The effect of fluorine-based plasma treatment on morphology and chemical surface composition of biocompatible silicone elastomer

X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) have been used to investigate the effect of reactive ion etching (RIE) on poly(methylhydrogensiloxane-co-dimethylsiloxane) surface in fluorine-based plasmas. Polysiloxane layers supported on the standard silicon wafers were etched using SF₆ + O₂ or CF₄ + O₂ plasmas. SEM studies show that the polysiloxane morphology depends on plasma chemical composition strongly. Presence of a columnar layer likely covered with a fluorine rich compound was found on the elastomer surface after the CF₄ + O₂ plasma exposure. After the SF₆ + O₂ or CF₄ + O₂ plasma treatment the polysiloxane surface enriches with fluorine or with fluorine and aluminum, respectively. Different morphologies and surface chemical compositions of the silicone elastomer etched in both plasmas indicate different etching mechanisms.     

The effects of external influences on the distribution of polarization in calcium barium niobate crystals of differing composition

The pyroelectric properties and state of polarization of calcium barium niobate single crystals Ca_xBa_1–xNb₂O₆ (CBN) with x = 0.28, 0.30, and 0.32 are studied. It is shown that in contrast to CBN30 and CBN32 crystals, the effect of the alternating electric fields higher than the coercive field changes the state of polarization in the surface layer of the CBN28 crystal. At the same time, thermal cycling to temperatures higher than the Curie point leads to the formation of a system of antiparallel domains in CBN30 and CBN32 crystals, and to complete depolarization of CBN28 crystals.     

The effect of chemical composition of a crystallization medium on the cBN stoichiometry

Abstract

The effect of chemical composition of the crystallization medium in synthesis on and some properties of cubic boron nitride (cBN) has been studied. Cubic BN crystals with the lowest free boron content and a boron-nitrogen ratio close to the stoichiometric one are grown in a multicomponent crystallization medium in a Li₃N-BN system. These crystals are characterized by a higher strength and thermal stability.     

The influence of chemical composition on models of Type Ia supernovae

Type Ia supernovae are bright stellar explosions distinguished by standardizable light curves that allow for their use as distance indicators for cosmological studies. Despite the highly successful use of these events in this capacity, many fundamental questions remain. Contemporary research investigates how properties of the progenitor system that follow from the host galaxy such as composition and age influence the brightness of an event with the goal of better understanding and assessing the intrinsic scatter in the brightness. We provide an overview of these supernovae and proposed progenitor systems, all of which involve one or more compact stars known as white dwarfs. We describe contemporary research investigating how the composition and structure of the progenitor white dwarf systematically influences the explosion outcome assuming the progenitor is a single white dwarf that has gained mass from a companion. We present results illustrating some of these systematic effects from our research.     

Influence of chemical composition and thermal effects on the optical band gap of CdSXSe1−X thin films

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 1, pp. 86–89, July, 1989.     

Changes in surface stress, morphology and chemical composition of silica and silicon nitride surfaces during the etching by gaseous HF acid

HF acid attack of SiO₂ and Si₃N₄ substrates is analyzed to improve the sensitivity of a sensor based on microcantilever. Ex situ analysis of the etching using XPS, SIMS and AFM show significant changes in the anisotropy and the rate of the etching of the oxides on SiO₂ and Si₃N₄ surface. Those differences influence the kinetic evolution of the plastic bending deflection of the cantilever coated with SiO₂ and Si₃N₄ layer, respectively. The linear dependence between the HF concentration and the Si₃N₄ cantilever bending corresponds to a deep attack of the layer whereas the non-linear behavior observed for SiO₂ layer can be explained by a combination of deep and lateral etching. The cantilever bending is discussed in terms of free surface energy, layer thickness and grain size.     

Effect of thermal and chemical treatment on the structure and composition of nanodiamonds

The effect of chemical and thermal treatment on structural characteristics and chemical composition of detonation synthesis ultradispersed diamonds (UDDs) was studied. UDDs of five different producers were compared. Special attention was paid to structural characteristics of samples (size of coherent scattering regions, aggregation), which were determined by SEM, AFM, and X-ray diffraction methods. Impurities were analyzed by methods of mass spectrometry, atomic and absorption analysis, and X-ray spectral analysis.     

The effects of size distribution on the stabiity of bubbly flow

The effects of the radius distribution of the bubbles on the stability of bubbly flow are investigated. The equations of motion are linearized and a dispersion relation is obtained which strongly depends on the shape of the size distribution function. An example is calculated which indicates that a class of initial distribution functions might give rise to unstable oscillations.     

Effects of chemical composition on the quenching of chemiluminescence by oxygen

The Stern-Volmer equation is obeyed by the oxygen quenching of chemiluminescence in the oxidation of hydrocarbons. Deviations occur at low hydrocarbon concentrations because there are several different causes of hemiluminescence.     

Fabrication processing effects on the microstructure and morphology of erbium film

The effect of substrate temperature on the microstructure and the morphology of erbium film are systematically investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). All the erbium films are grown by electron-beam vapor deposition (EBVD). A novel preparation method for observing the cross-section morphology of the erbium film is developed. The films deposited at 200°C have (002) preferred orientation, and the films deposited at 450°C have a mixed (100) and (101) texture, due to the different growth mechanisms of surface energy minimization and recrystallization, respectively. The peak positions and the full widths at half maximum (FWHMs) of erbium diffraction lines (100), (002), and (101) shift towards higher angles and decrease with the increasing substrate temperature in a largely uniform manner, respectively. Also, the lattice constants decrease with increasing temperature. The transition in the film stresses can be used to interpret the changes in peak positions, FWHMs, and lattice constants. The stress is compressive for the as-growth films, and is counteracted by the tensile stress formed during the process of temperature cooling to room temperature. The tensile stress mainly originates from the difference in the coefficients of thermal expansion of the substrate-film couple.     

Influence of sintering conditions on chemical composition of NASICON

The influence of various sintering conditions on the chemical composition and on some physical properties of undoped and CaO or MgO doped NASICON ceramics was studied. The synthesized material was characterized by a few experimental techniques, including the wet chemical analysis and the admittance spectroscopy. The dopants were found to be located in the glassy phase formed during sintering of NASICON material. The electrical properties of NASICON were strongly affected by sintering conditions.     

The effects of chemical pretreatment on tribocharging of density fraction coal

Dry triboelectric separation of coal depends on tribocharge difference of the coal and gangue mineral. The coal samples of different density fraction prepared by sink-and-float method were pretreated by chemicals and their effects on the tribocharge performance with stainless steel were studied by measuring the charge-to-mass and relative dielectric constant. The results show the tribocharging performance of middle density fraction coal is the worst compared with other density fractions. The charge of lower density fraction was increased by chemical conditioning with light diesel oil, ammonia, and kerosene, while the charge of higher density fraction was decreased with ethanol and lignin.     

The effects of chemical etching of porous silicon on Raman spectra

We have investigated the effects of chemical etching on Raman spectra of porous silicon. The as-anodized porous silicon consisted mainly of crystalline silicon, as indicated by the Raman spectra. The background in the spectrum was strong, indicating that the porous silicon surface was rough due to the presence of pores. When chemical etching was performed five times, the Raman spectrum revealed the presence of spherically shaped nanocrystalline silicon whose diameter was around 3.5 nm. Further chemical etching, however, extinguished the nanocrystallites, in addition to smoothing the surface morphology.     

Structure and morphology of chemical bath-deposited CdS films and clusters

Thin films of cadmium sulfide have been deposited on glass substrates and the structural properties of films have been investigated using scanning electron microscopy and X-ray diffraction techniques. The films consist of domains (groups of grains) and weakly bound grain clusters. The structural parameters of grains, domains and clusters and the effect of film thickness on these parameters are reported. From the measurement of lattice constants in CdS films and in free CdS clusters, it has become evident that the films on glass substrates have a tensile strain along their planes. The effect of thermal annealing on the partial relaxation of the strain is discussed. Received: 29 January 2001 / Accepted: 30 January 2001 / Published online: 3 May 2001