Epitaxial growth and structural properties of conductive RuO₂ thin films

Metal-organic chemical vapor deposition (MOCVD) has been used to deposit conductive oxide RuO₂ thin films at different temperatures on (100) MgO and (100) LaAlO₃ substrates. The microstructural properties of the RuO₂ films have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). Different growth and microstructural properties were observed for the films deposited on the two substrates. For example, the films on MgO are epitaxial at deposition temperatures as low as 350°C, and the films on LaAlO₃ are epitaxial only at deposition temperatures of 600°C and above. The epitaxial films on MgO consist of two variants with an orientation relationship given by (110) RuO₂//(100) MgO and [001] RuO₂//[011]MgO. The epitaxial films on LaAlO₃, on the other hand, contain four variants with an orientation relationship given by (200)RuO₂//(100)LaAlO₃ and [011] RuO₂//[011] LaAlO₃. The difference in growth and microstructural properties were explained based on geometrical considerations for the film and substrates. The RuO₂/substrate interfaces and the RuO₂ domain boundaries were also investigated by TEM and HREM.