Synthesis and characterization of aperiodic multifunctional AlN/Al2O3 nanomultilayers

Optical-mechanical multifunctionality in ceramic nanomultilayered coatings is an area of research relatively unexplored. Particularly, layer aperiodicity has been shown to improve transmittance, where the effect on mechanical deformation remains unknown. Here, AlN/Al₂O₃ nanomultilayers are synthesized via sputtering with four unique, optically optimized aperiodic layer structures with a minimum ultraviolet-visible-near-infrared transmittance of 90% and with an Al₂O₃ volume fraction ranging from 30% to 73%. Deformation was explored at different length scales, revealing the effect of local volume fraction and individual layer thicknesses within the aperiodic structure. It was determined that the deformation behavior is correlated to the local AlN or Al₂O₃ volume fraction within a given layer stack, where individual layer thickness and adjacent layer interactions were shown to affect crack propagation.