Effects of Titanium Buffer Layer on Lead-Zirconate-Titanate Crystallization Processes in Sol-Gel Deposition Technique

Abstract

Effects of the Ti buffer layer on crystallization processes of lead-zirconate-titanate (PZT) films by the sol-gel deposition technique were investigated. The Ti buffer layer was deposited on a Pt/TiN/SiO₂/Si substrate by electron beam evaporation at the back-pressure of 1×10^-11 Torr. Homogeneous crystalline PZT film of perovskite structure with fine grains were successfully obtained on the substrate with a Ti buffer layer. In contrast, a rosette-structure film which consists of large grains surrounded by a second phase was formed on a pure Pt surface. Ti existing at the interface between Pt and PZT acts as nuclei, and affects the growth of fine grains. Furthermore, leakage current density was drastically reduced from 5×10^-5 A/cm² to 6×10^-9 A/cm² at 4 V for 200-nm-thick film formed on a substrate with a buffer layer. Crystalline orientations and microstructures of PZT films were strongly dependent on the equivalent thickness of the buffer layer and there was an optimum thickness. When the equivalent thickness of the buffer layer was 2 nm, PZT showed -preferred orientation and a homogeneous film structure with fine grains on the -oriented Pt/SiO₂/Si substrate.