Abstract
Hybrid high power impulse/direct current magnetron sputtering (HiPIMS/DCMS) film growth technique with metal-ion-synchronized substrate bias allows for significant energy savings as compared to conventional PVD methods. For carefully selected type of metal ion irradiation, taking into account ion mass, ionization potential, and reactivity towards working gas, fully dense and hard films can be obtained with no intentional substrate heating. The thermally-driven adatom mobility, which is an essential densification mechanism in conventional film growth that takes place at elevated temperatures, is replaced with that supplied by effective low-energy recoil creation. In this contribution we explore effects of the high-mass W+ irradiation, which has proven to be the most efficient in densifying Ti0.50Al0.50N layers, serving here as a model system, grown with no substrate heating. We study the effects of two essential parameters: W+ energy EW+ and W concentration x, on film porosity, phase content, nanostructure, and mechanical properties. EW+ varies from ~90 to ~630 eV (controlled by substrate bias voltage amplitude Vs) and x from 0.02 to 0.12 (controlled by the HiPIMS pulse length), while the HiPIMS peak target current is kept constant. Results reveal that a strong coupling exists between the W+ incident energy and the minimum W concentration required to grow dense layers.
Highlights
Physical vapor deposition (PVD) techniques, despite being consid ered more environmentally friendly than other coating processes such as electroplating or chemical vapor deposition, traditionally require high amounts of energy primarily consumed for substrate heating to ensure sufficient adatom mobility
In a previous paper we investigated the effect of metal-ion mass by irradiating metastable cubic Ti0.50Al0.50N based thin films, by group VIB transition metal (TM) target ions generated by Me-HiPIMS discharge, in which Me = Cr, Mo, and W [14]
We study the effects of two essential parameters: W+ energy EW+ and W concentration on the metal lattice x = W/(W+Ti+Al) during growth of (Ti1-yAly)1-xWxN films by W-HiPIMS/TiAl-DCMS approach with no external heating
Summary
Physical vapor deposition (PVD) techniques, despite being consid ered more environmentally friendly than other coating processes such as electroplating or chemical vapor deposition, traditionally require high amounts of energy primarily consumed for substrate heating to ensure sufficient adatom mobility. High deposition temperatures (typically in the 400–600 ◦C range) prevent depositions on heat-sensitive substrates, effectively excluding modern engineering and construction materials such as lightweight Al- and Mg-based alloys. Apart from providing thermally-induced adatom mobility during film growth the extensive heating ensures cleaner deposition con ditions by effectively reducing the water vapor content in the residual atmosphere. The latter process requires, much lower temper atures as effective water desorption from the vacuum chamber walls and components are triggered already at 100 ◦C. The primary chal lenge towards energy-efficient PVD is to find alternatives for replacing thermally-driven diffusion during film growth to obtain high-quality fully-dense layers, while controlling residual gas contamination
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