Nanoscopic studies of domain structure dynamics in ferroelectric La:HfO2 capacitors

Abstract

Visualization of domain structure evolution under an electrical bias has been carried out in ferroelectric La:HfO2 capacitors by a combination of Piezoresponse Force Microscopy (PFM) and pulse switching techniques to study the nanoscopic mechanism of polarization reversal and the wake-up process. It has been directly shown that the main mechanism behind the transformation of the polarization hysteretic behavior and an increase in the remanent polarization value upon the alternating current cycling is electrically induced domain de-pinning. PFM imaging and local spectroscopy revealed asymmetric switching in the La:HfO2 capacitors due to a significant imprint likely caused by the different boundary conditions at the top and bottom interfaces. Domain switching kinetics can be well-described by the nucleation limited switching model characterized by a broad distribution of the local switching times. It has been found that the domain velocity varies significantly throughout the switching process indicating strong interaction with structural defects.

Recent Progress in the Nanoscale Evaluation of Piezoelectric and Ferroelectric Properties via Scanning Probe Microscopy

“…In addition, if pulses can be applied with different pulse widths and voltages without scanning the surface (instead of box patterns), a more detailed switching behavior under different pulse conditions can be explored. [19,110,119,120,[123][124][125][126][127][128][129] The advantage of the PFM imaging mode is that the local domain structure and domain motion can be easily visualized. Thus, if similar measurements are conducted in ferroelectric capacitors as a function of the pulse conditions, it is feasible to explore the switching dynamics in the structure of the ferroelectric capacitor using PFM by analyzing the switched area.…”

“…Thus, if similar measurements are conducted in ferroelectric capacitors as a function of the pulse conditions, it is feasible to explore the switching dynamics in the structure of the ferroelectric capacitor using PFM by analyzing the switched area. [18,19,123,127,129,130] In general, it is not physically straightforward for the PFM imaging mode combined with the poling procedure to provide complete information on switching parameters, such as the coercive voltage and magnitude of the remnant piezoresponse; this is because the process requires extensive scanning at different pulse conditions. Such information can be conveniently explored with the PFM spectroscopy mode.…”

Nanoscale Probing of Ferroelectric Domain Switching Using Piezoresponse Force Microscopy

“…33) Based on this inhomogeneous nucleation, the stroboscopic method has been applicable to many ferroelectric capacitors. 33,[35][36][37] The domain tracing method is the approach used to focus on the acquisition of PFM images for a single switching process. Even if inhomogeneous nucleation occurs, the nucleation process still has a stochastic nature, i.e., nucleation probability is not 100%.…”

Piezoelectric Response of Polycrystalline Silicon‐Doped Hafnium Oxide Thin Films Determined by Rapid Temperature Cycles

“…Piezoelectric properties of the material have been studied using piezo‐force microscopy17,18 (PFM) and double beam laser interferometry19 (DBLI). However, these studies focus on the out‐of‐plane response e 33 .…”

“…[9] Stabilization of the polar phase is most commonly achieved by doping, [10] where Al, [11] La, [12] Si, [13] Zr, [14] and Y [15] are often used. As a range of energetically close polymorphs exists, [16] HfO 2 films mostly are poly crystalline, consisting of a phase mixture with orthorhombic, tetragonal, monoclinic, and cubic grains.Piezoelectric properties of the material have been studied using piezo-force microscopy [17,18] (PFM) and double beam laser interferometry [19] (DBLI). However, these studies focus on the out-of-plane response e 33 .…”