◽  
Carbon Dissolution ◽  
The Difference ◽  
Kinetics Of

Equilibrium transport of atomic carbon between Rh surface and bulk has been studied. This transport controls the kinetics of the phase transition resulting in graphene growth or destruction. The difference ΔE=0.7 eV has been measured between the activation energy of atomic carbon dissolution E1s and that of its segregation from the bulk to the surface E1s. The temperature dependence of chemisorbed carbon critical cover Neq = Neq(T) has been measured, that is the cover when 2D phase transition takes place and graphene islands start to grow. E.g., Neq = 7.7•1014 cm-2 at T = 1800 K, and Neq = 3.1•1014 cm-2 at T = 1000 K.

A Comparative Study of Defect States in Light-Soaked and High-Temperature-Annealed a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
Z. M. Saleh ◽  
H. Tarui ◽  
S. Tsuda ◽  
S. Nakano ◽  
Y. Kuwano
Keyword(s):  
High Temperature ◽  
Light Exposure ◽  
Dark Conductivity ◽  
Defect States ◽  
Narrow Component ◽  
Spin Resonance ◽  
The Difference ◽  
Increasing Temperature ◽  
Induced Changes ◽  
Induced Defects

Our previous results of light-induced electron spin resonance (LESR) indicate that, in hydrogenated amorphous silicon (a-Si:H), light-induced defects differ from those formed during deposition or high-temperature annealing. A plausible interpretation, in which light-induced defects occupy higher-energy states, was proposed to explain these differences. In this study, the constant photocurrent method (CPM), dark conductivity and steady-state (SS) LESR are used to supply new evidence for the difference and conduct two important tests on our hypothesis. In striking agreement with our predictions, we find that the light-induced changes in the SS-LESR lineshape (a decrease in the narrow component relative to the broad one upon light exposure) become indeed more dramatic as the demarcation energies move closer to the midgap by increasing temperature or decreasing bias-light intensity for SS-LESR.

Hydrogen Collision Model of The Staebler-Wronski Effect: Microscopics and Kinetics

1998 ◽  
Vol 507 ◽  
Author(s):  
Howard M. Branz
Keyword(s):  
Room Temperature ◽  
Pair Creation ◽  
Hole Pair ◽  
Dangling Bond ◽  
Electron Hole ◽  
Spin Resonance ◽  
Electron Hole Pair ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous ◽  
Creation Rate

ABSTRACTA new microscopic and kinetic model of light-induced metastability in hydrogenated amorphous silicon (a-Si:H) is described. Recombination and trapping of photoinduced carriers excite hydrogen from deep Si-H bonds into a mobile configuration, leaving a dangling bond (DB) defect at the site of excitation. Normally, mobile H are recaptured at DB defects and no metastability or net DB production results. However, when two mobile H collide, they form a metastable two-hydrogen complex and leave two spatially-uncorrelated Staebler-Wronski DBs. Thermal and light-induced annealing occur when mobile H are excited from the metastable two-H complex; they diffuse and are recaptured to DBs. The microscopic model is entirely compatible with electron-spin-resonance results showing neither DB-DB nor DB-H spatial correlation of the light-induced DBs. The model leads to new differential equations describing the evolution of the mobile H and DB densities. These equation equations explain the observed room-temperature Ndb∼G2/3t1/3 dependence of DB creation upon the electron-hole pair creation rate (G) and time. The model also accounts for both t1/3-kinetics at 4.2K and t1/2-kinetics under laser-pulse soaking. Neither of these results can be explained within the prevailing electron-hole pair recombination model.

The kinetics of E-selectin- and P-selectin-induced intermediate activation of integrin αLβ2 on neutrophils

2021 ◽  
Vol 134 (18) ◽  
Author(s):  
Fangyuan Zhou ◽  
Fang Zhang ◽  
Veronika I. Zarnitsyna ◽  
Larissa Doudy ◽  
Zhou Yuan ◽  
...  
Keyword(s):  
Room Temperature ◽  
Intercellular Adhesion Molecule ◽  
Intercellular Adhesion Molecule 1 ◽  
Slow Increase ◽  
Rolling Velocity ◽  
Dependent Change ◽  
Temperature Activation ◽  
Selectin Binding ◽  
Kinetics Of ◽  
Dose Dependent

ABSTRACT Selectins and integrins are key players in the adhesion and signaling cascade that recruits leukocytes to inflamed tissues. Selectin binding induces β2 integrin binding to slow leukocyte rolling. Here, a micropipette was used to characterize neutrophil adhesion to E-selectin and intercellular adhesion molecule-1 (ICAM-1) at room temperature. The time-dependent adhesion frequency displayed two-stage kinetics, with an E-selectin-mediated fast increase to a low plateau followed by a slow increase to a high plateau mediated by intermediate-affinity binding of integrin αLβ2 to ICAM-1. The αLβ2 activation required more than 5 s contact to E-selectin and spleen tyrosine kinase (Syk) activity. A multi-zone channel was used to analyze αLβ2 activation by P-selectin in separate zones of receptors or antibodies, finding an inverse relationship between the rolling velocity on ICAM-1 and P-selectin dose, and a P-selectin dose-dependent change from bent to extended conformations with a closed headpiece that was faster at 37°C than at room temperature. Activation of αLβ2 exhibited different levels of cooperativity and persistent times depending on the strength and duration of selectin stimulation. These results define the precise timing and kinetics of intermediate activation of αLβ2 by E- and P-selectins.

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