Effects of Ge Overlayers on the Formation of Nickel Disilicide
The effects of Ge overlayers on the reaction of one monolayer of Ni on Si(001) substrate were investigated. The samples were then ex situ annealed at 400 to 800°C. The reaction process began with dissolution of the Ni atoms into the amorphous Ge layer. Then, solid-phase epitaxy of the amorphous layer was observed. The Ni atoms were expelled from the crystallized region and redistributed in the amorphous region. Until the concentration of Ni in the amorphous Ge layer exceeded the solubility limit, the Ni atoms diffused through the crystallized Ge layer and reacted with the substrate to form NiSi 2 . The NiSi 3 phase formation was kinetically controlled by the rate of solid-phase epitaxy of the Ge overlayers for the reaction system.
Abstract Many human operations have created a large population of small orbital debris in near Earth environment. The threat they represent for satellites is a major factor for the preparation of future space missions. Several experiments devoted to the study of this environment, as well as various materials exposed to space, have been retrieved in the past few years. The analysis of the results shows some differences with previous modeling. Comparison with data from LDEF and from EURECA give some insight in the long term evolution of particle size distribution. Chemical identification of particle remnants inside craters is difficult but provides valuable information on the origin of the impactors. Permanent monitoring of environment is obviously needed, especially for the type of orbits where data are presently scarce ie. heliosynchronous and geostationary orbits.