Electromechanics of Ferroelectric‐Like Behavior of LaAlO₃ Thin Films

Abstract

Electromechanical coupling in complex oxide heterostructures opens new possibilities for the development of a broad range of novel electronic devices with enhanced functionality. In this article, the switchable hysteretic electro mechanical behavior of crystalline epitaxial LaAlO 3 (LAO) thin fi lms associated with polarization induced by electrical and mechanical stimuli is investigated. The fi eld-time-dependent testing of the induced polarization states along with transport measurements and theoretical modeling suggests that the ferroelectric-like response of the LAO thin fi lms is mediated by the fi eld-induced ion migration in the bulk of the fi lm. Comparative analysis of the dynamics of polarization reversal under the electrical fi eld and mechanical stress applied via a tip of a scanning probe microscope demonstrates that both electrical and mechanical stimulus can be used to effectively control polarization at least at the submillisecond timescale. However, the mechanical writing is more localized than the electrical one. A combined electrical/ mechanical approach for tuning the physical properties of oxide heterostructures may potentially facilitate novel memory and logic devices, in which the data bits are written mechanically and read electrically.

Direct observation of polar tweed in LaAlO3

“…We finally mention that polarity in thin films of LaAlO 3 have been reported in the pioneering paper by Sharma et al 57. These authors describe the switchable hysteretic electro-mechanical behaviour of crystalline epitaxial LaAlO 3 thin films associated with polarization induced by electrical and mechanical fields.…”

Ferroelectric or non-ferroelectric: Why so many materials exhibit “ferroelectricity” on the nanoscale

“…Piezoelectric response is also seen in PFM studies of a seashell, as seen in (e) Topography, (f) Vertical PFM Amplitude and (g) Phase images. (e-g) are reprinted from Li et al 427 , with the permission of AIP Publishing 223 and (g,h) is from Sharma et al 216 . Hysteresis loops acquired by PFM on BFO nanocapacitors, as a function of the applied AC potential.…”

“…In other cases, alternative mechanisms were considered, such as (but not limited to) examples in the work of Gautier et al 213 , who measured electromechanical response, switching loops and domain retention in amorphous LaAlO3 thin films, Kholkin et al 214,215 (piezoelectric behavior in SrTiO3 ceramics), or Sharma et al 216 (switching behavior in LaAlO3). However, the birds-eye view overview of the published results suggests the remarkable commonality between the observed phenomena.…”

Mechanical force involved multiple fields switching of both local ferroelectric and magnetic domain in a Bi5Ti3FeO15 thin film

“…9,10 Recently, mechanical-force-induced ferroelectric domain switching in multiferroics has been reported by several groups. 11,12,13 It is natural to ask whether such an external mechanical force could switch two or all three types of ferroic domains (ferroelectric, ferroelastic and magnetic domains) in multiferroic materials. Finding the answer in multiferroics is of fundamental and practical importance for understanding their quasistatic and dynamic behavior in multiply controlled devices applications.…”