Sputtered lead scandium tantalate thin films for dielectric bolometer mode thermal detector arrays

Abstract

This paper describes the deposition of thin film lead scandium tantalate (Pb2ScTaO6) using a novel two target sputtering technique and reports on the effect of post-deposition annealing. The films are deposited on platinum-coated silicon wafers at 300°C and are annealed at a range of temperatures up to 800°C. Vacuum furnace and rapid thermal annealing (RTA) methods are compared. Materials are characterised by X-ray diffraction and show that the as-deposited films form a weak pyrochlore phase which is transformed to perovskite PST by annealing. At anneal temperatures of 750°C and above superlattice ordering is observed. Compositional measurements using Energy Dispersive Spectroscopy show that Lead loss is more severe using furnace annealing than RTA, and a combined RTA/furnace anneal method is proposed. The films demonstrate relaxor dielectric characteristics. Induced pyroelectric measurements have been made to assess the potential of this material for ferroelectric micro-bridge thermal detectors.