Substrate heterostructure effects on interface composition, microstructure development and functional properties of PZT thin films

摘要

Platinum- and (La_(0.8),Sr_(o.2))MnO_3 (LSMO)-terminated silicon substrates were used for the liquid-phase deposition of Pb(Zr_(0.52),Ti_(0.48))O_3 (PZT) thin films. Different layer thicknesses ranging from 100 to 600 nm were processed by sequential coating. Characterization of the films involved X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy (XPS) combined with depth profiling to probe the interface composition. The films deposited on Pt exhibit an intermetallic layer, Pt_xPb, after annealing at 500 deg C in air. This film has been used to establish the XPS signature of the intermetallic phase which consists of a negative shift of the peak position of Pt(4f) due the electron transfer from Pb to Pt. In all cases pure phase perovskite thin films were obtained after short annealing at 700 deg C. XPS depth profiling shows unambiguously the existence of an intermetallic layer, Pt_xPb, of approximately 10 nm at the interface between Pt and PZT, while an interdiffusion layer of approx 30 nm was observed between LSMO and PZT. The impacts of interfacial layers on microstructure development and functional properties translate in the formation of specific textures, i.e. a pronounced (111)-texture on Pt due to lattice matching between (111)-PZT and (111)-Pt_xPb, and a random film orientation on LSMO, and a substantial thickness dependence of the dielectric and ferroelectric properties, though specific behaviors were observed for the two different substrate heterostructures.