Room-temperature fabrication of hard AlN/TiN superlattice coatings by pulsed laser deposition

Abstract

Factors affecting the stability of the deposition rate of TiN and AlN during pulsed laser deposition (PLD) were studied using a quartz crystal microbalance technique. Monitoring of optical emission of plasma generated during laser ablation proved effective for stabilizing the deposition rates during superlattice fabrication. As a result, high-quality AlN/TiN superlattices with a pronounced hardness enhancement effect have been fabricated for the first time by the PLD technique at room temperature. The coatings were studied by a nanoindentation technique based on a scanning probe microscope, low-angle x-ray diffraction, and atomic force microscopy. Drastic changes in the nanohardness and surface morphology were observed in AlN/TiN structures when the bilayer period was reduced below 3 nm. These changes were assigned to a hexagonal-to-cubic phase transformation in AlN.