Effect of Si layer thickness on the structural properties of a Co/Si multilayer system

Abstract

The nature of the interface involved and the structure characteristics of the as-deposited Co/Si multilayer system have been studied. Using the ionbeam sputtering technique, multilayers, having ten bilayers of Co and Si, were deposited. X-ray reflectivity, x-ray standing wave and wide-angle x-ray diffraction techniques were used to study the interface of the system. The x-ray reflectivity curves obtained confirm the good quality of the Co/Si stack. The presence of a silicide layer at the interface is not distinctly visible. The Co is found to be crystalline in nature and it is highly textured. This texture of the Co layer is lost as the Si layer thickness is increased above a particular value. We have performed some preliminary magneto-optical Kerr effect (MOKE) measurements at room temperature, which show that all the samples have ferromagnetic coupling between the different Co layers and that the nature of ferromagnetism is highly governed by the Si layer thickness.

Origin of step-like behavior in the Co/Si system

“…Here the silicide layers are too thin to exert strain on Co layers and moreover the Si layer is also very thin to exert any kind of strain on Co layers and hence Co in sample 2 is highly textured in the (002) direction. This result is consistent with our previous results [22].…”

“…Quirós et al have found the signature of AFM ordering. We, in our previous report [22], have not found any AFM coupling in Co/Si samples. Hence the origin of the variety of magnetic behaviors and the existence of an AFM coupling in the Co/Si system still remains unclear.…”

Structural and magnetic properties of CoxSi1−xthin films and multilayers

“…In particular, cobalt silicide formation has been shown to depend on the Si terrace size, on the annealing temperatures and on the relative Co/Si thicknesses [22][23][24][25][26][27][28][29]. However, other works show no clear evidence of cobalt silicide formation at Co/Si interfaces at room temperature and indicate a dependence of the Co texture on the Si layer thickness [30]. Finally, it is worth mentioning that ordered nanodots of cobalt silicide have been prepared by using polystyrene nanospheres lithography, with sizes and shapes that can be controlled by adjusting the lithography and annealing conditions [31].…”