Optoelectronic Properties of Plasma CVD a-Si:H Modified by Filament-Generated Atomic H

1992 ◽  
Vol 258 ◽  
Author(s):  
Y.M. Li ◽  
I. An ◽  
M. Gunes ◽  
R.M. Dawson ◽  
R.W. Collins ◽  
...  
Keyword(s):  
Film Thickness ◽  
Real Time ◽  
Chemical Potential ◽  
Defect Density ◽  
Plasma Deposition ◽  
Plasma Cvd ◽  
Near Surface ◽  
Optical Gap ◽  
New Material ◽  
Control Samples

ABSTRACTWe have studied a-Si:H prepared by alternating plasma deposition with atomic H treatments performed with a heated W filament. Real time spectroscopie ellipsometry provides the evolution of film thickness, optical gap, and a measure of the fraction of Si-Si bonds broken in the near-surface (200 Å) during H-exposure of single films. This information guided us to the desired parameters for the H-treatments. Here, we concentrate on a weak hydrogenation regime characterized by minimal etching, a higher H content by 2 at.%, and a larger optical gap by 0.02 eV for the growth/hydrogenation structures in comparison to continuously deposited control samples. This new material has shown an improvement in the defect density in the light-soaked state in comparison to the control samples. This may result from stabilization of the Si structure due to an increase in the H chemical potential in the a-Si:H.

scholarly journals Near-surface real-time seismic imaging using parsimonious interferometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sherif M. Hanafy ◽  
Hussein Hoteit ◽  
Jing Li ◽  
Gerard T. Schuster
Keyword(s):  
Fluid Flow ◽  
Real Time ◽  
Temporal Resolution ◽  
Seismic Imaging ◽  
Time Lapse ◽  
Rock Properties ◽  
Recording Time ◽  
Near Surface ◽  
Arrival Times ◽  
Order Of Magnitude

AbstractResults are presented for real-time seismic imaging of subsurface fluid flow by parsimonious refraction and surface-wave interferometry. Each subsurface velocity image inverted from time-lapse seismic data only requires several minutes of recording time, which is less than the time-scale of the fluid-induced changes in the rock properties. In this sense this is real-time imaging. The images are P-velocity tomograms inverted from the first-arrival times and the S-velocity tomograms inverted from dispersion curves. Compared to conventional seismic imaging, parsimonious interferometry reduces the recording time and increases the temporal resolution of time-lapse seismic images by more than an order-of-magnitude. In our seismic experiment, we recorded 90 sparse data sets over 4.5 h while injecting 12-tons of water into a sand dune. Results show that the percolation of water is mostly along layered boundaries down to a depth of a few meters, which is consistent with our 3D computational fluid flow simulations and laboratory experiments. The significance of parsimonious interferometry is that it provides more than an order-of-magnitude increase of temporal resolution in time-lapse seismic imaging. We believe that real-time seismic imaging will have important applications for non-destructive characterization in environmental, biomedical, and subsurface imaging.

Strain Analysis in Thin La1−xCaxMnO3 Films by Grazing Incidence X-ray Scattering

1999 ◽  
Vol 602 ◽  
Author(s):  
M. Petit ◽  
L. J. Martinez-Miranda ◽  
M. Rajeswari ◽  
A. Biswas ◽  
D. J. Kang ◽  
...  
Keyword(s):  
Film Thickness ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Strain Analysis ◽  
Grazing Incidence ◽  
Relaxation Processes ◽  
Near Surface ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractWe have performed depth profile analyses of the lattice parameters in epitaxial thin films of La1−xCaxMno3 (LCMO), where x = 0.33 or 0.3, to understand the evolution of strain relaxation processes in these materials. The analyses were done using Grazing Incidence X-ray Scattering (GIXS) on films of different thicnesses on two different substrates, (100) oriented LaAlO3 (LAO), with a lattice mismatch of ∼2% and (110) oriented NGO, with a lattice mismatch of less than 0.1%. Films grown on LAO can exhibit up to three in-plane strained lattice constants, corresponding to a slight orthorhombic distortion of the crystal, as well as near-surface and columnar lattice relaxation. As a function of film thickness, a crossover from a strained film to a mixture of strained and relaxed regions in the film occurs in the range of 700 Å. The structural evolution at this thickness coincides with a change in the resistivity curve near the metalinsulator transition. The in-plane compressive strain has a range of 0.2 – 1.5%, depending on the film thickness for filsm in the range of 400 - 1500 A.

Elastomeric Conductive Ipn From Polyaniline And Fullerene-Based Networks

1995 ◽  
Vol 413 ◽  
Author(s):  
Lee Y. Wang ◽  
Long Y. Chiang ◽  
C. S. Kuo ◽  
J. G. Lin ◽  
C. Y. Huang
Keyword(s):  
Ammonium Persulfate ◽  
Cross Linking ◽  
Synthetic Method ◽  
Near Surface ◽  
Bulk Properties ◽  
Ambient Temperatures ◽  
Polyurethane Networks ◽  
New Material ◽  
Conductive Polyaniline ◽  
Polyhydroxylated Fullerenes

ABSTRACTPolyhydroxylated fullerenes were utilized as an efficient hyper cross-linking agent in the synthesis of polyurethane networks. The resultant elastomers exhibited greatly enhanced thermal stability in comparison with those of the corresponding linear polyurethane and analogous elastomers, which were cross-linked by 1,1,1- tris(hydroxymethyl)ethane. A synthetic method leading to the preparation of a thin layer of conductive polyaniline/polyurethane IPN at the near surface of a fullerenol- based elastomeric substrate was demonstrated, using aqueous ammonium persulfate as an oxidizing agent in the presence of HCI. This new material exhibits a conductivity of 2.0 S/cm at ambient temperatures with the retention of most bulk properties of the parent elastomer, such as elongation and tensile strength at break.

scholarly journals Mechanisms of Enhanced Ionic Conduction at Interfaces in Ceramics

1994 ◽  
Vol 357 ◽  
Author(s):  
D. Lubben ◽  
F. A. Modine
Keyword(s):  
Film Thickness ◽  
Ionic Conduction ◽  
Defect Density ◽  
Ionic Conductivities ◽  
Dislocation Motion ◽  
Extended Defects ◽  
Epitaxial Relationship ◽  
Extended Defect ◽  
Charge Layer ◽  
Fine Grained

AbstractA large enhancement in the ionic conductivity of certain compounds occurs when the compound is produced as a composite material containing a finely-dispersed non-conductor such as SiO2 or Al2O3 This effect has been reported on for more than 20 years, and it is well established that the enhancement is associated with the presence of interfaces. The popular explanation has been based on a model which contends that the enhancement is due to a space-charge layer which forms to compensate a net charge layer at an interface. A different model proposes that extended defects such as dislocations and grain boundaries, either resulting from or stabilized by the interface, are responsible for the enhancement. This paper describes recent experiments which strongly support the latter model. The ionic conductivities of LiI and CaF2 thin films grown on sapphire(0001) substrates were monitored in-situ during deposition as a function of film thickness and deposition conditions. LiI films grown at 27°C exhibited a region of enhanced conduction within 100 nm of the substrate and a lesser enhancement as the film thickness was increased further. This conduction enhancement was not stable but annealed out with a characteristic log(time) dependence. The observed annealing behavior was fit with a model based on dislocation motion which implies that the increase in conduction near the interface is due to extended defects generated during the growth process. LiI films grown at higher temperatures (100°C) in order to reduce the grown-in defects showed no interfacial conduction enhancement. X-ray diffraction measurements suggest that these high-temperature LiI films nucleate as faceted epitaxial islands with a stable misfit dislocation density defined by the epitaxial relationship between the substrate and film. CaF2 films grown at 200°C showed a behavior similar to the 27°C LiI films, with a region of thermally unstable enhanced conduction that occurs within 10 nm of the substrate. Amorphous Al2O3 films deposited over the CaF2 layers created no additional enhancement but did increase the stability of the conduction, consistent with an extended defect model. Simultaneous deposition of CaF2 and Al2O3 produced films consisting of very-fine-grained CaF2 and particles of amorphous Al2O23 (5-10 nm grain and particle size) and a high defect density which was stable even well above the growth temperature. Measured conduction in the composite at 200°C was approximately 360 times that of bulk CaF2.

Digital Images

2011 ◽  
Vol 2 (1) ◽  
pp. 27-41 ◽  
Author(s):  
Linda Matthews ◽  
Gavin Perin
Keyword(s):  
Public Space ◽  
Real Time ◽  
Urban Space ◽  
Three Dimensional ◽  
Digital Systems ◽  
Digital Information ◽  
New Material ◽  
The Relationship ◽  
Cultural Shifts ◽  
Material Form

The valence of any visual paradigm and its accompanying technologies is subject to the contingencies of political regimes and cultural shifts. The instigation, implementation and even reconfiguring of any associated technological system effects a translation and adjustment to the structure and use of these supporting mechanisms that both re-defines the relationship between object and viewer and ultimately influences its translation into material form. The permeation of digital systems throughout contemporary urban space is typified by Internet Protocol webcam systems, instigated by civic authorities for surveillance and the imagistic promotion of iconic city form. This paper examines how this system’s reception and subsequent translation of transmitted data signals into digital information not only presents new material to mediate people’s engagement with public space, but moreover, how it presents new opportunities for the designer to materialize its three-dimensional form within the spatial ambiguity of virtual and real-time environments.

scholarly journals A Data-Driven Approach for Daily Real-Time Estimates and Forecasts of Near-Surface Soil Moisture

2017 ◽  
Vol 18 (3) ◽  
pp. 837-843 ◽  
Author(s):  
Randal D. Koster ◽  
Rolf H. Reichle ◽  
Sarith P. P. Mahanama
Keyword(s):  
United States ◽  
Soil Moisture ◽  
Real Time ◽  
Surface Soil ◽  
Data Driven ◽  
Surface Soil Moisture ◽  
Near Surface ◽  
Time Estimates ◽  
Data Driven Approach ◽  
Global Surface

Abstract NASA’s Soil Moisture Active Passive (SMAP) mission provides global surface soil moisture retrievals with a revisit time of 2–3 days and a latency of 24 h. Here, to enhance the utility of the SMAP data, an approach is presented for improving real-time soil moisture estimates (nowcasts) and for forecasting soil moisture several days into the future. The approach, which involves using an estimate of loss processes (evaporation and drainage) and precipitation to evolve the most recent SMAP retrieval forward in time, is evaluated against subsequent SMAP retrievals themselves. The nowcast accuracy over the continental United States is shown to be markedly higher than that achieved with the simple yet common persistence approach. The accuracy of soil moisture forecasts, which rely on precipitation forecasts rather than on precipitation measurements, is reduced relative to nowcast accuracy but is still significantly higher than that obtained through persistence.

scholarly journals GPS–Cellular Drifter Technology for Coastal Ocean Observing Systems

2005 ◽  
Vol 22 (9) ◽  
pp. 1381-1388 ◽  
Author(s):  
J. Carter Ohlmann ◽  
Peter F. White ◽  
Andrew L. Sybrandy ◽  
P. Peter Niiler
Keyword(s):  
Real Time ◽  
Coastal Ocean ◽  
Hf Radar ◽  
Near Surface ◽  
Spatial And Temporal Scales ◽  
Time Space ◽  
Position Data ◽  
Ocean Observing ◽  
Ocean Observing Systems ◽  
Observing Systems

Abstract A drifter for observing small spatial and temporal scales of motion in the coastal zone is presented. The drifter uses GPS to determine its position, and the Mobitex terrestrial cellular communications system to transmit the position data in near–real time. This configuration allows position data with order meter accuracy to be sampled every few minutes and transmitted inexpensively. Near-real-time transmission of highly accurate position data enables the drifters to be retrieved and redeployed, further increasing economy. Drifter slip measurements indicate that the drifter follows water to within ∼1–2 cm s−1 during light wind periods. Slip values >1 cm s−1 are aligned with the direction of surface wave propagation and are 180° out of phase, so that the drifter “walks” down waves. Nearly 200 drifter tracks collected off the Santa Barbara, California, coast show comparisons with high-frequency (HF) radar observations of near-surface currents that improve by roughly 50% when the average drifter values are computed from more than 25 observations within a 2-km square HF radar bin. The improvement is the result of drifter resolution of subgrid-scale eddies that are included in time–space-averaged HF radar fields. The average eddy kinetic energy on 2-km space and hour time scales is 25 cm2 s−2, when computed for bins with more than 25 drifter observations. Comparisons with trajectories that are computed from HF radar data show mean separation velocities of 5 and 9 cm s−1 in the along- and across-shore directions, respectively. The drifters resolve scales of motion that are not present in HF radar fields, and are thus complementary to HF radar in coastal ocean observing systems.

Improved Light Soaking Stability of R.F. Sputter Deposited Amorphous Silicon

1991 ◽  
Vol 219 ◽  
Author(s):  
A. Wynveen ◽  
J. Fan ◽  
J. Kakalios ◽  
J. Shinar
Keyword(s):  
Amorphous Silicon ◽  
Hydrogen Content ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Dark Conductivity ◽  
Initial Defect ◽  
Optical Gap ◽  
Sputter Deposited ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous

ABSTRACTStudies of r.f. sputter deposited hydrogenated amorphous silicon (a-Si:H) find that the light induced decrease in the dark conductivity and photoconductivity (the Staebler-Wronski effect) is reduced when the r.f. power used during deposition is increased. The slower Staebler-Wronski effect is not due to an increase in the initial defect density in the high r.f. power samples, but may result from either the lower hydrogen content or the smaller optical gap found in these films.

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