Morphology of cobalt layers on native SiO2 surfaces at elevated temperatures: Formation of Co islands

The influence of deposition and annealing temperature on the morphology of ultra-thin cobalt layers on the native SiO2 surfaces has been investigated using AFM and XPS. To provide well defined conditions, the SiO2 layer was cleaned by thermal annealing at 560-580 °C which caused desorption of the carbonaceous compounds. The deposition of Co on the native SiO2 at room temperature leads to the formation of smooth uniform layers. Upon annealing of these layers at temperatures above 260-320 °C Co islands are formed. Further annealing at temperatures higher than 500 °C causes desorption of Co atoms from the oxide surface. No diffusion of Co atoms through the native SiO2 layer during the annealing has been observed up to the detection limit of XPS. The deposition at elevated temperatures in the range of 360-430 °C leads to the formation of separate cobalt islands randomly arranged on the surface.