M. Drouet

Nitrogen and oxygen transport and reactions during plasma nitridation of zirconium thin films

Zirconium nitride (ZrN) is a refractory material with good mechanical and thermal properties. It is therefore a good candidate for hard surface treatment at high temperature. In this work, we report the growth and characterization of ZrN by plasma assisted thermal nitridation of zirconium films in a NH3 atmosphere. The process was monitored by in situ monochromatic ellipsometry and the nitrides grown were profiled and analyzed by Auger electron spectroscopy. By using temperatures in the 700–800 °C range, the material obtained is quite close to ZrN, but, depending on experimental conditions, residual oxygen (impurities) can be easily incorporated by reaction with zirconium. The analysis of the ellipsometric data has shown that the nitridation did not occur by simple growth of nitride on zirconium. Auger profiles confirmed the presence of an oxidized zirconium layer localized between the nitrided surface and the remaining metal. This oxidation was observed to occur preferentially during temperature ramping,...

High temperature plasma based ionic implantation of titanium alloys and silicon

Abstract Plasma based ionic implantation (PBII) of refractory materials is an alternative technique to conventional beam line implantation which appears to be very promising in the field of aeronautics, biomaterials and semiconductor electronics. In order to monitor sample temperature independently of the plasma discharge and of the pulsed high voltage conditions, we have developed a new thermally assisted PBII set-up. The thermally assisted plasma immersion implantation reactor (TAPIIR) which enables plasma implantation in the 0.5–60 keV range at controlled temperature between 200 and 1000 °C. Thermochemical treatments like nitriding of titanium and silicon were studied with a separated control of implantation and diffusion parameters. This paper describes implantations made in TAPIIR at elevated temperatures (500–900 °C) on titanium. The new results are presented and discussed by considering transport mechanisms during implantation at high temperature.

The effect of the substrate temperature on extended defects created by hydrogen implantation in germanium

H implantation in Ge was carried out at two substrate temperatures, room temperature (RT) and 150 °C. The microstructure of the as-implanted Ge samples was studied by transmission electron microscopy and grazing incidence small-angle x-ray scattering. Small (001) and {111} platelets and {113} defects are nucleated at RT. For higher substrate temperature, microcracks, cavities, and platelike cavity clusters are created as well. The formation of these types of defects is ascribed to the interplay between dynamic and kinetic effects occurring during the implantation.

A new thermally assisted, plasma based, ionic implantation system of treatment and deposition.

Abstract Plasma based ionic implantation (PBII) is a new alternative to conventional ion implantation to produce near-surface treatments, layer growth or semiconductor doping, with the advantage of being non-directional. Furthermore, it can be used for improving the corrosion, friction and wear resisting properties of materials. This paper describes the development of a thermally assisted plasma immersion implantation reactor (TAPIIR). The system aimed at treating samples in the 0.5–60 keV range, with temperature regulation up to 1000°C. Thermochemical treatments, like the nitriding of steels or aluminium, are studied with a separate implantation and diffusion parameter control.

Improved nitrogen transport in Fe–C alloys during NH3 plasma nitridation

Abstract In the thermochemical process of Fe–C alloy nitridation, improvements of mechanical properties are governed by the way the nitrogen diffusion profiles extend into the material. Up to now, thermal or ionic nitridation cannot be achieved at temperature lower than 550°C because of the strong lowering of nitrogen diffusivity. The present study shows that improved nitrogen transport can be obtained after nitridation in NH3 plasma without cathodic bias on the samples. Such cold conditions allow the iron matrix to be nitrided in a depth range of 100–400 μm at a temperature as low as 350°C. The top surface hardness was shown to be improved by a factor of 3. This surface strengthening, markedly superior to that obtained with the classical treatments, is a well-known consequence of the temperature lowering that avoids coarsening of nitride microprecipitates. In addition, using this particular process, no growth of compound layer was observed at the surface. This absence of diffusion barrier is clearly beneficial to the improvement of the nitrogen transport. The high nitridation efficiency obtained at low temperature may be explained by an enhanced grain boundary diffusion due to defects generated by hydrogenous radicals produced in the plasma.

Comparison of Defects Created by Plasma-Based Ion Implantation and Conventional Implantation of Hydrogen in Germanium

(001) n-type Ge has been implanted at given fluence and intermediate temperature with hydrogen ions using two processes: conventional in-line implantation and plasma based ion implantation. The as-created microstructure has been compared using transmission electron microscopy. In particular, it has been shown that the major differences observed are due to the implantation temperature, much higher during the PBII process. This suggests that plasma based ion implantation could be used for layer transfer in spite of a higher surface roughness observed after the PBII process.