Structural defects and local chemistry across ferroelectric–electrode interfaces in epitaxial heterostructures

Abstract

We present a detailed investigation of the chemistry at the growth interface between the bottom electrode and ferroelectric film in (001)-oriented epitaxial ferroelectric thin-film heterostructures. Three different ferroelectric systems, namely PbZr 0.2 Ti 0.8 O 3 , PbZr 0.52 Ti 0.48 O 3 , and BaTiO 3 deposited on SrRuO 3 /SrTiO 3 , were investigated to compare and contrast the role of lattice mismatch versus the volatility of the deposited cation species. A combination of transmission electron microscopy-based imaging and spectroscopy reveals distinct correlations among the ferroelectric thin-film composition, the deposition process, and chemical gradients observed across the ferroelectric-electrode interface. Sr diffusion from the electrode into the ferroelectric film was found to be dominant in PbZr 0.2 Ti 0.8 O 3 /SrRuO 3 /SrTiO 3 thin films. Conversely, Pb diffusion was found to be prevalent in PbZr 0.52 Ti 0.48 O 3 /SrRuO 3 /SrTiO 3 thin films. The BaTiO 3 / SrRuO 3 /SrTiO 3 heterostructure was found to have atomically sharp interfaces with no signature of any interdiffusion. We show that controlling the volatility of the cation species is as crucial as lattice mismatch in the fabrication of defect-free ferroelectric thin-film devices.

Direct Evidence for Cation Non‐Stoichiometry and Cottrell Atmospheres Around Dislocation Cores in Functional Oxide Interfaces

“…The EDX maps presented here provide evidence for Pb segregation around the dislocation core. Finally, we show that Ru (Figure 1g) exhibits no diffusion (also previously confirmed [19] ) and hence, it was used to locate the interface. The EDX mapping above was complemented by atomic-scale EELS analysis to further explore the effect of the cation variations on the electronic configurations of the oxygen sublattice at and around the dislocation core.…”

Chemistry of Ruddlesden–Popper planar faults at a ferroelectric–ferromagnet perovskite interface

“…7(h)] shows little diffusion into the PZT layer. A similar process to the above was reported for PZT/SrRuO 3 heterostructures, 25 where Asite diffusion was found to be more dominant. The Mn-Ka and Zr-La maps [Figs.…”

Are ferroelectric multilayers capacitors in series?

“…In fact, all microstructural elements (such as elastic and electrical domains, grain and phase boundaries, dislocations, etc. ), and point defects such as vacancies and internal stresses (thermal and/or epitaxial) play an important role in the functional response of a FE material [59][60][61][62]. Local fields (electrical and mechanical) around such features will certainly affect the global electrostatic and electromechanical fields resulting from the polarization mismatch.…”