Phototransport Properties of a-SiC:H Alloys

1995 ◽  
Vol 377 ◽  
Author(s):  
G. Nery ◽  
A. Ramirez ◽  
O. Resto ◽  
S. Z. Weisz ◽  
Y. Lubianiker ◽  
...  
Keyword(s):  
Light Intensity ◽  
Carbon Concentration ◽  
Charge Carriers ◽  
Recombination Center ◽  
Dangling Bonds

ABSTRACTWe report a study of the mobility-lifetime products of the two charge carriers in a-SiC:H alloys. The measurements were carried out as a function of the carbon concentration and the temperature. An analysis, relying on the interpretation of the corresponding light intensity exponents, indicates that neutral dangling bonds control the electrons' lifetime while another recombination center controls the holes' lifetime.

The Tail States as Sensitizing Recombination Centers for Holes Lifetime in a-Si:H

1998 ◽  
Vol 507 ◽  
Author(s):  
Y. Lubianiker ◽  
R. Rapaport ◽  
I. Balberg ◽  
L. Fonseca ◽  
S.Z. Weisz
Keyword(s):  
Light Intensity ◽  
Thermal Quenching ◽  
Charge Carriers ◽  
Numerical Calculations ◽  
Dangling Bonds ◽  
Intensity Dependence ◽  
Recombination Model ◽  
Light Intensities ◽  
Recombination Centers

ABSTRACTWe have measured the dependence of the holes mobility-lifetime product on temperature under various light intensities in intrinsic a-Si:H. We find that this product exhibits thermal quenching which is accompanied by a superlinear light intensity dependence. Numerical calculations that we have carried out show that these results can be accounted for within the framework of the conventional recombination model. However, to yield such an agreement the capture coefficients for both charge carriers at the tail states must be smaller than the corresponding coefficients for the dangling bonds. Thus the sensitizing nature of the tail states is revealed.

Mobility-Lifetime Products in Glow Discharge and RF Sputter Deposited A-Si:H

1994 ◽  
Vol 336 ◽  
Author(s):  
M. H. Farias ◽  
A. Roche ◽  
S. Z. Weisz ◽  
H. Jia ◽  
J. Shinar ◽  
...  
Keyword(s):  
Light Intensity ◽  
Glow Discharge ◽  
Comparative Study ◽  
Deposition Temperature ◽  
Charge Carriers ◽  
Dangling Bonds ◽  
Majority Carrier ◽  
Recombination Processes ◽  
Pool Model ◽  
Sputter Deposited

ABSTRACTA comparative study of the deposition temperature (Ts) dependence of the Mobility-lifetime (μτ) products of the charge carriers in glow-discharge and rf sputter-deposited a-Si:H is described and discussed. The Ts-dependence of the μτ's the majority carrier light-intensity exponents of the two types of films are strikingly similar. These observations lead to the conclusion that the structure of the recombination levels as well as the recombination processes are in accord with the “defect pool” Model, in contrast to previous suggestions. The differences between the two types of films thus appear to be limited to the differences in the concentrations of dangling bonds.

Theory of injection photovoltages in organic insulators

1976 ◽  
Vol 29 (10) ◽  
pp. 2123 ◽  
Author(s):  
JS Bonham
Keyword(s):  
Light Intensity ◽  
Surface States ◽  
Threshold Value ◽  
High Light Intensity ◽  
Open Circuit ◽  
Charge Carriers ◽  
Single Carrier ◽  
Injection Mechanism ◽  
Wavelength Variation ◽  
Open Circuit Photovoltage

Development of an open-circuit photovoltage, U, in an organic insulator by photoinjection of charge carriers from the electrodes is treated theoretically. In the single-carrier case (both electrodes injecting the same carrier) it is shown that, in the absence of surface traps, U increases at a rate of 60 mV per decade of light intensity, II, above a threshold value of II. Photoinjection from the back (unilluminated) electrode by incompletely absorbed light causes U to become independent of ll at high light intensity. The same process may also cause U to change sign as the wavelength approaches an absorption minimum of the organic. Traps in the bulk of the insulator do not affect the single-carrier photovoltage, but traps at the surface may complicate the intensity dependence of U if they are involved in the injection mechanism. They may for example cause U to decrease and change sign at high n. Only shallow surface traps are considered. Possible effects of surface states are discussed briefly. The major assumption of this paper--neglect of all but injected charge carriers-breaks down in principle in the two-carrier case. However, if there are no sources of photovaltage in the bulk of the insulator the two-carrier case gives a stronger dependence of U on II, and no saturation or possibility of change of sign with wavelength variation. Predictions of the model are shown to agree with the results for a number of systems reported in the literature.

Light-Intensity Dependence of the Staebler-Wronski Effect in a-Si:H with Various Densities of Defects

2005 ◽  
Vol 862 ◽  
Author(s):  
Minoru Kumeda ◽  
Ryohei Sakai ◽  
Akiharu Morimoto ◽  
Tatsuo Shimizu
Keyword(s):  
Light Intensity ◽  
Weak Dependence ◽  
Rate Equations ◽  
Dangling Bonds ◽  
Illumination Time ◽  
Intensity Dependence ◽  
Weak Light ◽  
Staebler Wronski Effect

AbstractThe light-intensity dependence of the photocreation of dangling bonds (DBs) were investigated for a-Si:H films with increasing density of defects before light soaking. Samples in which the density of neutral DBs had been increased by annealing at 400 C for 1 h exhibited a weak light-intensity dependence of the photocreated DBs compared to that for the as-deposited sample. Furthermore, the sample which had been illuminated with a light intensity of 1 W/cm2 for 1 h also showed a weak dependence. The results can be qualitatively explained by using rate equations for the densities of DBs and floating bonds (FBs) based on the FB-mediated photocreation of DBs. When both the densities of DBs and FBs before illumination increase, the light-intensity dependence of the DB density for a moderate value of the illumination time becomes weaker, qualitatively consistent with the observed results.

Fine structure of the retina of the giant scallop, Placopecten magellanicus

1984 ◽  
Vol 42 ◽  
pp. 312-313
Author(s):  
C.V.L. Powell
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Intensity ◽  
Scanning Electron Microscope ◽  
Eye Development ◽  
Preliminary Observation ◽  
Columnar Epithelium ◽  
Placopecten Magellanicus ◽  
Environmental Light ◽  
Scanning Electron

The overall fine structure of the eye in Placopecten is similar to that of other scallops. The optic tentacle consists of an outer columnar epithelium which is modified into a pigmented iris and a cornea (Fig. 1). This capsule encloses the cellular lens, retina, reflecting argentea and the pigmented tapetum. The retina is divided into two parts (Fig. 2). The distal retina functions in the detection of movement and the proximal retina monitors environmental light intensity. The purpose of the present study is to describe the ultrastructure of the retina as a preliminary observation on eye development. This is also the first known presentation of scanning electron microscope studies of the eye of the scallop.

Effect of light intensity on the ultrastructure of the filamentous cyanobacterium, Anabaena variabilis

1988 ◽  
Vol 46 ◽  
pp. 300-301
Author(s):  
C. S. Bricker ◽  
S. R. Barnum ◽  
B. Huang ◽  
J. G. Jaworskl
Keyword(s):  
Fatty Acid ◽  
Light Intensity ◽  
Acid Content ◽  
Fatty Acid Content ◽  
Anabaena Variabilis ◽  
Chloroplast Envelope ◽  
Major Constituent ◽  
Filamentous Cyanobacterium ◽  
Photosynthetic Membrane ◽  
Effect Of Light

Cyanobacteria are Gram negative prokaryotes that are capable of oxygenic photosynthesis. Although there are many similarities between eukaryotes and cyanobacteria in electron transfer and phosphorylation during photosynthesis, there are two features of the photosynthetic apparatus in cyanobacteria which distinguishes them from plants. Cyanobacteria contain phycobiliproteins organized in phycobilisomes on the surface of photosynthetic membrane. Another difference is in the organization of the photosynthetic membranes. Instead of stacked thylakolds within a chloroplast envelope membrane, as seen In eukaryotes, IntracytopIasmlc membranes generally are arranged in three to six concentric layers. Environmental factors such as temperature, nutrition and light fluency can significantly affect the physiology and morphology of cells. The effect of light Intensity shifts on the ultrastructure of Internal membrane in Anabaena variabilis grown under controlled environmental conditions was examined. Since a major constituent of cyanobacterial thylakolds are lipids, the fatty acid content also was measured and correlated with uItrastructural changes. The regulation of fatty acid synthesis in cyanobacteria ultimately can be studied if the fatty acid content can be manipulated.

Detector strategies for environmental scanning electron microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1296-1297
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Vacuum ◽  
Environmental Scanning Electron Microscopy ◽  
Charge Carriers ◽  
Environmental Scanning ◽  
Surface Information ◽  
X Ray ◽  
Detector Electrode ◽  
Electrons And Ions ◽  
Low Energy Electrons ◽  
Environmental Sem

Environmental SEM operate at specimen chamber pressures of ∼20 torr (2.7 kPa) allowing stabilization of liquid water at room temperature, working on rugged insulators, and generation of an environmental secondary electron (ESE) signal. All signals available in conventional high vacuum instruments are also utilized in the environmental SEM, including BSE, SE, absorbed current, CL, and X-ray. In addition, the ESEM allows utilization of the flux of charge carriers as information, providing exciting new signal modes not available to BSE imaging or to conventional high vacuum SEM.In the ESEM, at low vacuum, SE electrons are collected with a “gaseous detector”. This detector collects low energy electrons (and ions) with biased wires or plates similar to those used in early high vacuum SEM for SE detection. The detector electrode can be integrated into the first PLA or positioned at any other place resulting in a versatile system that provides a variety of surface information.

Direct imaging of charge transfer

1996 ◽  
Vol 54 ◽  
pp. 680-681
Author(s):  
Yimei Zhu ◽  
J. Tafto
Keyword(s):  
Charge Transfer ◽  
Electron Diffraction ◽  
Scattering Amplitude ◽  
High Temperature Superconductors ◽  
Charge Carriers ◽  
Image Charge ◽  
Net Charge ◽  
Long Time ◽  
Electron Holes ◽  
First Time

The electron holes confined to the CuO2-plane are the charge carriers in high-temperature superconductors, and thus, the distribution of charge plays a key role in determining their superconducting properties. While it has been known for a long time that in principle, electron diffraction at low angles is very sensitive to charge transfer, we, for the first time, show that under a proper TEM imaging condition, it is possible to directly image charge in crystals with a large unit cell. We apply this new way of studying charge distribution to the technologically important Bi2Sr2Ca1Cu2O8+δ superconductors.Charged particles interact with the electrostatic potential, and thus, for small scattering angles, the incident particle sees a nuclei that is screened by the electron cloud. Hence, the scattering amplitude mainly is determined by the net charge of the ion. Comparing with the high Z neutral Bi atom, we note that the scattering amplitude of the hole or an electron is larger at small scattering angles. This is in stark contrast to the displacements which contribute negligibly to the electron diffraction pattern at small angles because of the short g-vectors.

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