Direct hysteresis measurements of single nanosized ferroelectric capacitors contacted with an atomic force microscope

Abstract

Direct hysteresis measurements on single submicron structure sizes were performed on epitaxial ferroelectric Pb(Zr,Ti)O3 thin films grown on SrTiO3 with La0.5Sr0.5CoO3 (LSCO) electrodes. The samples were fabricated by focused-ion-beam milling resulting in pad sizes down to 200 nm×200 nm. The influence of parasitic capacitance of the measurement setup was eliminated by applying an enhanced compensation procedure. No size effects were observed in capacitors milled down to 400 nm×400 nm. Thus, a published increase of Pmax1 for decreasing pad size can be explained by the parasitic influence of the setup. Finally, the inaccuracy of increasing coercive voltage due to the coating of the cantilever of the atomic force microscope is discussed.

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

“…The measured signal at each point can then be represented as a local on-field and/or off-field hysteresis loop, containing information on local ferroelectric properties and their evolution with bias. After the introduction by Hidaka et al, 156 this technique was rapidly adopted by the community and extensively used to study polarization switching and spatial variations of ferroelectric behavior in PZT, 59,133,134,157,158 BaTiO3, 159,160 Pb0.76Ca0.24TiO3, 161 and more.…”

Piezoresponse Force Microscopy Studies of Switching Behavior of Ferroelectric Capacitors on a 100-ns Time Scale

“…A major limitation in acquiring this crucial information is the lack of experimental methods to characterize the domain kinetics in ferroelectric thin films [12,13]. The lateral dimensions of the ferroelectric capacitors in FeRAM devices are in the micrometer range with the switching times measuring well below 100 ns [14,15], which requires testing of domain switching behavior with the nanometer spatial and nanosecond time resolutiondone for the first time in this Letter. In the absence of such local data, only rudimentary attempts have been made to develop microscopic switching models in finite-size structures [16,17].…”

Shear effects in lateral piezoresponse force microscopy at 180° ferroelectric domain walls

“…Although quantitative measurements of piezoelectric coefficients via PFM are challenging, the technique has provided valuable information about the behavior of domain walls and switching dynamics both in thin films 7,8 and in device structures. [9][10][11] In this context, understanding the origins of the PFM signal observed at ferroelectric domain walls is an important issue.Considering only piezoelectric effects, in a c-axis-oriented tetragonal ferroelectric film with an electric field applied along the polarization axis, the piezoelectric response is determined by the d 33 coefficient, leading to a purely vertical PFM signal. However, in such films, a nonzero lateral PFM response has been observed specifically at the position of 180°domain walls.…”

“…Although quantitative measurements of piezoelectric coefficients via PFM are challenging, the technique has provided valuable information about the behavior of domain walls and switching dynamics both in thin films 7,8 and in device structures. [9][10][11] In this context, understanding the origins of the PFM signal observed at ferroelectric domain walls is an important issue.…”