LEAD-ZIRCONATE-TITANATE THIN-FILMS ON GAAS SUBSTRATES

Thin films of the piezoceramic lead zirconate titanate (PZT) of compos ition Pb(Zr0.53Ti0.47)O-3 have been prepared on a platinized GaAs subs trate system using a propanediol based sol-gel technique. A Si3N4 buff er layer was deposited onto the GaAs by plasma-enhanced chemical vapou r deposition so as to minimize Ga and As diffusion during film fabrica tion. Rapid thermal processing (RTP) techniques were used to thermally decompose the sol-gel layer to PZT in a further effort to avoid probl ems of Ga and As diffusion. Adhesion between the electrode and substra te was found to improve when an intermediate Ti layer deposited betwee n the Pt and Si3N4 was oxidized prior to depositing the Pt layer. A cr ystalline PZT film was produced on the Pt/TiO2/Si3N4/GaAs by firing th e sol-gel coating at 350 degrees C for 1 min and then at 650 degrees C for 10 s using RTP. A single deposition of precursor sol resulted in a film 0.5 mu m thick. Measured average values of remanant polarizatio n and coercive field were 14 mu C cm(-2) and 47 kV cm(-1), respectivel y. The polarization value is rather low, as conventionally fired films on silicon have remanent polarization values of 20-30 mu C cm(-2); th e lower values may be due to incomplete crystallization during RTP, bu t a degradation of properties due to Ga-As diffusion, despite the prec autions, cannot be ruled out at this stage.