Growth of TiO 2 thin films on Si(1 0 0) and Si(1 1 1) substrates using single molecular precursor by high-vacuum MOCVD and comparison of growth behavior and structural properties

Abstract

We have deposited titanium dioxide (TiO 2) thin films on Si(1 0 0) and Si(1 1 1) substrates in the temperature range of 500–750°C and in the pressure range of 3.0×10 −7–5.0×10 −5 Torr using a single molecular precursor such as titanium (IV) iso-propoxide (Ti[OCH(CH 3) 2] 4, 97%) by high-vacuum metal-organic chemical vapor deposition method. Highly oriented, stoichiometric TiO 2 thin films with rutile phase were successfully deposited on both Si(1 0 0) and Si(1 1 1) substrates between 650°C and 750°C under a working pressure of 1.0×10 −5 Torr. X-ray diffraction results clearly showed different growth behaviors between Si(1 0 0) and Si(1 1 1) substrates. The main film growth directions are [1 1 0] on Si(1 0 0) and [2 0 0] on Si(1 1 1), respectively. Scanning electron microscope and transmission electron microscope images showed a quite smooth surface with no cracks and sharp interface between film layers, suggesting good adhesion and uniformity in depth. In the case of TiO 2 films, grown under low temperature below 600°C and high pressure above 3.0×10 −5 Torr, transmission electron diffraction pattern showed a mixed structure with spot and ring patterns, resulting in polycrystalline film formation. By increasing the growth temperature to 650°C and decreasing the pressure to 3.0×10 −7 Torr, however, strong spot images with weak ring pattern were observed, indicating that the film crystallinity as well as growth direction was strongly affected by deposition temperature and pressure.