One step multifunctional micropatterning of surfaces using asymmetric glow discharge plasma polymerization

Micropatterning of surfaces with varying chemical, physical and topographical properties usually requires a number of fabrication steps. Herein, we describe a micropatterning technique based on plasma enhanced chemical vapour deposition (PECVD) that deposits both protein resistant and protein repellent surface chemistries in a single step. The resulting multifunctional, selective surface chemistries are capable of spatially controlled protein adhesion, geometric confinement of cells and the site specific confinement of enzyme mediated peptide self-assembly.     

Substituent effects of methoxy,methyl, and vinyl groups on glow discharge polymerization

Glow discharge polymerizations in systems of trimethoxymethylsilane, trimethoxyvinylsilane, tetramethylsilane, and trimethylvinylsilane were compared by elemental analysis, infrared (IR) spectroscopy, and ESCA to reveal effects of methoxyl, methyl, and vinyl substituents. The substituent effects appeared in the chemical composition of the polymers formed especially at low W/FM values. Methoxy groups depressed the C/Si and H/Si ratios of the polymers rather than the methyl groups, whereas vinyl groups increased the C/Si and H/Si ratios. On IR spectra the polymers formed from silanes that contained methoxy groups showed fewer absorptions due to Si? H groups and strong absorptions due to Si? OH groups. The polymers from those that contained no methoxy groups showed absorptions of Si? H groups and no absorptions of Si? OH groups. These differences in the environment of Si atoms of polymeric chains also appeared in the Si_2p core level spectra, thus indicating the different fragmentation patterns of the starting materials in glow discharge.     

Powering the analytical glow discharge

The glow discharge may be powered by direct current (dc), radio frequency (rf) and pulsed discharge sources. Each has specific advantages and special features that should be considered by analysts using the various forms of glow discharge spectroscopy. This paper reviews some of the factors that contribute to the selection of a power source for the glow discharge.     

Microsecond-pulse glow discharge atomic emission

A microsecond pulsed glow discharge was produced with high pulse magnitude and small duty cycle. Time resolved emission and absorption spectroscopy was applied to study the processes of atomization, excitation and ionization in the glow discharge. Experimental results show that, without overheating the sample, the emission peak intensity is several orders greater than that obtained in the conventional dc mode. This implies that a much more intense plasma is generated during pulsed "on" region.     

Microsecond-pulse glow discharge atomic emission

A microsecond pulsed glow discharge was produced with high pulse magnitude and small duty cycle. Time resolved emission and absorption spectroscopy was applied to study the processes of atomization, excitation and ionization in the glow discharge. Experimental results show that, without overheating the sample, the emission peak intensity is several orders greater than that obtained in the conventional dc mode. This implies that a much more intense plasma is generated during pulsed on region.     

Powering the analytical glow discharge

The glow discharge may be powered by direct current (dc), radio frequency (rf) and pulsed discharge sources. Each has specific advantages and special features that should be considered by analysts using the various forms of glow discharge spectroscopy. This paper reviews some of the factors that contribute to the selection of a power source for the glow discharge.     

Analytical glow discharge mass spectrometry

Various types of glow discharge mass spectrometric systems as well as their applications are considered. Special attention is paid to radiofrequency and pulsed glow discharges combined with time-of-flight mass spectrometers. Along with typical application fields of glow discharge mass spectrometry, analysis of semiconductors, polymers, and dielectrics, as well as isotope analysis and depth profiling are also reviewed. Some methods of standard-free mass spectrometric analysis of solids are considered. Prospects for combining glow discharge mass spectrometry with preliminary chromatographic separation are discussed.     

辉光放电质谱技术应用进展

对辉光放电质谱(GDMS)在金属与半导体、非导体、薄层与深度分析、分子信息分析方面的应用和一些新装置、新方法进行了综述.着重介绍了近20年来我国学者在辉光放电质谱方面的成就,并结合国际上的报道对该领域的发展现状进行了总结.     

Spatial and temporal studies of a glow discharge

A demountable glow discharge tube was constructed with the objective of studying the various processes taking place in the discharge and resolving these both spatially and temporally. Argon and neon were used as fill gases. Continuous wave laser excited fluorescence was used to study the spatial distribution of sodium atoms which were sputtered off the cathode; a value for the diffusion coefficient of sodium in argon was obtained from time-resolving these experiments. From the population ratios of the various excited levels which we observed, we conclude that no single excitation temperature predominates anywhere between the electrodes under our conditions; instead, several population inversions were observed. Emission intensities of lines from atoms and ions were resolved as a function of the axial position between the electrodes. A temporal region was found where the signal-to-noise ratio for the detection of small quantities of analytes may be optimized. In addition to numerous atomic lines from the fill gas, we also detected fill gas ions as well as Fe, Fe⁺ and Cr when using stainless steel as a sample.     

Guiding DC glow discharge in microchannels

This work describes the conditions, in terms of dimensions and geometry, to guide a dc glow discharge preferentially through a microchannel in simple networks. Two- and three-channel microfluidic structures were studied. A preference towards a wider channel, in a two-channel network, was observed when the difference in width was at least 18% and the length was at least 10 mm. In a three-channel structure, a change in glow discharge intensity was observed when the network was downscaled from a pathlength of 2 to 0.5 cm. While the intensity within the path with fewer turns decreased with a reduction in size, the intensity of the path with greater number of turns increased.     

Comparative studies on excitation of nickel ionic lines between argon and krypton glow discharge plasmas

The emission characteristics of nickel ionic lines in a glow discharge plasma are investigated when argon or krypton was employed as the plasma gas. Large difference in the relative intensities of nickel ionic lines which are assigned to the 3d⁸4p–3d⁸4s transition is observed between the krypton plasma and the argon plasma. Different intense Ni II lines appear in the krypton spectrum and in the argon spectrum, such as the Ni II 231.601 nm for Kr and the Ni II 230.009 nm for Ar. The excitation energy of these Ni II emission lines can give a key in considering their excitation mechanisms. The explanation for these experimental results is that charge-transfer collisions between nickel atom and the plasma gas ion play a major role in exciting the 3d⁸4p excited levels of nickel ion. The conditions for energy resonance in the charge-transfer collision determine particular energy levels having much larger population; for example, the 3d⁸4p ⁴D_7/2 level (6.39 eV) for Kr and the 3d⁸4p ⁴P_5/2 level (8.25 eV) for Ar.     

Non-flat surfaces analysis by glow discharge spectrometry

A glow discharge system is developed which allows to evaluate concentration profiles directly on the external surface of tubes while keeping a good resolution in depth, avoiding the flattening of tubes which can lead to cracks and deformation of the surface oxide layer. The geometry and the operating parameters of the device have been optimized for the characterization of Zircaloy 4 tubes used to manufacture a pressurized-water reactor fuel assembly. The principle of that modification can be extended to tubes with other geometries by adjusting the semicircular slit to the diameter of the tube to be analyzed.     

Fundamental aspects and applications of glow discharge spectrometric techniques

Glow discharges are kind of plasmas which are used in many fields of application, including analytical spectrometry. This review addresses both the fundamental aspects and analytical applications of glow discharges. In the first part, a systematic overview of the most important plasma processes is presented. To obtain better insight into the complexity of the glow discharge, both mathematical modeling and experimental plasma diagnostics can be carried out. Therefore, the models that were developed for a glow discharge are presented and typical results (e.g. three-dimensional density profiles, fluxes and energy distributions of the various plasma species, the electric field and potential distributions, information about collision processes in the plasma and about sputtering at the cathode, etc.) are summarized. Moreover, the most important plasma diagnostic techniques for glow discharges are discussed. In the second part, an overview is given of the various analytical applications of glow discharges.     

Film deposition in a radial flow reactor by plasma polymerization of hexamethyldisilazane

Polymeric substrates can be coated at low temperatures by means of an electric discharge fed by organic gases. Since both the composition and the structure of the deposited material can be varied in a wide range by the choice of starting compound and deposition conditions, the properties of the coatings can be adjusted specifically to fulfill many required demands. After a general introduction of the deposition method, a typical deposition apparatus is described and an optimization procedure of the deposition process is proposed.The intermediate position of plasma polymerized materials between common polymers and amorphous solids is demonstrated for films from hexamethyldisilazane. Based on the assumption of a continuous random network structure the density of covalent bonds and the total volume fraction of micro-voids can be evaluated and compared with application relevant properties such as mechanical stiffness and gas permeability.The model of a continuous random network structure may be valid for plasma polymerized material in general.     

Non-flat surfaces analysis by glow discharge spectrometry

A glow discharge system is developed which allows to evaluate concentration profiles directly on the external surface of tubes while keeping a good resolution in depth, avoiding the flattening of tubes which can lead to cracks and deformation of the surface oxide layer. The geometry and the operating parameters of the device have been optimized for the characterization of Zircaloy 4 tubes used to manufacture a pressurized-water reactor fuel assembly. The principle of that modification can be extended to tubes with other geometries by adjusting the semicircular slit to the diameter of the tube to be analyzed.     

Microsecond pulsed glow discharge time-of-flight mass spectrometer

A linear time-of-flight mass spectrometer (TOFMS) has been designed, constructed, and coupled with a glow discharge source in microsecond pulsed mode (MSPGD). Orthogonal acceleration, a DC quadrupole and deflecting pulse techniques are used to diminish kinetic distribution and the spatial distribution of ions, and for deflecting Ar⁺ ions in their flight path. Comparison was made in the same discharge source between MSPGD and DC discharge. The continuous ion current is only 0.2 nA in the DC discharge mode, while the peak ion current reaches over 100 nA in the MSPGD mode. In addition, the ratio of the repelled ions to total ions is much higher in MSPGD than with a DC discharge in TOFMS. The mechanism of MSPGD is discussed. A resolving power of 500 was achieved, which is excellent for elemental analysis. To the authors' knowledge, this is the first time that a MSPGD-TOFMS combination has been described. The system is now being further optimized to improve its performance.