Vacuum 

Abstract: Methods for determining the activation energy, rate constant and order of reaction from “flash-filament” desorption experiments are examined. Two heating schedules are considered: (a) a linear variation of sample temperature with time (T = T0+st), and (b) a reciprocal temperature variation ( 1 T = 1 T 0 −αt) . The activation energy of desorption is estimated from the temperature (Tp) at which the desorption rate is a maximum (for first-order reactions) and from the change of Tp with surface coverage (for second-order reactions). The order of the reaction is determined from the shape of the desorption rate versus time curve, or the variation of Tp with coverage. Applications of these methods to experiments on chemisorption and the desorption of ionically trapped gases are discussed. The effect of finite pumping speed in the system is analysed and the necessary corrections derived.

Abstract: Magnetron sputtering has become the process of choice for the deposition of a wide range of industrially important coatings. Examples include hard, wear-resistant coatings, low friction coatings, corrosion resistant coatings, decorative coatings and coatings with specific optical, or electrical properties. Although the basic sputtering process has been known and used for many years, it is the development of the unbalanced magnetron and its incorporation into multi-source `closed-field’ systems that have been responsible for the rise in importance of this technique. Closed-field unbalanced magnetron sputtering (CFUBMS) is an exceptionally versatile technique for the deposition of high-quality, well-adhered films. The development, fundamental principles and applications of the CFUBMS process are, therefore, discussed in some detail in this review. Also discussed are other important recent developments in this area, including the pulsed magnetron sputtering process, variable field magnetrons, and the combining of sputtering techniques with other surface coating, or surface modification techniques in duplex production processes.

Abstract: Barrier discharges (BDs) produce highly non-equilibrium plasmas in a controllable way at atmospheric pressure, and at moderate gas temperature. They provide the effective generation of atoms, radicals and excited species by energetic electrons. In the case of operation in noble gases (or noble gas/halogen gas mixtures), they are sources of an intensive UV and VUV excimer radiation. There are two different modes of BDs. Generally they are operated in the filamentary one. Under special conditions, a diffuse mode can be generated. Their physical properties are discussed, and the main electric parameters, necessary for the controlled BD operation, are listed. Recent results on spatially and temporally resolved spectroscopic investigations by cross-correlation technique are presented. BDs are applied for a long time in the wide field of plasma treatment and layer deposition. An overview on these applications is given. Selected representative examples are outlined in more detail. In particular, the surface treatment by filamentary and diffuse BDs, and the VUV catalyzed deposition of metallic layers are discussed. BDs have a great flexibility with respect to their geometrical shape, working gas mixture and operation parameters. Generally, the scaling-up to large dimensions is of no problem. The possibility to treat or coat surfaces at low gas temperature and pressures close to atmospheric once is an important advantage for their application.

Abstract: The relative sensitivities of a Bayard-Alpert ionization gauge for various organic molecules have been measured. There is a good correlation with total ionization cross section at 75 eV. For monofunctional compounds a correlation with number of electrons is seen with different functional groups on different lines. The best general correlation is with the polarizability, α, with R x =0.36 α +0.30, where R x is the chemical sensitivity relative to N 2 =1.00. Alkanes and the noble gases have slightly larger R x values than predicted by this equation.