Influence of titanium-substrate roughness on Ca–P–O thin films grown by atomic layer deposition

Amorphous Ca–P–O films were deposited on titanium substrates using atomic layer deposition, while maintaining a uniform Ca/P pulsing ratio of 6/1 with varying number of atomic layer deposition cycles starting from 10 up to 208. Prior to film deposition the titanium substrates were mechanically abraded using SiC abrasive paper of 600, 1200, 2000 grit size and polished with 3μm diamond paste to obtain surface roughness Rrms values of 0.31μm, 0.26μm, 0.16μm, and 0.10μm, respectively. The composition and film thickness of as-deposited amorphous films were studied using Time-Of-Flight Elastic Recoil Detection Analysis. The results showed that uniform films could be deposited on rough metal surfaces with a clear dependence of substrate roughness on the Ca/P atomic ratio of thin films. The in vitro cell-culture studies using MC3T3 mouse osteoblast showed a greater coverage of cells on the surface polished with diamond paste in comparison to rougher surfaces after 24h culture. No statistically significant difference was observed between Ca–P–O coated and un-coated Ti surfaces for the measured roughness value. The deposited 50nm thick films did not dissolve during the cell culture experiment.