Pulsed laser deposition of high-epsilon dielectrics: PMN and PMN-PT

Abstract

In this study we report on the KrF excimer laser deposition of crystalline films of lead magnesium niobium oxide (PMN) and solid solutions of PMN and lead titanate (PT) in a 65:35 ratio. These materials have potential microelectronic applications as thin film capacitors due to their high dielectric constants (εPMN(bulk)≳10,000). Films were typically deposited in an oxygen background at elevated substrate temperatures (Ts = 525 °C) on substrates of Pt(111)/SiO2/Si or Pt(111)/glass. The deposited films were characterized by Rutherford Backscattering Spectroscopy (RBS), x-ray diffraction, and capacitance/loss measurements. Films prepared from a nearly stoichiometric commercial PMN target were low in Mg and Pb and yielded only the low-ε pyrochlore phase (measured εfilm≈100), even after ex-situ annealing at temperatures up to 650 °C. Films deposited from Pb, Mg-rich targets prepared by a sol-gel process (tailored to produce the desired film stoichiometry) contained mixtures of perovskite and pyrochlore, with typical ε values of order 600-1200.