Structure evolution in Ag/Ni multilayers grown by ultra high vacuum DC magnetron sputtering

Ag/Ni multilayers have been grown by ultra high vacuum d.c. magnetron sputt ering onto oxidized Si(001) substrates held at room temperature. Films were grown in both Ar and Kr discharges at different sputtering pressures p. Th e effects of the different discharge pressures and post-deposition annealin g were investigated. The structure evolution was studied using atomic force microscopy (AFM), X-ray diffraction (XRD) and transmission electron micros copy (TEM). XRD pole figure analysis show that all films exhibit a pronounc ed [111] fiber texture. Sputtering using low pressures resulted in a reduct ion of the surface roughness, compared to films grown at higher pressures, and films with rms roughness values as low as 1-2 nm were obtained. XRD ana lysis show that also the definition of the layer interfaces and the crystal linity of the films improved when the pressure was lowered and when using A r instead of Kr. The increase in surface roughness with discharge pressure is explained by a reduced adatom mobility on the growing film surface at hi gher pressures and a wider range of incidence angles of the adatoms when ar riving at the surface due to gas scattering. The improved crystalline quali ty when using Ar instead of Kr is explained using similar arguments. Short post-deposition annealing at 280 degrees C resulted in improved layer defin itions as well as improved intralayer order whereas prolonged annealing or annealing at 390 degrees C resulted in agglomeration of Ag precipitates and loss of the compositional modulation. A qualitative model based on the imm iscibility of the Ag-Ni system and different diffusivities of Ag and Ni, is proposed. (C) 1999 Elsevier Science S.A. All rights reserved.