Effects of substrate properties, film thickness and evaporation rate on the surface roughness of ultra thin titanium films

Ultra thin (less than 50nm) titanium films with various thicknesses are systematically deposited on different substrates by electron-beam evaporation at various deposition rates in order to correlate flat titanium film surface roughness with deposition process parameters. In this paper, the influences of the substrate surface properties, film thickness and evaporation rate on surface roughness of flat ultra thin titanium films are clarified. In this study, distinct and abrupt steps on the film surface were fabricated by masks pasted on the substrate surfaces during the deposition process. The step can be scanned with stylus profilometer to reveal the height of the step (the thickness of the thin film). Ultra thin films with height 20-50 nm were routinely measured in this way. It is important to notice that ultra thin titanium films with different surface roughness but having the same film thickness can be obtained in a controllable way. Therefore, the control of substrate surface roughness, film thickness and evaporation process is essential to prepare ultra thin titanium films with desired surface properties in reproducible way for further biological and nanostructure investigations of these materials.