Optical emission spectroscopy and actinometry in CCl4-Cl2 radiofrequency discharges

Radiofrequency discharges fed with CCl₄-Cl₂ mixtures have been studied in the pressure range 0.3 to 0.6 torr by means of emission spectroscopic actinometry with Ar, He, and N₂ as actinometers. Two different reactors, a parallel plate and a capacitively coupled tubular one, have been utilized for this study to obtain information for a large range of electron energy distributions. Analysis of the experimental results demonstrates the following: the utilization of actinometry and its range of validity, the importance of electron attachment to CCl_x species during the plasma decomposition process, and the effects of the presence of chlorine and “glowpolymer” in the discharge medium.     

Chemical vapour deposition of germanium-containing films by IR laser-induced decomposition of ethoxy(trimethyl)germane

Carbon Dioxide (CO₂) laser-induced decomposition of ethoxy(trimethyl)germane (ETG) results in a substantial stripping of organic substituents from germanium and leads to deposition of organogermanium films, the composition of which is dependent on the mode of laser irradiation. Direct absorption of laser radiation in ETG affords material rich in Germanium, while a sulfur hexafluoride (SF₆)-photosensitized process produces a deposit composed of Germanium, Carbon, Hydrogen and Oxygen. The deposited materials can be modified by chemical reactions with acetic anhydride and atmospheric moisture.     

Diagnostics and Application of the High Frequency Plasma Pencil

The so called high frequency plasma pencil is a source of highly active environment (electrons, ions, reactive radicals, excited atoms, and molecules) which can be generated at atmospheric, reduced or increased pressure, preserving a good control of the performance. The discharge can be either unipolar or bipolar. The properties of unipolar atmospheric pressure discharges are discussed on the basis of simple theoretical considerations and electric probe measurements. The plasma pencil discharge is studied by optical emission spectroscopy in the gas phase at atmospheric pressure as well as immersed in liquid using argon as a working gas. From the emission spectra the electron, vibrational and rotational temperatures are calculated for various distances from the plasma pencil electrode. Several technological applications like restoration of archaeological glass and metal artifacts, fragmentation of molecules for microelectrophoresis and plasma polymerization are summarized. An advantage of the plasma pencil is that it can be easily operated and controlled.     

Diagnostics and decomposition mechanism in radio-frequency discharges of fluorocarbons utilized for plasma etching or polymerization

Optical emission (180–800 nm) and mass spectroscopy have been used to study the CF₄, CF₄+O₂, C₂F₆, C₂F₆+H₂, CF₃Cl, and C₂F₄ decomposition in radio-frequency discharges. The analysis of the stable and unstable discharge products has allowed the suggestion of decomposition channels for the various gases and to classify the fluorinated gases according to their predominant etching or polymerizing characteristics on the basis of the active species present in the plasma. A new broad emission continuum centered at =290 nm (FWHM=66 nm) has also been identified and it has been tentatively assigned to CF⁺ ₂.     

Electrical and Optical Diagnostics of Dielectric Barrier Discharges (DBD) in He and N2 for Polymer Treatment

Synchronous, real-time optical and electrical diagnostics have been carried out on dielectric barrier discharges in flowing gases (air, He, N₂) at atmospheric pressure. A true Atmospheric Pressure Glow Discharge (APGD) is observed in N₂ when O₂ and H₂ concentrations are below 500 ppm and 2500 ppm,respectively, and the APGD regime can be beneficially modified by suitably chosen dielectric coatings. X-ray photoelectron spectroscopy (XPS) analyses of some APGD-treated polymer surfaces are presented.     

Study by Optical Spectroscopy of Bismuth Emission in a Nanosecond-Pulsed Discharge Created in Liquid Nitrogen

Time-resolved optical emission spectroscopy of nanosecond-pulsed discharges ignited in liquid nitrogen between two bismuth electrodes is used to determine the main discharge parameters (electron temperature, electron density and optical thickness). Nineteen lines belonging to the Bi I system and seven to the Bi II system could be recorded by directly plunging the optical fibre into the liquid in close vicinity to the discharge. The lack of data for the Stark parameters to evaluate the broadening of the Bi I lines was solved by taking advantage of the time-resolved information supported by each line to determine them. The electron density was found to decrease exponentially from 6.5 ± 1.5 × 10¹⁶ cm⁻³ 200 ns after ignition to 1.0 ± 0.5 × 10¹⁶ cm⁻³ after 1050 ns. The electron temperature was found to be 0.35 eV, close to the value given by Saha’s equation.     

Energy efficiency of NO removal by pulsed corona discharges

Pulsed positive corona discharges are used to remove NO from the flue gas of a methane burner. At low power input this leads to an increase in NO₂, which shows that the process is oxidative. Removal efficiency is greatest when discharges are produced with high-voltage pulses, which are shorter in duration than the time required by the primary streamers to cross the discharge gap, in combination with a dc bias. Other important parameters are input power density and residence time. The best result obtained so far is an energy consumption of 20 eV per NO molecule removed, at 50% deNOx i.e., a removal of 150 ppm NO_x, using a residence time of 15 s and an input power density, of 3.5 Wh/Nm³. [Wh/Nm³ stands for watt-hour per normal cubic meter, i.e., at normal conditions (273 K and 1 bar). This implies that 1 Nm³ contains 2.505 10²⁵ molecules.] There appears to be room for improvement by the addition of gaseous and particulate chemicals or the use of multiple corona treatment. It is argued front comparison between results from models and experiments that the direct production of OH by the discharge is only the initiation of the cleaning process.     

金属有机配合物的非线性光学特性

从过渡金属有机配合物的中心金属、配体和几何结构的多样性、多变的金属氧化态和金属与配体的电子供－受作用评述了金属有机配合物的二阶、三阶非线性光学效应的分子结构特征和最新进展。参考文献２６篇。     

Optical emission spectroscopy as a real time diagnostic tool for plasma-assisted deposition of TiN

Real-time optical emission spectroscopy (OES) was used to monitor the deposition of TiN both from mixtures of tetrakis(dimethylamino)titanium (TDMATi)-N₂ and TiCl₄-H₂-N₂ in an electron cyclotron resonance chemical vapor deposition system. The accurate control of the ratio of the emission intensities of ionized nitrogen at 391.4 nm and molecular nitrogen at 357.7 nm (N ₂ ⁺ /N₂) led to low temperature deposition of stoichiometric TiN (Ti/N ≈ 1) and very low resistivity in both cases. It was found that high ion density plasmas are crucial for a considerable reduction of the deposition temperature while maintaining good film quality. OES shows that the abundance of certain excited plasma species is not only dependent on the gas mixture and the deposition parameters, such as total pressure and microwave power, but also is strongly affected by the magnetic field configuration. The deposition rate and the film resistivity can be related to the emission intensity ratio, I(N ₂ ⁺ )/I(N₂). Finally, the two processes are compared in terms of the quality of as-deposited and heat-treated films. The comparison shows that the films obtained with TDMATi exhibit lower resistivity and are thermally more stable than with TiCl₄.     

Optical Diagnostics of the Effect of Oxygen on Bi-Level Contact Etch

The effect of oxygen flow rate on bi-level contact etch was studied by observing uv-visible emission from the plasma, during CHF₃/CO/O₂ etching of di-electric layers consisting of SiO₂ and SiN_x. The emission intensity of CN at 387 nm drifted progressively from wafer to wafer during plasma etch. Such a phenomenon became more obvious when using low or high oxygen flow rate, whereas for intermediate flow rates, no significant drift of emission intensity was observed. The critical dimension (CD) bias of each wafer showed a strong correlation with CN emission intensity. Possible mechanisms for such an intensity drift phenomenon are proposed. The drift of emission intensity indicates that the contribution of chamber wall polymers in wafer etching is non-negligible. The CN emission intensity is an indication of the magnitude of etching rate. Our results suggest that the variation of plasma emission intensity might be used as an index for in-line monitoring of CD bias fluctuation.     

Potentiometric studies of dithiooxamide with a sulphide-selective membrane electrode

The sulphide-selective electrode is applicable to the determination of dithiooxamide by titration with silver nitrate. The effect of the alkali content of the solutions on the reaction has been studied. The reaction products are silver sulphide, oxalic acid, and nitric acid. If the alkali concentration of the solution is lower than that equivalent to the acid formed during the titration, the amount of sulphide produced by hydrolysis decreases and the equilibrium potential is established more slowly.The determination is rapid and accurate in the presence of 1 M sodium hydroxide.     

Effect of Laser-Induced Optical Breakdown on the Structure of Bsa Molecules in Aqueous Solutions: An Optical Study

The influence of laser radiation of a typical surgical laser on the physicochemical properties of the Bovine Serum Albumin (BSA) protein was studied. It was established that the physicochemical characteristics of optical breakdown weakly depend on the concentration of protein molecules. At the same time, the patterns observed for an aqueous solution of BSA irradiated with a laser for different time periods were extremely similar to the classical ones. It was established that after exposure to laser radiation, the optical density of protein solutions increases. At the same time, the intensity of BSA fluorescence due to aromatic amino acid residues decreases insignificantly after exposure to laser radiation. In this case, the position of the excitation and emission maximum does not change, and the shape of the fluorescence spot on 3D maps also does not change significantly. On the Raman spectrum after exposure to laser radiation, a significant decrease in 1570 cm⁻¹ was observed, which indicates the degradation of α-helices and, as a result, partial denaturation of BSA molecules. Partial denaturation did not significantly change the total area of protein molecules, since the refractive index of solutions did not change significantly. However, in BSA solutions, after exposure to laser radiation, the viscosity increased, and the pseudoplasticity of aqueous solutions decreased. In this case, there was no massive damage to the polypeptide chain; on the contrary, when exposed to optical breakdown, intense aggregation was observed, while aggregates with a size of 400 nm or more appeared in the solution. Thus, under the action of optical breakdown induced by laser radiation in a BSA solution, the processes of partial denaturation and aggregation prevail, aromatic amino acid residues are damaged to a lesser extent, and fragmentation of protein molecules is not observed.     

射频磁控溅射CNx薄膜的结构与衬底温度关系的研究

使用射频磁控溅射方法在不同衬底温度下（ts=室温，350，500℃）于Si(001)衬底上沉积了CNx膜，并利用拉曼（Raman)光谱、傅里叶变换红外光谱（FTIR）及X射线衍射光电子能谱（XPS）对CNx膜的化学结合状态与温度的关系进行了研究。Raman光谱结果表明，随衬底温度（ts) 增加，D带向低频方向移动，G带向高频方向移动；它们的半高宽分别由375和150cm^-1减小至328和142cm^-1；ID／IG由3．76减小至2.88。FTIR谱中除无序D带（1400cm^-1)和石墨G带（1570cm^-1)外，还有－700cm^-1,～2210cm^-1(C=N),2330cm^-1(C-O)及3255－3351cm^-1(N-H)等峰。XPS测试结果表明：随衬底温度增加，N与C的物质的量比由0.49下降至0.38，sp^2(C-N)组分与sp^3(C-N)组分强度比呈增大趋势。低温（350℃）退火并未对CNx膜的化学结合状态产生较大影响；高温（900℃）退火样品则显示出较好的结晶化程度。     

Optical Viscometry of Spinning Sol Coatings

Optical interferometric monitoring of spin coating (optospinography) has allowed close observation of the temporal evolution of a thin silicate sol film (typically at 2000 rpm, 100 Hz data acquisition). The kinematic viscosity data obtained, using a simple analytical model, are validated with those from a mineral oil standard, with agreement well within the experimental uncertainties. For spin coating in open air, the influence of variations in refractive index, rheological properties and air flow are discussed. Inflections in the temporal evolution of the optical thickness of silicate sol films are analyzed, which indicate the usefulness of optospinography, particularly when applied in the proximity of the rotation axis and evaporation is minimized, to monitor time variations in the kinematic viscosity of these sols during spin coating.     

First example of regioselective nucleophilic 1,6-addition of trimethyl(trifluoromethyl)silane to 4H-chromene derivatives

Condensation of 2-trifluoromethylchromone with diethyl malonate, ethyl cyanoacetate, and Meldrum’s acid gave the corresponding methylidene derivatives of 2-trifluoromethyl-4H-chromene. Nucleophilic 1,6-addition of an excess of Me₃SiCF₃ in the presence of Me₄NF to those obtained from the former two compounds afforded 4-substituted 2,2-bis(trifluoromethyl)-2H-chromenes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1628–1630, September, 2006.     

Optical studies of a liquid crystalline compound 6O.6

A detailed optical study for a Schiff's base liquid crystalline nO.m compound (6O.6) is reported in this article. The phase transition temperatures for the compound were investigated using a polarising microscopy and differential scanning calorimetry (DSC). Refractive index studies were conducted using the thin prism method with the 633 nm line from a He–Ne laser. The order parameters of the compound were calculated from the refractive index data. Order parameters calculated by two methods, namely, direct extrapolation method and modified Vuks’ method were found to be in close agreement. The normalised polarisabilities for extraordinary and ordinary rays and their ratio for the sample were also calculated. The order parameters are found to be reasonably high and the trend shown by normalised polarisabilities substantiates the correctness of our results. From the methods we adopted, the order parameters and the normalised polarisabilities could be determined directly from the refractive index measurements without doing the density studies. Both these methods are found to be highly suitable for the calculation of order parameters of liquid crystalline compounds having high clearing temperature where density studies are difficult and hazardous.     

Electronic Structure and Optical Properties of the Surface F-Centers in MgO: A Theoretical Analysis by DFT Approach

Electronic structure of Mg9O9 and Mg9O8 clusters modeling nano-crystalline powders of magnesium oxide has been analyzed within the frames of the density functional theory (DFT). In the framework of time-dependent DFT method (TD-DFT), the relationship between the surface and bulk properties of nano-crystals is analyzed based on variations in the density of electronic states (DOS) and changes of electronic spectra. The spectroscopy of spatial defects like low-coordinated oxygen ions and of surface point defects like F⁺- and F-centers is investigated. Optical properties of the nano-sized crystalline magnesium oxide are characterized by a spectrum of absorption bands in the range of 1-5 eV. Point defects such as F-centers absorb light in the range of 1.2-1.5 eV. Spatial defects O_LC in nano-crystals generate absorption bands in the range of 2.5-5.0 eV. According to calculations, there is no direct relation between coordination numbers of surface ions and excitation energies. Theoretical excitation energies are compared with experimental optical properties of the F⁺- and F-centers.     

Aggregation-dependence of Optical Properties and Fluorescence Quenching of a Water-soluble Poly（phenylene ethynylene）

In recent years, water-soluble conjugated polymers have been attained much attention as the optical platform in fluorescent chemical and biological sensors1. In comparison to the small molecule counterparts, conjugated polymers exhibit signal amplificatio…     

Structure-Infrared Optical Property-Correlations of C,O,H-Polymers for Transparent Insulation and Greenhouse Applications

Summary. In this paper an understanding of the physical relationships between the material structure and the temperature dependent infrared optical properties of different transparent polymer films for solar applications is described. The infrared optical properties are relevant for the heat transport of e.g. greenhouse and transparent insulation structures. The properties were determined based on infrared transmittance measurements and the assumption of a constant index of refraction from the visible range. To establish structure-property-correlations molecular structure parameters such as the concentration of carbon-oxygen single bonds and carbon-hydroxyl groups were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon-hydroxyl and the carbon-oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. This correlation fits well for high and low infrared radiation absorbing polymeric materials consisting of carbon, hydrogen, and oxygen atoms. The carbon-hydroxyl group appears to be slightly more effective than the carbon-oxygen single bond. Interestingly, the correlation works for polymers with aromatic (PC, PET) and aliphatic (PMMA, CTA, ethylene copolymers) groups.     

Molecular modeling and thermoanalytical studies of thermophysical properties of some polymers

The results of computational modeling and experimental data on some thermophysical properties of selected polymers were compared. Different engineering polymers, e.g. polycarbonates and terephthalate polyesters, were considered and their glass transition temperatures and thermal stabilities were determined, by using thermoanalytical methods, e.g. DSC and TG. Measurements were carried out with Perkin-Elmer DSC 7 and TGA 7 instruments. Molecular modeling and computer calculations were performed at the Interdisciplinary Computer Modeling Center (ICM) of Warsaw University, using a Cray El 98 computer and the Insight II software of BIOSYM Technologies Inc. Reasonably good agreement was found between the experimental and calculated values of the glass transition temperatures of the investigated polymers, e.g. for poly(butylene terephthalate)T _g (calc.)=74C andT _g (experim.)=70C. Discrepancies were observed for the temperature of half decompositionT _d,1/2, some of them can be explained by effects of polymer molecular weight and/or char-forming effects.Polymer modeling computations were performed at the Interdisciplinary Computer Modeling Center (ICM) of the Warsaw University, where a CRAY EL 98 computer and the software of BIOSYM Technologies, Inc. were used.