In-situ growth of Pb(Zr_0.5Ti_0.5)O₃/RuO₂ heterostructures on Si(001) using low-temperature metal-organic chemical vapor deposition

Abstract

Pb(Zr_0.5Ti_0.5)O₃/RuO₂ thin film heterostructures were successfully grown on SiO₂/Si(001) substrates using metal-organic chemical vapor deposition with a maximum processing temperature of 525°C. To form the heterostructures, (110)-textured RuO₂ electrode layers were first deposited on SiO₂/Si(001) substrates at temperatures as low as 350°C at a typical grow rate of μΩ40Å/min. The resistivity of the RuO₂ films was 30–40 μΩ-cm. Plan-view transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed that typical RuO₂ films had a grain size of 800–1000Å with surface roughness of 3–25 nm, respectively. Perovskite phase Pb(Zr_0.5Ti_0.5)O₃ (PZT) was then deposited at 525°C. The as-deposited films exhibited a dense, randomly-oriented crystal structure with a grain size of ∼800–1000Å. Using capacitors defined with Ag top electrodes, the film showed a remanent polarization of 21.5 μC/cm² and a coercive field of 39.0 kV/cm. The capacitors showed little fatigue up to ∼10¹⁰ cycles. The as-deposited films exhibited high resistivity (10¹²-10¹³ Ω-cm at 100 kV/cm). The current versus voltage characteristics show that the films have typical dielectric breakdown strengths of ∼60 V/μm with a sub-breakdown leakage current density of 5×10⁻⁵ A/cm².