The state of coating-substrate interfacial region formed during TiO2 coating deposition by Gas Injection Magnetron Sputtering technique

This manuscript presents the nature of interaction of energetic plasmoids, generated in the Gas Injection Magnetron Sputtering (GIMS) technique, with the surface of substrate or the coating-substrate system. We expected that the plasma generated by a dynamic injection of gas (GIMS) is better ionized than the plasma generated in stationary pressure in its standard range for magnetron sputtering. The GIMS technique operates under conditions that may favor the plasma species to retain their kinetic energy, limiting the probability of intermolecular collisions events. In this experiment, the frequency of injecting small amounts of gas was used as a parameter to control the pressure amplitudes, thus achieving the conditions of plasma generation from stationary, through quasi-stationary, to pulsed oscillations of pressure. The optical emission spectroscopy (OES) was used to evaluate the state of deposition environment in GIMS. Investigation showed that the plasma spectrum consists of higher population of ions in the conditions of high amplitude of pressure oscillations. The phase content of a titanium dioxide coating, deposited under various conditions of plasma generation, also depends on the energetic state of plasma. Raman spectroscopy proved that the stationary condition favors the anatase phase as the nucleation phase, while with the increase in the non-equilibrium of plasma, the metastable rutile phase is more expected. The effects of strong impingement of energetic species were observed, causing crystallization of the amorphous phase of coatings, with sputtering of the substrate surface and the formation of a specific type of coating-substrate interfacial region.