High-mass metal ion irradiation enables growth of high-entropy sublattice nitride thin films from elemental targets

Abstract

Synthesis of high-entropy sublattice nitride (HESN) coatings by magnetron sputtering is typically done using custom-made alloyed targets with specific elemental compositions. This approach is expensive, requires long delivery times, and offers very limited flexibility to adjust the film composition. Here, we demonstrate a new method to grow HESN films, which relies on elemental targets arranged in the multicathode configuration with substrates rotating during deposition. TiVNbMoWN films are grown at a temperature of ∼520 °С using Ti, V, Nb, and Mo targets operating in the direct current magnetron sputtering mode, while the W target, operated by high power impulse magnetron sputtering (HiPIMS), provides a source of heavy ions. The energy of the metal ions EW+ is controlled in the range from 80 to 620 eV by varying the amplitude of the substrate bias pulses Vs, synchronized with the metal-ion-rich phase of HiPIMS pulses. We demonstrate that W+ irradiation provides dynamic recoil mixing of the film-forming components in the near-surface atomic layers. For EW+ ≥ 320 eV the multilayer formation phenomena, inherent for this deposition geometry, are suppressed and, hence, compositionally uniform HESN films are obtained, as confirmed by the microstructural and elemental analysis.