Highly (111) oriented lead zirconate titanate thin films deposited using a non-polymeric route

Abstract

This paper presents a simple non-polymeric solution route and its process conditions for depositing reproducible very highly (111) oriented lead zirconate titanate Pb(Zr 0.53, Ti 0.47)O 3 (abbreviated PZT) thin films, with an excellent combination of electrical properties, on Pt(111)/Ti/SiO 2/Si wafers. Unlike sol–gel derived routes, non-polymeric methods do not rely on polymerisation in solution of metal precursors, so that the viscosity of the starting sol remains constant, which is important for good reproducibility in the commercialisation of ‘micro electro mechanical systems’ (MEMS). The route presented uses Pb 2-ethylhexanoate, Ti (diisopropoxide) bis (2,4-pentanedionate), and Zr n-butoxide, mixed in the solvent xylene. Sol preparation is performed in an open atmosphere, without the need for refluxing. Crystallisation was carried out both by conventional furnace annealing and rapid thermal annealing (RTA). With furnace annealing, precursor solutions with 30% excess Pb produced films with satisfactory ferroelectric properties; whilst by reaching the onset of perovskite crystallisation rapidly with RTA, starting solutions with only 10% Pb excess produced perovskite PZT films with excellent electrical properties (relative permittivity ε r∼1700, remnant polarisation P r∼20 μC/cm 2 and coercive field E c∼55 kV/cm), with a high degree of (111) orientation. Both (111)/(100) and (111)/(110) X-ray diffraction peak intensity ratios were above 100. The films were 1 μm thick.