Control of crystalline structure and ferroelectric properties of Pb(ZrxTi/sub 1-X/)O3 films by pulsed laser deposition
We have investigated Pb(Zr/sub X/Ti/sub 1-X/)O/sub 3/ (PZT) films on Pt/SiO/sub 2//Si substrates formed by pulsed laser deposition (PLD) and subsequent rapid thermal annealing (RTA) under various growth conditions. X-ray diffraction analysis revealed that preferentially [100]-oriented perovskite PZT films with trigonal structure were formed after RTA from as-deposited films which had consisted of small grains with pyroclore structure. The degree of [100]-orientation of the PZT film increased with the oxygen partial pressure during PLD. The capacitors made from these films showed higher remnant polarization than those from randomly oriented films.
Preparation of Pb(Zr,Ti)O3 Thin Films on Ir and IrO2 Electrodes
Pb(Zrx Ti1-x )O3 (PZT) thin films were prepared on Ir and IrO2 electrodes. Ir has very similar properties to Pt, and IrO2 is a conductive oxide. Perovskite single-phase PZT thin films were obtained on their electrodes. PZT thin films were grown by the conventional sol-gel method with rapid thermal annealing (RTA) at 700° C. When Pt thin films were deposited directly on poly-Si, PtSi layers were formed, and PZT thin films on the Pt had very poor crystallinity. When an IrO2 layer was formed between PZT and poly-Si, a high-quality PZT thin film was obtained. Moreover, when electrodes including the IrO2 layer were used, fatigue properties of PZT thin films were drastically improved.
Phase Transitions in Solid Solutions of PbZrO3 and PbTiO3 (I) Small Concentrations of PbTiO3
The dielectric, calorimetric and dilatometric measurements have been made on the solid solutions Pb(Zr-Ti)O 3 which contain small amounts of PbTiO 3 less than 10%. Besides the ordinary Curie point near 220°C, the existence of another transition, for example 140°C in Pb(Zr95-Ti5)O 3 , was confirmed. It seems reasonable to interpret these two transitions as phase changes from paraelectric state to ferroelectric one and further to antiferroelectric one. Whereas the upper transition temperature is nearly constant for these concentrations, the lower transition temperature increases with decreasing Ti concentration and both temperatures seem to coincide at pure PbZrO 3 . These results suggest that PbZrO 3 may be antiferroelectric below its Curie point 220°C.