Toward energy-efficient physical vapor deposition: Routes for replacing substrate heating during magnetron sputter deposition by employing metal ion irradiation

• Published in: Surface & coatings technology 2021-06, Vol.415, p.127120, Article 127120
• Main Authors: Li, X., Bakhit, B., Jõesaar, M.P. Johansson, Hultman, L., Petrov, I., Greczynski, G.
• Format: Article
• Language: English
• Subjects: Aluminum; Chromium; Control stability; Densification; Energy consumption; Film growth; Heating; HiPIMS; Ion irradiation; Low temperature; Low-temperature growth; Magnetron sputtering; Mechanical properties; Metal ions; Molybdenum; Nanostructure; Oxygen content; Phase stability; Physical vapor deposition; Substrates; Sustainable development; Thin films; TiAlN; Titanium; Transition metals; Tungsten
• ISSN: 0257-8972; 1879-3347; 1879-3347
• DOI: 10.1016/j.surfcoat.2021.127120

In view of the increasing demand for achieving sustainable development, the quest for lowering energy consumption during thin film growth by magnetron sputtering becomes of particular importance. In addition, there is a demand for low-temperature growth of dense, hard coatings for protecting temperature-sensitive substrates. Here, we explore a method, in which thermally-driven adatom mobility, necessary to obtain high-quality fully-dense films, is replaced with that supplied by effective low-energy recoil creation resulting from high-mass metal ion irradiation of the growing film surface. This approach allows the growth of dense and hard films with no external heating at substrate temperatures Ts not exceeding 130 °C in a hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) setup involving a high mass (m > 180 amu) HiPIMS target and metal-ion-synchronized bias pulses. We specifically investigate the effect of the metal ion mass on the extent of densification, phase content, nanostructure, and mechanical properties of metastable cubic Ti0.50Al0.50N based thin films, which present outstanding challenges for phase stability control. Ti0.50Al0.50N based thin films are irradiated by group VIB transition metal (TM) target ions generated by Me-HiPIMS discharge, in which Me = Cr (mCr = 52.0 amu), Mo (mMo = 96.0 amu), and W (mW = 183.8 amu). Three series of (Ti1-yAly)1-xMexN films are grown with x = Me/(Me+Al+Ti) varied intentionally by adjusting the DCMS powers, while y = Al/(Al+Ti) also varies as a result of Me+ ion irradiation. Results reveal a strong dependence of film properties on the mass of the HiPIMS-generated metal ions. All layers deposited with Cr+ irradiation exhibit porous nanostructure, high oxygen content, and poor mechanical properties. In contrast, (Ti1-yAly)1-xWxN films are fully-dense even with the lowest W concentration, x = 0.09, show no evidence of hexagonal AlN precipitation, and exhibit state-of the-art mechanical properties typical of Ti0.50Al0.50N grown at 500 °C. The process energy consumption is lowered by 64% with no negative impact on the coating quality. TRIM simulations provide an insight into the densification mechanisms. •(Ti1-yAly)1-xMexN (Me = Cr, Mo, W) thin films are grown by Me-HiPIMS/TiAl-DCMS.•The effect of the metal ion mass on the Ti0.50Al0.50N densification is studied.•No external heating is applied during coating and substrate temperature is lower than 130 °C.•Dense films are achieved with W ions resul