Ruthenium oxide electrodes prepared by sol-gel spin-coating

Abstract
Ruthenium oxide thin films were obtained by sol-gel spin-coating. The precursor solution was prepared by dissolving an aqueous solution of rutheniun nitrosyl nitrate Ru(NO)(NO₃)₃ into 2-methoxyethanol. Sols exhibiting appropriate viscosity were spin coated onto (100) Si wafers at 4000 rpm for 30 s following by drying at 300°C for 10 min, and repeated 5 ~ 15 times. The coated wafer was then fired at 400 ~ 800°C for 3 h in air. Crystallized homogeneous RuO₂ films were obtained below 300°C, and further heating at higher temperature improves the crystallinity. The resistivity of the films regularly decreases from 270 to 200 µΩ as the film thickness increases from 150 nm (5 successive coatings) to 450 nm (15 successive coatings). In addition the resistivity remains almost constant up to 700°C. These RuO₂ thin films are to be used as bottom electrodes for the sol-gel deposition of SrBi₂Nb₂O₉ ferroelectric films.