The Physics of Plasma Deposition of Microcrystalline Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
B. Drevillon ◽  
I. Solomon ◽  
M. Fang
Keyword(s):  
Chemical Equilibrium ◽  
Plasma Deposition ◽  
Selective Etching ◽  
Microcrystalline Silicon ◽  
Hydrogen Etching ◽  
Hydrogen Plasmas ◽  
The Many ◽  
Partial Chemical ◽  
Uv Range

ABSTRACTThe growth of microcrystalline silicon (μc-Si), deposited by a succession of silane and hydrogen plasmas, is investigated in situ by ellipsometry in the visible and near UV-range. It is found that the amorphous tissue is more affected by the hydrogen etching than the crystallites. The model of “selective etching” emerges from these measurements. Although this model is compatible with the “partial chemical equilibrium” of Vep̌ek, it is somewhat more general and explains the porous nature of the (μc-Si) as well as the many atomic layers deposition-etching sequences.

Investigations on the Real-Time Monitoring of the Crystallinity of Hydrogenated Microcrystalline Silicon Films

2003 ◽  
Vol 762 ◽  
Author(s):  
Christoph Ross ◽  
Friedhelm Finger ◽  
Reinhard Carius
Keyword(s):  
Spectroscopic Ellipsometry ◽  
Time Resolution ◽  
Deposition Process ◽  
Silicon Films ◽  
Microcrystalline Silicon ◽  
Hydrogenated Silicon ◽  
20 Nm ◽  
Good Agreement ◽  
Uv Range

AbstractA method for monitoring the evolution of the crystallinity during the deposition of thin hydrogenated silicon films by using in situ spectroscopic ellipsometry is presented. The crystallinity of the topmost 10-20 nm of a film is derived from the analysis of the shape of ellipsometric spectra in the UV range. The values are closely related to parameters of the deposition process and in good agreement with Raman scattering results. Examples of different kinds of microcrystalline silicon films are shown. Improvements of the time resolution and/or accuracy are discussed. The method turns out to be well suited for process control.

Plasma deposition of microcrystalline silicon: the selective etching model

1993 ◽  
Vol 164-166 ◽  
pp. 989-992 ◽  
Author(s):  
I. Solomon ◽  
B. Drévillon ◽  
H. Shirai ◽  
N. Layadi
Keyword(s):  
Plasma Deposition ◽  
Selective Etching ◽  
Microcrystalline Silicon

Plasma Surface Interaction During the Growth of Semiconductor Thin Films Studied byin Situ Infrared Ellipsometry

1991 ◽  
Vol 237 ◽  
Author(s):  
N. Blayo ◽  
B. Drevillon
Keyword(s):  
Film Surface ◽  
Surface Interactions ◽  
Microcrystalline Silicon ◽  
Hydrogen Etching ◽  
Plasma Surface ◽  
Plasma Surface Interactions ◽  
Glass Substrates ◽  
Infrared Ellipsometry ◽  
Semiconductor Thin Films

ABSTRACTThe early stages of the growth of plasma deposited amorphous silicon (a-Si:H) and microcrystalline silicon (μc-Si) on glass substrates are investigated by in situ infrared phase modulated ellipsometry (IRPME) in the silicon-hydrogen stretching mode region. μc-Si are prepared by alternating SiH4 and H2 plasmas. New insights on the plasma-surface interactions during the growth of these films are given. During the deposition of the first 20 Å of a-Si:H, the hydrogen is incorporated as SiH2. During the further growth of a-Si:H the SiH2 bonds are located at the film surface inside a very thin hydrogen rich overlayer. During the deposition of the first 10–20 Å of μc-Si, the SiH2 bonds are predominantly removed by the H2 plasma, the material being amorphous. After this selective removal of the SiH2 groups, a transition from amorphous to microcrystalline growm is observed. A systematic hydrogen etching during the further growth of μc-Si is observed.

scholarly journals A general Cluster data and global MHD simulation comparison

2008 ◽  
Vol 26 (11) ◽  
pp. 3411-3428 ◽  
Author(s):  
P. Daum ◽  
M. H. Denton ◽  
J. A. Wild ◽  
M. G. G. T. Taylor ◽  
J. Šafránková ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Mhd Simulation ◽  
Global Context ◽  
Cluster Data ◽  
Verification Methods ◽  
Modelling Studies ◽  
Global Mhd Simulation ◽  
The Many

Abstract. Among the many challenges facing the space weather modelling community today, is the need for validation and verification methods of the numerical models available describing the complex nonlinear Sun-Earth system. Magnetohydrodynamic (MHD) models represent the latest numerical models of this environment and have the unique ability to span the enormous distances present in the magnetosphere, from several hundred kilometres to several thousand kilometres above the Earth's surface. This makes it especially difficult to develop verification and validation methods which posses the same range spans as the models. In this paper we present a first general large-scale comparison between four years (2001–2004) worth of in situ Cluster plasma observations and the corresponding simulated predictions from the coupled Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) MHD code. The comparison between the in situ measurements and the model predictions reveals that by systematically constraining the MHD model inflow boundary conditions a good correlation between the in situ observations and the modeled data can be found. These results have an implication for modelling studies addressing also smaller scale features of the magnetosphere. The global MHD simulation can therefore be used to place localised satellite and/or ground-based observations into a global context and fill the gaps left by measurements.

scholarly journals Observation of microstructure change during freeze-drying by in-situ X-ray Computed Tomography

2018 ◽  
Author(s):  
Kyuya Nakagawa ◽  
Shinri Tamiya ◽  
Shu Sakamoto ◽  
Gabsoo Do ◽  
Shinji Kono ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Freeze Drying ◽  
Glassy State ◽  
Structural Deformation ◽  
Microstructure Formation ◽  
Microstructure Change ◽  
X Ray ◽  
X Ray Computed ◽  
The Many

X-ray computed tomography technique was used to observe microstructure formation during freeze-drying. A specially designed vacuum freeze-drying stage was equipped at the X-ray CT stage, and the frozen and dried microstructures of dextrin solutions were successfully observed. It was confirmed that the many parts of the pore microstructures formed as a replica of the original ice microstructures, whereas some parts formed as a consequence of the dehydration dependent on the relaxation level of the glassy phases, suggesting that the post-freezing annealing is advantageous for avoiding quality loss that relates to the structural deformation of glassy matters. Keywords: freeze-drying; X-ray CT; ice microstructure; glassy state

scholarly journals Advances in Polyhydroxyalkanoate Nanocarriers for Effective Drug Delivery: An Overview and Challenges

Nanomaterials ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 175
Author(s):  
Priyanka Prakash ◽  
Wing-Hin Lee ◽  
Ching-Yee Loo ◽  
Hau Seung Jeremy Wong ◽  
Thaigarajan Parumasivam
Keyword(s):  
Drug Delivery ◽  
Targeted Delivery ◽  
In Situ Polymerization ◽  
Drug Loading ◽  
Controlled Drug Release ◽  
Production Costs ◽  
Natural Polymers ◽  
High Production ◽  
The Many

Polyhydroxyalkanoates (PHAs) are natural polymers produced under specific conditions by certain organisms, primarily bacteria, as a source of energy. These up-and-coming bioplastics are an undeniable asset in enhancing the effectiveness of drug delivery systems, which demand characteristics like non-immunogenicity, a sustained and controlled drug release, targeted delivery, as well as a high drug loading capacity. Given their biocompatibility, biodegradability, modifiability, and compatibility with hydrophobic drugs, PHAs often provide a superior alternative to free drug therapy or treatments using other polymeric nanocarriers. The many formulation methods of existing PHA nanocarriers, such as emulsion solvent evaporation, nanoprecipitation, dialysis, and in situ polymerization, are explained in this review. Due to their flexibility that allows for a vessel tailormade to its intended application, PHA nanocarriers have found their place in diverse therapy options like anticancer and anti-infective treatments, which are among the applications of PHA nanocarriers discussed in this article. Despite their many positive attributes, the advancement of PHA nanocarriers to clinical trials of drug delivery applications has been stunted due to the polymers’ natural hydrophobicity, controversial production materials, and high production costs, among others. These challenges are explored in this review, alongside their existing solutions and alternatives.

scholarly journals Probing Multiscale Disorder in Pyrochlore and Related Complex Oxides in the Transmission Electron Microscope: A Review

2021 ◽  
Vol 9 ◽  
Author(s):  
Jenna L. Wardini ◽  
Hasti Vahidi ◽  
Huiming Guo ◽  
William J. Bowman
Keyword(s):  
Complex Oxides ◽  
Atomic Scale ◽  
High Dimensional ◽  
Detection Systems ◽  
Spatially Resolved ◽  
Chemical Ordering ◽  
Transmission Electron ◽  
The Many ◽  
High Dimensional Datasets

Transmission electron microscopy (TEM), and its counterpart, scanning TEM (STEM), are powerful materials characterization tools capable of probing crystal structure, composition, charge distribution, electronic structure, and bonding down to the atomic scale. Recent (S)TEM instrumentation developments such as electron beam aberration-correction as well as faster and more efficient signal detection systems have given rise to new and more powerful experimental methods, some of which (e.g., 4D-STEM, spectrum-imaging, in situ/operando (S)TEM)) facilitate the capture of high-dimensional datasets that contain spatially-resolved structural, spectroscopic, time- and/or stimulus-dependent information across the sub-angstrom to several micrometer length scale. Thus, through the variety of analysis methods available in the modern (S)TEM and its continual development towards high-dimensional data capture, it is well-suited to the challenge of characterizing isometric mixed-metal oxides such as pyrochlores, fluorites, and other complex oxides that reside on a continuum of chemical and spatial ordering. In this review, we present a suite of imaging and diffraction (S)TEM techniques that are uniquely suited to probe the many types, length-scales, and degrees of disorder in complex oxides, with a focus on disorder common to pyrochlores, fluorites and the expansive library of intermediate structures they may adopt. The application of these techniques to various complex oxides will be reviewed to demonstrate their capabilities and limitations in resolving the continuum of structural and chemical ordering in these systems.

Remediation of PCB-containing sediments using surface water diversion “dry excavation”: a case study

1996 ◽  
Vol 33 (6) ◽  
pp. 239-245 ◽  
Author(s):  
Thomas H. Praeger ◽  
Stuart D. Messur ◽  
Richard P. DiFiore
Keyword(s):  
Surface Water ◽  
Water Diversion ◽  
Regulatory Agencies ◽  
Sediment Removal ◽  
Run Off ◽  
Technical Issues ◽  
The Many ◽  
Groundwater Infiltration

Remediation of contaminated sediments presents an on-going challenge in the efforts toward improved water quality and environmental restoration. Faced with this challenge, Mercury Marine recently selected a remedial alternative that included diverting creek flow and removing approximately 5,900 in-situ cubic meters of sediments containing PCBs from an impoundment in Cedar Creek. The regulatory objective was to remove all sediment containing PCBs “to the extent practicable” from an 180-meter stretch of the impoundment. A remedial investigation was conducted to collect the data necessary to characterize the site and prepare a remedial design. Technical issues involved with dry excavation that were critical to implementing this alternative included: channel diversion, sediment characterization, pond dewatering, wastewater treatment, groundwater infiltration, surface water run-off, and sediment removal, handling and disposal. Mercury Marine and its engineering staff found sediment removal by dry excavation to be a labor intensive and costly means of remediating the PCB-affected sediments at this site. Before implementing dry excavation at any site, owners, consultants, and regulatory agencies must realize the many limitations of this alternative and give special consideration to site conditions, engineering, and planning.

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