Atomic scale study of CoSi/Si (111) and CoSi2/Si (111) interfaces

Abstract

ABSTRACT High Resolution Electron Microscopy (HREM) was used to study microstructural changes related to the CoSi/Si-CoSi/CoSi 2 /Si-CoSi 2 /Si transformations. CoSi is found to grow epitaxially on Si with [111]Si // [111]CoSi and < 110 >Si // < 112 >CoSi. Two CoSi non-equivalent orientations (rotated by 180° around the substrate normal) can occur in this plane. They can be clearly distinguished by HRTEM on cross-sections ( electron beam along [110]Si). At about 500°C CoSi transforms to CoSi 2 . Experimental results show that the type B orientation relationship satisfying [110]Si // [112]CoSi is preserved after the initial stage of CoSi 2 formation. At this stage an epitaxial CoSi/CoSi 2 /Si(111) system is obtained. The atomic scale investigation of the CoSi 2 /Si interface shows that a 7-fold coordination of the cobalt atoms is observed in both type A and type B epitaxies.