Interface-induced nonswitchable domains in ferroelectric thin films

Abstract

Engineering domains in ferroelectric thin films is crucial for realizing technological applications including non-volatile data storage and solar energy harvesting. Size and shape of domains strongly depend on the electrical and mechanical boundary conditions. Here we report the origin of nonswitchable polarization under external bias that leads to energetically unfavourable head-to-head domain walls in as-grown epitaxial PbZr 0.2 Ti 0.8 O 3 thin films. By mapping electrostatic potentials and electric fields using off-axis electron holography and electron-beam-induced current with in situ electrical biasing in a transmission electron microscope, we show that electronic band bending across film/substrate interfaces locks local polarization direction and further produces unidirectional biasing fields, inducing nonswitchable domains near the interface. Presence of oxygen vacancies near the film surface, as revealed by electron-energy loss spectroscopy, stabilizes the charged domain walls. The formation of charged domain walls and nonswitchable domains reported in this study can be an origin for imprint and retention loss in ferroelectric thin films.

Coupling of bias-induced crystallographic shear planes with charged domain walls in ferroelectric oxide thin films

“…As shown in dark-field (DF) TEM image ( Fig. 1(e)), 180 o domain walls are only induced in the biased section (P down domain appearing dark while P up bright due to violation of Friedel's law), consistent with our previous report [20]. Interestingly, noticeable defects are also observed in the biased section, but not in the unbiased section ( Fig.…”

“…With increasing concentration of oxygen vacancies, extended defects are experimentally reported in a form of crystallographic shear planes (CSPs) by accumulation of oxygen vacancies in specific planes and then collapsing and shearing the lattice in WO 3 and ReO 3 compounds [17,18]. In perovskites, for in situ electric biasing using commercial TEM holder (Nanofactory Inc.) [20]. Two sections of PZT thin film in a TEM sample were electrically separated by FIB milling, as shown in Fig.…”

Anomalously deep polarization in SrTiO3 (001) interfaced with an epitaxial ultrathin manganite film

“…The off-axis electron holography technique can be used to map the electrostatic potentials and the distribution of the electric field in a film [41]. The distributions of electrostatic potential were determined by the electron-wave phase retrieval, and derived from the function The bottom of Fig.…”

Multiscale differential phase contrast analysis with a unitary detector

“…This is a common task for electronics industry dealing with transistors [1], electronic or magnetic memories [2,3], light-emitting, photovoltaic or multiferroic devices [4][5][6]. A key role for development and production of such devices is the nanoscale characterization of the local magnetic fields in the materials [7][8][9][10][11]. Such characterization is also of paramount importance for biomedical applications like hyperthermia treatment or local drug delivery [12,13].…”