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

Highlights: • Bi₂Ru₂O₇ thin films were deposited by chemical vapor deposition process. • The process window for epitaxial pyrochlore Bi₂Ru₂O₇ film growth was confirmed. • The resistivity of the Bi₂Ru₂O₇ films was close to that of a single crystal Bi₂Ru₂O₇. -- 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.