Control of film orientation: a parametric study of laser ablated FTO films on a-, c- and r-cut sapphire substrates by X-ray diffraction

Abstract

Parametric work has been done to prepare FeTiO3 (FTO) thin films on A-, C-, and R-cut sapphire substrates. We have found that the preparation of highly oriented FTO films on different cut substrates is strongly dependent on substrate temperature, laser energy density and gas pressure. The orientations of FTO thin film can be controlled both by varying substrate cut direction and laser energy density. By varying the substrate cut directions, epitaxial thin films with high quality have been successfully grown on both A- and C-cut sapphire substrates with different substrate temperatures. The orientation control can also be realized by changing laser energy density, and we have grown both (112̄0) and (0006) oriented films on A-cut substrates with different laser energy densities. Higher laser energy density developed the tendency of film growth along the (0006) direction on A-cut substrates. At the same time, higher laser energy density enhances (0006) film growth on C-cut sapphire too. We have also found that epitaxial films can be grown on A-cut sapphire substrates in a quite large temperature range from 450 to 600°C. However, we have not got epitaxial film on R-cut sapphire substrate in a quite wide temperature range from 300 to 600°C. Probably it can be grown at a higher temperature which now is not accessible to our PLD system.