The Co/Si(111) interface formation: a temperature dependent reaction

We have investigated the reaction of Co with the Si(111) surface both at room temperature (RT) and at high temperature (500-650 degreesC). The temperature evolution of the RT deposited 10 ML film has also been studied. The films, prepared by the different methods, have been structurally characterized by means of primary-beam diffraction modulated electron emission. Auger electron spectroscopy has been used to follow their stoichiometric evolution. For RT deposition the films have been found to have a B-type (180degrees rotated with respect to the underlying Si(111) surface) cubic structure with a Co content and an interlayer spacing increasing with thickness. After 650 degreesC annealing, the films are completely reacted and have an unstrained B-type CoSi2 structure. High temperature (500 degreesC) deposition of Co leads to the formation of stoichiometric CoSi2 films. Both annealed and high temperature grown films are found to be Si terminated.