Formation of lead lanthanum zirconate titanate films by heat treatments

摘要

Lead lanthanum zirconate titanate (PLZT) also called lanthanum doped PZT films were deposited by RF magnetron sputtering. PLZT in the perovskite phase is required to obtain a film with a large electro-optic effect. It can also be used as a ferroelectric and piezoelectric material. However films that have not been heat treated either during or after deposition are typically in the pyrochlore phase. Perovskite PLZT films obtained by heating the substrate during sputtering showed little evidence of cracks in the films sputtered without heating the substrate were not in the Perovskite phase and post deposition annealing was required to do so. Both furnace and rapid thermal annealing were investigated but in both cases cracks formed in the films to various degrees. Such films are unsuitable for optical device fabrication. To determine the orientation of PLZT films X-ray diffraction (XRD) spectras were obtained and compared. Samples were prepared on silicon substrates which had a thin film of 20 nm Ti/100 nm Pt deposited by electron beam evaporation. Sputtering was done in an argon atmosphere using a PLZT (9/65/35) target. Thicknesses of 1 mum were obtained. Some samples were heated during sputtering up to a temperature of 650 degC. Annealing temperatures were varied from 500 to 750 degC. The best results (determined by XRD) were obtained for RTA at 750 degC for 10 minutes in air. XRD spectra of before and after annealing show a significant increase in the Perovskite peaks. The patterning of these films to form optical waveguides by ion beam etching is also presented. The samples were patterned with photoresist masks and ion beam etched using argon at a gun voltage of 500 V