Oscillating composition of Fe–W alloy thin films grown by magnetron co-sputtering

Fe–W alloy coatings were deposited by D.C. magnetron co-sputtering at room temperature. Initial results from Rutherford Backscattering Spectroscopy (RBS) have evidenced in-depth variation in the film chemical composition, which oscillates between Fe0.19W0.81 and Fe0.29W0.71. The deposits are multilayer systems composed of elementary alloy layers, with a thickness of the order of several tens of nanometers. In the present work, we study the influence of two deposition parameters on this particular in-depth composition modulation: substrate rotation rate and deposition time. The thickness of the elementary layers depends on the rotation rate of the substrate holder, as expected from what is reported in the literature on pure nanolayer synthesis in planar magnetron geometry. Surprisingly, the composition oscillations disappear for the longest deposition times (above 3 min). Alloy films (with or without composition oscillations) are found to exhibit the same morphology and crystalline structure as pure W. It is evidenced that Fe atoms are located in substitution in the W atomic structure and that an amorphous phase of alloy is also formed.