Ion Extraction of Cl Containing Plasmas — Problems and Possibilities of the Investigations of Plasma Processes

The ion extraction is investigated from Cl₂-, SiCl₄- and CCl₄-plasmas within a planer-reactor in dependence on pressure and power density. Furthermore the relative ion formation cross sections of the ions fragments of these gases are measured versus the electron energy within a mass spectrometer tube. It will be concluded the decomposition of these gases from the measured ratios of the extracted currents of single ions in dependence on the plasma parameters. The extracted ion spectra extrapolated to a low degree of decomposition are compared with the ion fragments formed by electron impact within the mass spectrometer tube and thereby the effective electron energy in the plasma sheath nearby the orifice estimated.     

The effect of the ionization gauge on the composition of residual gases

The present work deals with the study of changes in the composition of residual gases caused by the action of an attached nude ionization gauge in an all-metal ultra-high vacuum system with an oil free pumping unit. The mass spectra of residual gases obtained when the ionization gauge was switched off and when it worked in two different operating modes are presented. They form a basis for the discussion of processes which take place in the ionization gauge and of their influence on the composition of residual gases. Some practical consequences of the studied effects for the measurement of very low pressures are discussed in the present paper.     

Analysis of solids by secondary ion and sputtered neutral mass spectrometry

A mass spectrometer is described, which allows the analysis of sputtered neutral and charged particles as well as of residual gas composition. This combined SIMS, SNMS, and RGA instrument consists of a scanning primary ion beam column, an electron impact ionizer, an electrostatic energy filter and an rf quadrupole mass analyzer.Various examples of surface and bulk analysis are presented which demonstrate the beneficial complementary features of these techniques. These are, in particular: a substantial reduction of the matrix effect and fewer complications with samples of low electrical conductivity in SNMS, and the possibility of measuring the depth distribution of gases included in small cavities in the solid in the SNMS/RGA mode. SIMS, on the other hand, allows in many cases higher detection sensitivities.EURATOM Association     

ToF atom-probe fim study of LaB6 single crystals

The field evaporation mass spectra of LaB₆ are obtained with time-of-flight atom-probe field ion microscope in vacuum and in the presence of hydrogen, nitrogen and oxygen. The spectra are consistent with a preferential chemisorption of these gases on boron sites.     

Mechanisms of oxidation-reduction processes on metal and oxide surfaces under ion bombardment

Surface oxidation occurs if metals are bombarded with low-energy (1–5 keV) ions of a chemically active gas (oxygen) in vacuum. It is ascertained that ion bombardment leads to the generation of lower, intermediate, and higher oxides. The composition and thickness of an oxidized layer depend on the metal reactivity and the dose and energy of oxygen ions. The mechanism underlying the ion-beam oxidation of metal surfaces is proposed. Surface reduction is observed if higher oxides are bombarded with low-energy (1–5 keV) ions of inert gases (argon and helium) in vacuum. It is revealed that ion bombardment not only generates intermediate and higher oxides but sometimes gives rise to surface metallization. The composition and thickness of the reduced layer are determined by the oxide type, the kind of inert gases, and the dose and energy of bombardment. The mechanism describing the ion-beam reduction of higher metal oxide surfaces is proposed.     

Experimental study of isotope scaling of ion thermal transport

The wide divergence between most theoretical predictions of isotopic mass scaling of transport and tokamak experimental results motivated a basic physics experiment in the Columbia Linear Machine [R. Scarmozzino, A. K. Sen, and G. A. Navratil, Phys. Rev. Lett. 57, 1729 (1986)]]. The experiments on ion thermal conductivity due to ion temperature gradient-driven slab modes are performed using two different gases: hydrogen and deuterium. The results indicate inverse dependence of ion thermal conductivity on the isotope mass close to K(radially) approximately A(-0.5)(i). This is similar to the tokamak results, but in stark contradiction to most present theoretical models.     

Ionization by low energy heavy ions in nitrogen,carbon dioxide,argon and hydrocarbon gases

Experimental data on the variation of W, the mean energy expended by a charge particle in producing an ion pair in a gas, with the mass, charge and energy of the particle is examined with a view to discovering how far these variations may be explained in terms of elastic nuclear scattering. In nitrogen and carbon dioxide W appears to depend not only on the elastic nuclear scattering but also on the parameter E/MZ^4/3 for ions other than piotons. In argon any relationship is obscured by apparent discrepancies in the data, although it is possible that the variation may be similar to that in nitrogen and carbon dioxide. The data for the hydrocarbon gases is not so extensive as for the other gases and it may be that the variation of W with the mass and charge of the ion is different from that in nitrogen and carbon dioxide. It is speculated that this difference, if real, is due to super-excited states in the hydrocarbon gases.

Some empirical relationships are suggested as a practical guide for use in dosimetry.     

Laser pyrolysis of coal

A laser pyrolysis study was performed on No. 6 high volatile bituminous Illinois (USA) coal. Possible relationships between the elemental surface composition of solid samples and the variable output power and wavelength of the argon ion laser were observed. For wavelengths of 5017 Å and 5145 Å and incident powers of 0·24 and 0·54 watts, scanning electron microscopy coupled with X-ray energy spectral analysis indicated the highest content reduction in both organic and mineral sulfur.Mass spectroscopy was employed to analyze the composition of the evolved gases from laser pyrolysis of pulverized coal. Coal pyrolysis utilizing a 2·5 watt argon ion laser produced hydrogen sulfide through decomposition of pyritic sulfur FeS₂, or organic sulfur upon irradiation of the coal. Other gases such as methane and ethane were created with solid residues (tars and ash). Pulsed CO₂ laser irradiation of coal samples produced a solid residue having a different elemental composition than that of the original coal sample.     

Effect of the isotope composition and unsaturated bonds on the mass defect spectrum of residual hydrocarbons

By accurately measuring the position of the peaks in the ion mass spectrum of residual gases, it is found that the peaks are associated with hydrocarbon ions. The “mass defect” spectrum is close to that obtained analytically. The deviations observed are related to the presence of the ¹³C isotope and nonsaturation of bonds in the ions recorded. The experimental data obtained may be used as a reference in impurity microanalysis, in calibrating the mass scale of mass spectrometers, and in checking the theory of mass spectrum analysis.     

Residual gas properties in a field emission device with ZnO emitters

In this paper, a vacuum system is employed to compare the emission stabilities of the same ZnO cathode in a sealed field emission （FE） device and under ultrahigh vacuum （UHV） conditions. It is observed that the emission current is more stable under the UHV level than in the device. When all conditions except the ambient gases are kept unchanged, the emission current degradation is mainly caused by the residual gases in the sealed device. The quadrupole mass spectrometer （QMS） equipped on the vacuum system is used to investigate the residual gas components. Based on the obtained QMS data, the following conclusions can be drawn： the residual gases in ZnO-FE devices are H2, CH4, CO, Ar, and CO2. These residual gases can change the work function at the surface through adsorption or ion bombardment, thereby degrading the emission current of the cathode.     

三代像增强器用微通道板的改进与发展

简要说明了三代像增强器的特点，分析了微通道板的离子反馈形成机理，给出有效抑制离子反馈对光阴极造成伤害的2种方法，即一种是减少和清除微通道板的吸附气体，另一种是阻止反馈离子反馈到光阴极上。介绍了国外最新的三代像增强器，以及使用优化改进的高性能微通道板显著减薄甚至彻底去除微通道板离子反馈膜的方法，该方法能维持砷化镓光阴极足够长的工作寿命，还介绍了最新发展的体导电微通道板和硅微通道板。指出高可靠性无膜选通砷化镓像增强器技术的实现，不仅需要微通道板在抑制离子反馈方面取得突破，还需要砷化镓光阴极在耐受离子反馈能力上进一步提高，同时还要结合和拓展选通电源的应用。     

三代微光管防离子反馈Ａｌ２Ｏ３ 膜电子轰击放气成分分析

为了解决防离子反馈Ａｌ２Ｏ３膜污染对三代微光管ＧａＡｓ光电阴极灵敏度的影响,用四级质谱计对制管超高真空室残气、无膜微通道板（ＭＣＰ）和带Ａｌ２Ｏ３膜ＭＣＰ在电子轰击时的放气成份进行分析。结果表明,带Ａｌ２Ｏ３膜ＭＣＰ放出有对阴极光电发射有害的Ｃ、ＣＯ、ＣＯ２、ＮＯ、Ｈ２Ｏ２和ＣXＨY化合物,它们来源于Ａｌ２Ｏ３膜制备过程的质量污染。经过对制膜工艺质量进行改进,制备出了放气量小于２１０－９ Ｐａ且无ＣＸＨＹ化合物气体的Ａｌ２Ｏ３膜。     

The energy distribution of an ion in a radiofrequency trap interacting with a nonuniform neutral buffer gas

An ion in a radiofrequency (rf) trap sympathetically cooled by a simultaneously trapped neutral buffer gas exhibits deviations from thermal statistics caused by collision-induced coupling of the rf field to the ion motion. For a uniform density distribution of the buffer gas, the energy distribution of the ion can be described by Tsallis statistics. Moreover, runaway heating of the ion occurs if the buffer gas particles are sufficiently heavy relative to the ion. In typical experiments, however, ultracold buffer gases are confined in traps resulting in localised, non-uniform density distributions. Using a superstatistical approach, we develop an analytical model for an ion interacting with a localised buffer gas. We demonstrate theoretically that limiting collisions to the centre of the ion trap enables cooling at far greater mass ratios than achievable using a uniform buffer gas, but that an upper limit to the usable mass ratio exists even in this case. Furthermore, we analytically derive the functional form of the energy distribution for an ion interacting with a buffer gas held in a harmonic potential. The analytical distribution obtained is found to be in excellent agreement with the results of numerical simulations.     

Isotope effects induced by the action of ions on the surface of solids

We report on the results of study of isotope effects induced in solids by ion sputtering and ion implantation. The experiments are carried out using secondary ion mass spectrometry and secondary ion energy-mass spectrometry on molybdenum and copper-implanted nickel samples, as well as a number of titanium modifications. General regularities are revealed in the variation of the isotope composition in various processes. The mechanisms of isotope effects are discussed.     

The properties of the nonequilibrium LaB6 surface resulting from field evaporation

The nonequilibrium surface of single-crystal lanthanum hexaboride needles and its modifications are studied with a time-of-flight atomic probe. The surface is obtained by room-temperature field evaporation. The mass spectra of field evaporation shed light on the surface composition at the needle tip immediately after tip etching, corrosion in residual gases, intense cleaning by field evaporation, and the relaxation of the nonequilibrium surface by heating to 1250 K. Conditions for the breakdown of an oxide film on the tip surface and for obtaining the mass spectra of field evaporation for stoichiometric or lanthanum-enriched pure LaB₆ single crystals are discussed.     

Hydrogen induced voids in hydrogenated amorphous silicon carbon (a-SiC:H): Results of effusion and diffusion studies

The void formation in Si-rich a-SiC:H films deposited with dc magnetron sputtering is studied by effusion measurements of hydrogen and of implanted rare gases and secondary ion mass spectrometry (SIMS). Rare gas atoms were incorporated into the material by ion implantation. The results suggest a widening of the network openings with increasing alloy concentration. However, the void formation is mainly attributed not to an increase in carbon concentration but to an increase in hydrogen incorporation.     

Phase theory for binary one-dimensional Fermi gases in harmonic traps

The phase theory of two interacting one-dimensional degenerate Fermi gases confined to different harmonic traps is developed based on the concept of bosonization. The excitation spectra of mass and composition waves are calculated and stability boundaries as function of interaction strength and frequency detuning of the traps are found. The experimentally accessible non-local mobilities and their relation to the excitation frequencies are also studied. The problem of the Kohn mode within phase theory is discussed and a solution is proposed. As an example of the simplicity and effectiveness of the new approach the propagation of a composition perturbation across the Fermi seas is calculated analytically.     

Effects of ion sputtering on semiconductor surfaces

Ion beam sputtering has been combined with Auger spectroscopy to study the effects of ion beams on semiconductor surfaces. Observations on the mass dependence of ion selective sputtering of two component systems are presented. The effects of ion implantation are explained in terms of atomic dilution. Experimental data are presented that illustrate the superposition of selective sputtering and implantation effects on the surface composition. Sample reduction from electron and ion beam interaction is illustrated. Apparent sample changes which one might observe from the effects of residual gas contamination and electric fields are also discussed.     

Spectral characteristics of a dense gas-metal reflection discharge plasma

Elemental composition of the plasma, which mostly includes working substances introduced into the discharge through puffing of hydrogen and sputtering of titanium, is determined by the spectrometric method. The analysis of the spectrum of microwave signal fluctuations shows that the characteristic spectrum peaks correspond to ion cyclotron frequencies of the gases and metal vapors forming the atmosphere of the discharge. The characteristic peaks of the optical and microwave discharge fluctuation spectra are found to coincide.     

Confined direct analysis in real time ion source and its applications in analysis of volatile organic compounds of Citrus limon (lemon) and Allium cepa (onion)

The DART (direct analysis in real time) ion source is a novel atmospheric pressure ionization technique that enables efficient ionization of gases, liquids and solids with high throughput. A major limit to its wider application in the analysis of gases is its poor detection sensitivity caused by open-air sampling. In this study, a confined interface between the DART ion source outlet and mass spectrometer sampling orifice was developed, where the plasma generated by the atmospheric pressure glow discharge collides and ionizes gas-phase molecules in a Tee-shaped flow tube instead of in open air. It leads to significant increase of collision reaction probability between high energy metastable molecules and analytes. The experimental results show that the ionization efficiency was increased at least by two orders of magnitude. This technique was then applied in the real time analysis of volatile organic compounds (VOCs) of Citrus Limon (lemon) and wounded Allium Cepa (onion). The confined DART ion source was proved to be a powerful tool for the studies of plant metabolomics.