N. Balke | Searcharxiv

arXiv2013

Unit cell orientation of tetragonal-like BiFeO$_3$ thin films grown on highly miscut LaAlO$_3$ substrates

Synchrotron and lab-scale x-ray diffraction shows that tetragonal-like T'-BiFeO3 films on miscut LaAlO3 substrates (miscut < 5 deg) exhibit (00l)-planes tilted away from those of the substrate as predicted by the "Nagai model" (except for miscut <0.2 deg). Tilts as large as 1 deg are achieved even in 100 nm thick films, strikingly larger than those observed in other perovskites. We attribute this to the large c/a ratio and the high crystalline coherency of the T'-BiFeO3/LaAlO3 interface. This coherency is possible through an observed "diagonal-on-diagonal" alignment. Interestingly, the substrate miscut does not influence the relative population of monoclinic domains.

cond-mat.mtrl-sci↗

arXiv2010

Local probing of ionic diffusion by electrochemical strain microscopy: spatial resolution and signal formation mechanisms

Electrochemical insertion-deintercalation reactions are typically associated with significant change of molar volume of the host compound. This strong coupling between ionic currents and strains underpins image formation mechanisms in electrochemical strain microscopy (ESM), and allows exploring the tip-induced electrochemical processes locally. Here we analyze the signal formation mechanism in ESM, and develop the analytical description of operation in frequency and time domains. The ESM spectroscopic modes are compared to classical electrochemical methods including potentiostatic and galvanostatic intermittent titration (PITT and GITT), and electrochemical impedance spectroscopy (EIS). This analysis illustrates the feasibility of spatially resolved studies of Li-ion dynamics on the sub-10 nanometer level using electromechanical detection.

cond-mat.mtrl-sci↗