Ion‐beam‐induced mixing in a Si/Co/Si system involving ultrathin layers: A grazing‐incidence X‐ray standing‐wave study

Abstract

AbstractEnergetic ion‐beam‐induced mixing between Co and Si has been studied in a Si (∼5 nm)/Co (∼10 nm) bilayer system deposited on a Si (111) substrate for various ion fluences, ranging from 3 × 1014 ions/cm2 to 1 × 1015 ions/cm2. The amount of ion irradiation induced migration of Co atoms and the predominant direction of this migration (inward or outward) from the Co layer have been determined using combined X‐ray reflectivity (XRR) and X‐ray standing‐wave (XSW) techniques under grazing‐incidence conditions. Grazing‐incidence XSW technique is very sensitive for the detection of surface segregation, i.e., it would efficiently detect migration of Co toward the surface. However, in the present case ion‐beam‐induced migration of Co has been found to be predominantly inward, i.e., into the Si substrate. In this ultrathin layered system, grown under ultrahigh vacuum condition, Co has predominantly grown in a face centred cubic (fcc) – (111) orientation. In addition formation of cobalt silicide phases at the interfaces, even in the as‐prepared sample, is observed. Ion‐beam‐induced atomic mixing leads to enhanced growth of these silicide phases at the interfaces between Si and Co. However, even at the highest ion fluence in irradiation the (111)‐textured fcc Co is not fully consumed into formation of cobalt silicides.