Direct observation of single domains in poled (111) PZT (PbZr0.25Ti0.75O3)films

Films of(Ill) oriented poled ferroelectric lead zirconate titanate (PZT) cr ystallites on (100)Si/SiO2/(111) Pt were investigated by scanning tunneling microscopy (STM), atomic force microscopy (AFM) and small angle X-ray scat tering (SAXS). SAXS investigations allowed to estimate a mean value of domain thickness of 17.5 nm. Exertion of stress (5.1 x 10(4) N m-2) to the film resulted in an increase of domain width of similar to 1%. After metallization of the PZT surface with a Cr-Ni film of 5.2 nm or a Ti film of 5.0 nm thickness, domains were visible by STM measurements as paral lel stripes on the surface with a width of 15-20 nm. A downward Vertical co rrugation of 1.0-1.5 nm typically occurred at the intersection site of doma in walls with the surface. Its presence is ascribed to shear strain origina ting from coherency defects in the interface. High resolution AFM with electron beam deposited supertips on unmetallized samples revealed areas of typically several micrometers in diameter showing crystallites with perfectly aligned domains of 10-15 nm width. The domains formed parallel slabs of twinned-crystallites with their polarization c-ax is changing alternately from [001] to [010] direction. For a fully poled (I ll) PZT film, the c-axis of each (90 degrees) domain is inclined towards th e surface by 35 degrees and tilted against the surface normal by +45 or -45 degrees, respectively. These results generally confirm the Speck-Streiffer -Pompe-Romanov domain model which predicts for a (111) PZT film of 500 nm t hickness a polyvariant with alternating (90 degrees) domains of 16.4 nm wid th. (C) 1999 Elsevier Science B.V. All rights reserved.