Plasma Sputtering of a Nanostructured Hafnium-Oxide Coating by Means of a Prandtl–Meyer Flow

The geometric characteristics of the supersonic nozzle of a plasmatron intended for vacuum plasma sputtering, which creates a Prandtl–Meyer expansion fan, are estimated. The nozzle facilitates nanoparticle condensation from the vapor phase of the sputtered material due its cooling in the vicinity of the nozzle cross section rotated by 6° and 27°. During the process of sputtering, a coating containing mainly large-scale particles and their fragments and a film consisting of nanoparticles are formed if the central part of the nozzle and its peripheral regions pass over the sample, respectively. Investigation into the surface structure of a HfO2–9% Y2O3 coating 30 μm thick indicates the existence of deformed particles and nanostructured regions in the form of thin film fragments.