Pk. Larsen et al., FERROELECTRIC PROPERTIES AND FATIGUE OF PBZR0.51TI0.49O3 THIN-FILMS OF VARYING THICKNESS - BLOCKING LAYER MODEL, Journal of applied physics, 76(4), 1994, pp. 2405-2413
Ferroelectric capacitors having Pt bottom and top electrodes and a fer
roelectric film of composition PbZr0.51Ti0.49O3 (PZT) were fabricated
and investigated. The PZT films of thicknesses varying from 0. 12 to 0
.69 mum were prepared by organometallic chemical-vapor deposition. Ann
ealed capacitors were investigated by capacitance, hysteresis, and pul
se switching measurements. It is found that the thickness dependence o
f the reciprocal capacitance, the coercive voltage, and the polarizati
on measured by pulse switching can all be explained by a blocking laye
r model, in which a dielectric layer of thickness d(bl) and relative p
ermittivity epsilon(bl) is situated between the PZT film and an electr
ode. It is shown that (i) the coercive field is independent of thickne
ss having a value of 2.4 V/mum; (ii) the ratio epsilon(bl)/d(bl) is in
the range 20-28 nm-1; (iii) the voltage across the blocking layer is
proportional to the polarization, V(bl)-cP, where c=4.1-0.5 V m2/C; an
d (iv) the polarization depends on the electric field in the PZT layer
, independent of thickness. Pulse switching endurance measurements sho
wed that in the saturation range the fatigue for these ferroelectric c
apacitors is determined by the pulse voltage and is independent of the
thickness.