In situ stress measurements during the growth at different temperatures of Ag–Cu(111) multilayers

Abstract

We studied, at different temperatures, the stress development during the growth of Ag–Cu(111) multilayers. Multilayers, with a nanometric period, were UHV evaporated on Si(111) and stress was monitored in situ by measuring substrate bending. We show that whatever the evaporation temperature may be, the Ag on Cu(111) growth does not develop any representative stress. This quasi-unstressed Ag on Cu(111) growth could be consistent with an intrinsic relaxation resulting from a strong atomic reorganization during early stage (1 monolayer deposited) of interface formation. On the contrary, the Cu on Ag(111) growth develops a temperature-dependent tensile stress. The measured stress at room temperature is 1 GPa and decreases to 0.5 GPa at 110 °C for a 3 nm deposited thickness. This temperature-dependent stress could be related to a weak three-dimensional temperature-dependent growth mode during an early stage of film deposition. Our results also indicate, at 35 °C, a clear stress relaxation for thickness larger than 3 nm, while no relaxation is observed at 110 °C. We show that the Matthews–Blakeslee model is not adequate to describe this relaxation.