Effect of Sputtering Power on in vitro Bioactivity of Zirconia Thin Films Obtained by DC Unbalanced Magnetron Sputtering

This work aims to deposit ZrO2 thin films on type 316L-stainless steel substrates by DC unbalanced magnetron sputtering under various sputtering powers in the range of 120-300 W. The target-to-substrate distance was adjusted to 100 mm and the deposition time was 120 min. The XRD results demonstrate that the sputtered ZrO2 is a monoclinic phase. The AFM analysis reveals that the grain size, root mean square surface roughness and thickness of ZrO2 films increase with increasing sputtering power. The deposited substrates were soaked in a simulated body fluid (SBF) with ion concentrations near human blood plasma to examine the biocompatibility properties on the surface though in vitro study. The XRD, FT-IR, and SEM results show correspondingly that all ZrO2 surfaces were covered with apatite after 7 d of immersion in SBF. The conditions of preparing films at low sputtering power with smaller grain size and larger number of grain boundaries per unit length are considered to be the favorable conditions for apatite growth on ZrO2 films owing to the large specific area.