Interfacial-layer modulation of domain switching current in ferroelectric thin films

Abstract

It is found that the voltage drop across a 170-nm-thick Pb(Zr0.4Ti0.6)O3 film keeps constantly at a well-defined coercive voltage during domain switching, irrespective of the applied voltage and frequency, and that the switching current of domains is reversely proportional to the resistance of loading resistors in the circuit. A simple formalism is derived for the speed of polarization reversal short into a few nanoseconds. The maximum speed of domain switching is limited by the time of compensation charge dissipation via loading resistors in the circuit, instead of reverse domain nucleation and growth. However, in most cases, the switching current decays with time and is thus peaked under different applied voltages, as observed in an 87-nm-thick film. This phenomenon is understood from our work due to the presence of interfacial passive layers that modulate switching current transient through the circuit RC-time constant, besides the consideration of a broad coercive-voltage distribution in a genuine thin film.

Sub‐Picosecond Processes of Ferroelectric Domain Switching from Field and Temperature Experiments

“…[11] Additionally, the voltage drop across ferroelectric thin films during domain switching remains at V c rather than V (V >V c ), and thus, the voltage (V R ) across the total resistance R t in the circuit is V-V c . [28] Therefore, the switching current is V R /R t , and the I sw -V c dependence is more informative than the t 0 -V plot.…”

“…After that, V f is constant with time until t = t w + t s , when the domain switching completes. [28] The appearance of the current plateau is due to the maximum domain-switching current I sw = (V-V c )/R t limited by R t (≠ 0), and a lasting period of domain switching time of t w is required for the completion of domain screening charge flow (the dissipation of 2P s S charge) in the circuit. After the completion of domain switching, the previous capacitor-charging process is rejuvenated until V is fully dropped across C f .…”

Charge Transport in Ferroelectric Thin Films

“…The switching comprises three distinct steps: the nucleation of ferroelectric domains with opposite direction of polarization; the growth of the ferroelectric domains with polarization parallel to the applied electric field (Tagantsev et al, 2002;Shur et al, 2001;Lohse et al, 2001); the compensation of the depolarization field occurring just after the switching is taking place (Jiang et al, 2007). The models proposed for switching considers only the first two steps, which can be very fast (switching times of the order of nanoseconds).…”

The Inlaid Al2O3 Tunnel Switch for Ultrathin Ferroelectric Films

“…A subsequent current plateau then appears, due to the limited maximum switching current by the total resistance R L of all the in-series resistors in the circuit. [20] In the meantime, the voltage drop across the ferroelectric layer increases to a genuine coercive voltage of only the FE layer (V fc ) at time t 0 . During domain switching after t o , the applied voltage of the FE layer is maintained at V fc , and an extra voltage (V appl -V fc ) is applied to R L .…”