Structural control in porous/compact multilayer systems grown by magnetron sputtering

In this work we analyze a phenomenon that takes place when growing magnetron sputtered porous/compact multilayer systems by alternating the oblique angle and the classical configuration geometries. We show that the compact layers develop numerous fissures rooted in the porous structures of the film below, in a phenomenon that amplifies when increasing the number of stacked layers. We demonstrate that these fissures emerge during growth due to the high roughness of the porous layers and the coarsening of a discontinuous interfacial region. To minimize this phenomenon, we have grown thin interlayers between porous and compact films under the impingement of energetic plasma ions, responsible for smoothing out the interfaces and inhibiting the formation of structural fissures. This method has been tested in practical situations for compact TiO/porous SiO multilayer systems, although it can be extrapolated to other materials and conditions.
Authors acknowledge the University of Seville (VPPI-US), the Junta de Andalucía (TEP8067, TEP5283 and P12–2265MO) and the Ministry of Economy and Competitiveness of Spain (MAT2013-42900-P, MAT2013-40852-R, MAT2016-79866-R, MAT2015-69035-REDC) for financial support.