Systematic Application of Extremely Large Strain to Rutile-Type RuO<sub>2</sub>(100) Epitaxial Thin Films on Substrates with Large Lattice Mismatches
Zainab Fatima, Daichi Oka, Tomoteru Fukumura
Abstract
We demonstrate the systematic control of lattice strain in rutile-type RuO2(100) epitaxial thin films grown on yttria-stabilized zirconia (YSZ)(111) and α-Al2O3(0001) single-crystal substrates at various growth temperatures. The lattice strain monotonically increased by decreasing the growth temperature up to an extremely large value of 6.5%. A morphological transition in the film surface from two-dimensional (2D) to three-dimensional (3D) by decreasing the growth temperature indicated that growth-mode-induced strain contributed to the lattice strain. The thickness dependence of the strain also suggested a significant contribution of the lattice mismatch at the film/substrate interface and domain boundaries. The electrical resistivity and its temperature derivative were almost unchanged under the lattice strain up to 5%, which guarantees the reliable applications of RuO2 for catalysts and electrodes.