Growth of epitaxial bismuth ruthenate pyrochlore films on yttria-stabilized zirconia (YSZ) and YSZ-buffered Si substrates by metal–organic chemical vapor deposition

Abstract

Bismuth ruthenate (Bi2Ru2O7) thin films were deposited on (111) yttria-stabilized zirconia (YSZ) single crystals and (111)YSZ//(111)Si substrates by chemical vapor deposition using Bi(CH3)2[2-(CH3)2NCH2C6H4] and Ru(C7H11)(C7H9) as source materials and oxygen as a reactant gas. The film composition and X-ray diffraction ω-2θ scan profiles for thin films deposited using various source flow rate ratios revealed the existence of a process window to obtain stoichiometric Bi2Ru2O7. Within the process window, the kind of substrates did not strongly affect the deposition rates of Bi and Ru or the Bi/Ru ratio of the deposited films. It was also confirmed that the Bi2Ru2O7 thin films grew epitaxially on both substrates within the process window. In particular, epitaxial Bi2Ru2O7 thin films grew on the Si substrate with a YSZ buffer layer. Scanning electron microscopy revealed the formation of continuous dense Bi2Ru2O7 films without any cracks or voids, and a relatively smooth interface between Bi2Ru2O7 and the YSZ buffer layer on Si. The resistivity of the Bi2Ru2O7 films was almost constant (~550 and ~950 μΩcm for the films deposited on (111)YSZ single-crystal substrates and (111)YSZ//(111)Si substrates, respectively), even when the ratio of Bi and Ru source gas flow rates was changed in the process window. In addition, the resistivity of Bi2Ru2O7 films prepared on both kinds of substrates was almost independent of temperature from 10 to 300 K.