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Plasma-immersion doping, a technique more compatible with the processing of large-area glass substrates, is investigated as a replacement of ion implantation for incorporating fluorine in a zinc oxide thin film to improve the electrical characteristics of the corresponding thin-film transistors. Since the average energy of the ions in a plasma is lower than that of the ions used for implantation, less damage is induced in the channel of a transistor by the bombardment of the ions. Consequently, enhancement-mode transistors with a relatively high field-effect mobility of similar to 71 cm(2)/V.s, a lower drain leakage current, and improved reliability have been realized.

There is no doubt that lead (and its alloys with tin) and brass materials do not really belong to the stuff of primary interest for advanced materials studies. Also, lead gets more and more removed from the technology of soldering in electronics etc., and brass is, at least, a material of doubtful character if treated in vacuum. On the other hand these metals are of primary interest for the construction of pipe organs, and that already for millenia! Corrosion of lead and brass are a serious obstacle in old and even new pipe organs if the microclimate inside of the organ, the church, the concert hall etc. is containing special residuals or impurities leading to the growth of corrosive layers. Finally, even holes can be “drilled” into metal pipes making them voiceless! For this end we have started to fight with this problem by using nanotechnology to cover metallic sheets of lead and brass with thin layers of anticorrosive material. Plasma immersion ion implantation of nitrogen was used to keep the technology simple and to have certain intermixed interface layers between the surface and the substrate. AES and XPS demonstrated surface layers with a thickness in the range below 50 nm. The exact composition and mechanism is a matter of discussion yet. Laboratory-based corrosion studies were developed and applied to the plasma-treated surfaces. First results were quite promising and showed strong corrosion resistance, especially for lead. Field studies at historical organs in Saxony and Mecklenburg are ongoing.

Plasma immersion ion implantation (PIII) from a chlorine containing plasma has been used in order to improve the high temperature oxidation behavior of titanium aluminide alloys. This process is promising since the subsurface Cl concentration, which is needed for optimum protection against oxidation, can be quickly obtained (approx. fluence 1·1016 Cl/cm-2) in a PIII process. A PIII system being resistant against the strongly etching Cl2 plasma is presented. Plasma diagnostics of the Cl2 plasma sustained by an ICP source using Langmuir probe measurements is discussed. For the electro-negative Cl plasma, the measurements are examined regarding the influence of negative ions. The implantation of Cl is correlated to the plasma parameters using AES depth profiling of the surface after implantation. The high temperature oxidation behavior is tested using thermogravimetrical analysis (TGA) in air at 900 °C and microstructural investigations of the oxide scale. PIII implantations of Cl2 with 30 kV HV pulses (effective energy 15 keV) show a strong reduction of the oxidation at 900 °C in air, which is comparable to conventional beam line im-plantations of Cl at 15 keV.

Model experiments with low-energy ions under controlled vacuum conditions have been performed in order to identify the surface processes and the diffusion mechanism associated with the nitrogen transport during ion nitriding of stainless steel 316 and pure aluminium. A necessary condition for an efficient nitriding is the transmission of the implanted ions through a surface oxide layer which results from a balance of ion sputtering and re-oxidation from the residual gas. For ion energies around 1 keV and ion current densities around 0.2 mA/cm2, oxygen partial pressures of less than about 3A10-6 mbar and 3A10-7 mbar are required for stainless steel and aluminium, respectively. Diffusion under the influence of traps controls the transport of nitrogen in stainless steel, with dynamic trapping at the Cr atoms of the alloy. In contrast, stoichiometric AlN grows on aluminium due to Al diffusion from the underlying bulk. From the surface and diffusion mechanisms, limitations of plasma nitriding and plasma immersion ion nitriding are derived, and the implications for industrial applications are discussed.

WCx coatings have been synthesized by filtered cathodic arc deposition at room temperature. Repetitively pulsed W and C plasma streams were mixed, and the duration of the pulse of each stream was used to vary the film composition. The energy of the incident ions was controlled by applying a pulsed bias voltage at the substrate, and was used for enhancing the adhesion as well as for modifying the microstructure of the film. The films with low W content (less than 20 at.%) consisted of regions of amorphous WC dispersed in an amorphous carbon matrix. At higher W content, nano-crystalline WC was observed. Internal stresses in the as deposited films ranged between 500 and 4500 MPa, depending on the W content and the applied bias voltage. Film hardness varied between 63 GPa and 30 GPa, and strongly depended on the W content and also on the applied bias voltage. © 1997 Elsevier Science S.A., SCOPUS: ar.j, info:eu-repo/semantics/published