scholarly journals Particle Surface Modification in the Near-Electrode Region of an RF Discharge

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2931
Author(s):  
Evgenii Aleksandrovich Kononov ◽  
Mikhail Mikhailovich Vasiliev ◽  
Elena Valeryevna Vasilieva ◽  
Oleg Fedorovich Petrov
Keyword(s):  
Discharge Chamber ◽  
Particle Surface ◽  
Metal Coating ◽  
Rf Discharge ◽  
Melamine Formaldehyde ◽  
Plasma Exposure ◽  
Lower Electrode ◽  
Electrode Region ◽  
Particle Coating ◽  
Composition And Structure

The results of a study on particles’ surfaces after being exposed to the near-electrode region of a radio frequency (RF) discharge are presented. It was experimentally displayed that metal starts being deposited on the surface of particles levitating above the lower electrode of the discharge chamber after switching the RF discharge on. For melamine-formaldehyde (MF) particles, the appearance of an island metal coating is observed after 30 min of plasma exposure. Eroded electrodes and elements of the gas discharge chamber may serve as a source of deposited material. In addition, an analysis of the surface and composition of particles placed on the upper electrode after 6 h of plasma exposure is presented. We reveal that the composition and structure of the particle coating changes during the experiment. The MF particles under exposure become eroded, and needle-like structures containing metals are formed on their surface. We also observe the formation of columnar structures from the products of erosion of electrodes on particles with a metal coating.

scholarly journals PECVD of Hexamethyldisiloxane Coatings Using Extremely Asymmetric Capacitive RF Discharge

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2147
Author(s):  
Žiga Gosar ◽  
Janez Kovač ◽  
Denis Đonlagić ◽  
Simon Pevec ◽  
Gregor Primc ◽  
...  
Keyword(s):  
Thin Films ◽  
Gas Phase ◽  
Discharge Chamber ◽  
Depth Profiling ◽  
Dust Particles ◽  
Rf Discharge ◽  
Plasma Parameters ◽  
Entire Volume ◽  
Partial Pressures ◽  
Pressure Discharge

An extremely asymmetric low-pressure discharge was used to study the composition of thin films prepared by PECVD using HMDSO as a precursor. The metallic chamber was grounded, while the powered electrode was connected to an RF generator. The ratio between the surface area of the powered and grounded electrode was about 0.03. Plasma and thin films were characterised by optical spectroscopy and XPS depth profiling, respectively. Dense luminous plasma expanded about 1 cm from the powered electrode while a visually uniform diffusing plasma of low luminosity occupied the entire volume of the discharge chamber. Experiments were performed at HMDSO partial pressure of 10 Pa and various oxygen partial pressures. At low discharge power and small oxygen concentration, a rather uniform film was deposited at different treatment times up to a minute. In these conditions, the film composition depended on both parameters. At high powers and oxygen partial pressures, the films exhibited rather unusual behaviour since the depletion of carbon was observed at prolonged deposition times. The results were explained by spontaneous changing of plasma parameters, which was in turn explained by the formation of dust in the gas phase and corresponding interaction of plasma radicals with dust particles.

Contactless method for studying the parameters of the electrode region of an RF discharge

2002 ◽  
Vol 28 (12) ◽  
pp. 1001-1007
Author(s):  
A. F. Aleksandrov ◽  
V. A. Ryaby ◽  
V. P. Savinov ◽  
V. G. Yakunin
Keyword(s):  
Rf Discharge ◽  
Contactless Method ◽  
Electrode Region

Distribution nucleation: Quantifying liquid distribution on the particle surface using the dimensionless particle coating number

2013 ◽  
Vol 92 ◽  
pp. 134-145 ◽  
Author(s):  
Waithira I.J. Kariuki ◽  
Ben Freireich ◽  
Rachel M. Smith ◽  
Martin Rhodes ◽  
Karen P. Hapgood
Keyword(s):  
Particle Surface ◽  
Liquid Distribution ◽  
Particle Coating

scholarly journals Towards the identification of molecular constituents associated with the surfaces of isoprene-derived secondary organic aerosol (SOA) particles

2014 ◽  
Vol 14 (5) ◽  
pp. 2303-2314 ◽  
Author(s):  
C. J. Ebben ◽  
B. F. Strick ◽  
M. A. Upshur ◽  
H. M. Chase ◽  
J. L. Achtyl ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Particle Surface ◽  
Particle Growth ◽  
Organic Aerosol ◽  
Abundant Species ◽  
Fused Silica ◽  
Oxidation Products ◽  
Sum Frequency ◽  
Particle Material ◽  
Composition And Structure

Abstract. Secondary organic aerosol (SOA) particle formation ranks among the least understood chemical processes in the atmosphere, rooted in part in the lack of knowledge about chemical composition and structure at the particle surface, and little availability of reference compounds needed for benchmarking and chemical identification in pure and homogenous form. Here, we synthesize and characterize SOA particle constituents consisting of the isoprene oxidation products α-, δ-, and cis- and trans-β-IEPOX (isoprene epoxide), as well as syn- and anti-2-methyltetraol. Paying particular attention to their phase state (condensed vs. vapor), we carry out a surface-specific and orientationally selective chemical analysis by vibrational sum frequency generation (SFG) spectroscopy of these compounds in contact with a fused silica window. Comparison to the vibrational SFG spectra of synthetic isoprene-derived SOA particle material prepared at the Harvard Environmental Chamber yields a plausible match with trans-β-IEPOX, suggesting it is an abundant species on their surfaces, while the other species studied here, if present, appear to be SFG inactive and thus likely to be localized in a centrosymmetric environment, e.g., the particle bulk. No match is found for authentic SOA particle material collected at the site of the Amazonian Aerosol Characterization Experiment (AMAZE-08) with the surface SFG spectra of the compounds surveyed here, yet we cannot rule out this mismatch being attributable to differences in molecular orientation. The implications of our findings for SOA formation are discussed in the context of condensational particle growth and reactivity.

Crystal Structure Analysis of Cu-Zr Alloys by Convergent Beam Diffraction

1981 ◽  
Vol 39 ◽  
pp. 354-355
Author(s):  
A. F. Marshall ◽  
J. W. Steeds ◽  
D. Bouchet ◽  
S. L. Shinde ◽  
R. G. Walmsley
Keyword(s):  
Crystal Structure ◽  
Point Group ◽  
Intermetallic Phase ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Ion Milling ◽  
Composition And Structure ◽  
Unit Cells ◽  
Sputter Deposited ◽  
Convergent Beam

Convergent beam electron diffraction is a powerful technique for determining the crystal structure of a material in TEM. In this paper we have applied it to the study of the intermetallic phases in the Cu-rich end of the Cu-Zr system. These phases are highly ordered. Their composition and structure has been previously studied by microprobe and x-ray diffraction with sometimes conflicting results.The crystalline phases were obtained by annealing amorphous sputter-deposited Cu-Zr. Specimens were thinned for TEM by ion milling and observed in a Philips EM 400. Due to the large unit cells involved, a small convergence angle of diffraction was used; however, the three-dimensional lattice and symmetry information of convergent beam microdiffraction patterns is still present. The results are as follows:1) 21 at% Zr in Cu: annealed at 500°C for 5 hours. An intermetallic phase, Cu3.6Zr (21.7% Zr), space group P6/m has been proposed near this composition (2). The major phase of our annealed material was hexagonal with a point group determined as 6/m.

Off-axis electron holography applied to the study of interfaces

1992 ◽  
Vol 50 (1) ◽  
pp. 244-245
Author(s):  
J.K. Weiss ◽  
M. Gajdardziska-Josifovska ◽  
M. R. McCartney ◽  
David J. Smith
Keyword(s):  
Electric Fields ◽  
Resolution Enhancement ◽  
Interfacial Structure ◽  
Atomic Scale ◽  
Bulk Property ◽  
Electron Holography ◽  
Specimen Thickness ◽  
Composition And Structure ◽  
Chemical Segregation ◽  
Diffraction Effects

Interfacial structure is a controlling parameter in the behavior of many materials. Electron microscopy methods are widely used for characterizing such features as interface abruptness and chemical segregation at interfaces. The problem for high resolution microscopy is to establish optimum imaging conditions for extracting this information. We have found that off-axis electron holography can provide useful information for the study of interfaces that is not easily obtained by other techniques.Electron holography permits the recovery of both the amplitude and the phase of the image wave. Recent studies have applied the information obtained from electron holograms to characterizing magnetic and electric fields in materials and also to atomic-scale resolution enhancement. The phase of an electron wave passing through a specimen is shifted by an amount which is proportional to the product of the specimen thickness and the projected electrostatic potential (ignoring magnetic fields and diffraction effects). If atomic-scale variations are ignored, the potential in the specimen is described by the mean inner potential, a bulk property sensitive to both composition and structure. For the study of interfaces, the specimen thickness is assumed to be approximately constant across the interface, so that the phase of the image wave will give a picture of mean inner potential across the interface.

Ultra high resolution SEM at high voltage images individual fab fragments applied as molecular label to cell surface receptors

1989 ◽  
Vol 47 ◽  
pp. 70-71
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Resolution ◽  
High Energy ◽  
Metal Coating ◽  
Beam Diameter ◽  
Surface Receptors ◽  
Surface Mobility ◽  
Metal Atoms ◽  
Shadowing Effect ◽  
Imaging Mode ◽  
Deposition Techniques

Topographic ultra high resolution can now routinely be established on bulk samples in cold field emission scanning electron microscopy with a second generation of microscopes (FSEM) designed to provide 0.5 nm probe diameters. If such small probes are used for high magnification imaging, topographic contrast is so high that remarkably fine details can be imaged on 2DMSO/osmium-impregnated specimens at ribosome surfaces even without a metal coating. On TCH/osmium-impregnated specimens topographic resolution can be increased further if the SE-I imaging mode is applied. This requires that beam diameter and metal coating thickness be made smaller than the SE range of ~1 nm and background signal contributions be reduced. Subnanometer small probes can be obtained (only) at high accelerating voltages. Subnanometer thin continuous metal films can be produced under the following conditions: self-shadowing effect between metal atoms must be reduced through appropriate deposition techniques and surface mobility of metal atoms must be diminished through high energy sputtering and/or specimen cooling.

High-resolution scanning electron microscopy in biology

1990 ◽  
Vol 48 (3) ◽  
pp. 14-15
Author(s):  
Keiichi Tanaka
Keyword(s):  
High Resolution ◽  
Immunoglobulin M ◽  
Metal Coating ◽  
Biological Macromolecules ◽  
Ultrahigh Resolution ◽  
Preparation Methods ◽  
Low Contrast ◽  
Almost All ◽  
Charging Effect ◽  
Scanning Electron

With the development of scanning electron microscope (SEM) with ultrahigh resolution, SEM became to play an important role in not only cytology but also molecular biology. However, the preparation methods observing tiny specimens with such high resolution SEM are not yet established.Although SEM specimens are usually coated with metals for getting electrical conductivity, it is desirable to avoid the metal coating for high resolution SEM, because the coating seriously affects resolution at this level, unless special coating techniques are used. For avoiding charging effect without metal coating, we previously reported a method in which polished carbon plates were used as substrate. In the case almost all incident electrons penetrate through the specimens and do not accumulate in them, when the specimens are smaller than 10nm. By this technique some biological macromolecules including ribosomes, ferritin, immunoglobulin G were clearly observed.Unfortunately some other molecules such as apoferritin, thyroglobulin and immunoglobulin M were difficult to be observed only by the method, because they had very low contrast and were easily damaged by electron beam.

Advances in ultramicrotomy for physical sciences applications

1993 ◽  
Vol 51 ◽  
pp. 710-711
Author(s):  
G. McMahon ◽  
T. Malis
Keyword(s):  
Particle Surface ◽  
Zeolite Catalysts ◽  
Physical Sciences ◽  
Pull Out ◽  
Large Particles ◽  
Novel Applications ◽  
Metal Wires ◽  
Frequent Problem ◽  
Specific Orientation ◽  
Diamond Knife

As with all techniques which are relatively new and therefore underutilized, diamond knife sectioning in the physical sciences continues to see both developments of the technique and novel applications.Technique Developments Development of specific orientation/embedding procedures for small pieces of awkward shape is exemplified by the work of Bradley et al on large, rather fragile particles of nuclear waste glass. At the same time, the frequent problem of pullout with large particles can be reduced by roughening of the particle surface, and a proven methodology using a commercial coupling agent developed for glasses has been utilized with good results on large zeolite catalysts. The same principle (using acid etches) should work for ceramic fibres or metal wires which may only partially pull out but result in unacceptably thick sections. Researchers from the life sciences continue to develop aspects of embedding media which may be applicable to certain cases in the physical sciences.

Structural Studies on the Eukaryotic Ribosome

1990 ◽  
Vol 48 (1) ◽  
pp. 256-257
Author(s):  
Adriana Verschoor ◽  
Ronald Milligan ◽  
Suman Srivastava ◽  
Joachim Frank
Keyword(s):  
Chick Embryo ◽  
3D Reconstruction ◽  
Single Particle ◽  
Mass Density ◽  
Particle Surface ◽  
Uranyl Acetate ◽  
Electron Microscopic ◽  
Eukaryotic Ribosome ◽  
Negative Stain ◽  
Reconstruction Methods

We have studied the eukaryotic ribosome from two vertebrate species (rabbit reticulocyte and chick embryo ribosomes) in several different electron microscopic preparations (Fig. 1a-d), and we have applied image processing methods to two of the types of images. Reticulocyte ribosomes were examined in both negative stain (0.5% uranyl acetate, in a double-carbon preparation) and frozen hydrated preparation as single-particle specimens. In addition, chick embryo ribosomes in tetrameric and crystalline assemblies in frozen hydrated preparation have been examined. 2D averaging, multivariate statistical analysis, and classification methods have been applied to the negatively stained single-particle micrographs and the frozen hydrated tetramer micrographs to obtain statistically well defined projection images of the ribosome (Fig. 2a,c). 3D reconstruction methods, the random conical reconstruction scheme and weighted back projection, were applied to the negative-stain data, and several closely related reconstructions were obtained. The principal 3D reconstruction (Fig. 2b), which has a resolution of 3.7 nm according to the differential phase residual criterion, can be compared to the images of individual ribosomes in a 2D tetramer average (Fig. 2c) at a similar resolution, and a good agreement of the general morphology and of many of the characteristic features is seen.Both data sets show the ribosome in roughly the same ’view’ or orientation, with respect to the adsorptive surface in the electron microscopic preparation, as judged by the agreement in both the projected form and the distribution of characteristic density features. The negative-stain reconstruction reveals details of the ribosome morphology; the 2D frozen-hydrated average provides projection information on the native mass-density distribution within the structure. The 40S subunit appears to have an elongate core of higher density, while the 60S subunit shows a more complex pattern of dense features, comprising a rather globular core, locally extending close to the particle surface.

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