Hierarchy of domain reconstruction processes due to charged defect migration in acceptor doped ferroelectrics

Abstract

UkraineEvolution of a stripe array of polarization domains triggered by the oxygen vacancy migration in an acceptor doped ferroelectric is investigated in a self-consistent manner. A comprehensive model based on the Landau-Ginzburg-Devonshire approach includes semiconductor features due to the presence of electrons and holes, and effects of electrostriction and flexoelectricity especially significant near the free surface and domain walls. A domain array spontaneously formed in the absence of an external field is shown to undergo a reconstruction in the course of the gradual oxygen vacancy migration driven by the depolarization fields. The charge defect accumulation near the free ferroelectric surface causes a series of phenomena: (i) symmetry breaking between the positive and negative cdomains, (ii) appearance of an effective dipole layer at the free surface followed by the formation of a surface electrostatic potential, (iii) tilting and recharging of the domain walls, especially pronounced at higher acceptor concentrations. An internal bias field determined by the gain in the free energy of the structure exhibits dependences of its amplitude on time and dopant concentration well comparable with available experimental results on aging in BaTiO 3 . † Corresponding

In-situ monitoring of interface proximity effects in ultrathin ferroelectrics

“…Similarly, cationic vacancies were reported to affect the PTO polarization orientation 25 . Furthermore, the observed time for the reconstruction of polarization (ii) of about 10 2 s matches the theoretically derived value in response to ion migration 26 . Most importantly, the post-growth surface-sensitive angle-resolved XPS data shown in Fig.…”

The interaction between vacancies and twin walls, junctions, and kinks, and their mechanical properties in ferroelastic materials

“…Several experimental studies have been carried out to understand the effect of vacancies on the motion of TBs in BiFeO3 with acceptor-oxygen-vacancy defect pairs [20], the mineral anorthoclase and a general case of ferroelastic walls with vacancies [21][22][23], in particular the memory effect of TBs due to pinning effect. A few simulations were performed to study this effect for perovskite structures [24][25][26][27][28]. Meanwhile, the vacancies could also act as nucleation sites for domain switching [29].…”

Exploring Charged Defects in Ferroelectrics by the Switching Spectroscopy Piezoresponse Force Microscopy

“…In ferroelectric materials, precise control of the polarization reversal and hysteresis behavior at the nanoscale is prerequisite for many applications, such as under electric field. [18,21,22] In macroscopic measurements, charged defects manifest themselves as a shift of polarization versus electric field hysteresis loops, termed "bias field" or "imprint," [23][24][25][26] and in ferroelectric hysteresis loop doubling or "pinching." [17,[27][28][29][30] Accumulation of charged defects at the domain walls and grain boundaries has been proven experimentally in bismuth ferrite by scanning transmission electron microscopy and conductive atomic force microscopy measurements.…”

“…[13] The optical method of second harmonic generation can be used to monitor the defect concentration and off-stoichiometry, [16] however it is limited in resolving the type of charged defects and yields only micrometer-scale spatial resolution. Thus, the novel experimental approaches allowing accurate measurement of the defect concentration and/or corresponded functional properties at the nanoscale are highly desirable.In ferroelectrics, charged defects affect polarization reversal as they directly participate in the screening of the depolarization electric field [8,[17][18][19][20] since they can become mobile Monitoring the charged defect concentration at the nanoscale is of critical importance for both the fundamental science and applications of ferroelectrics. However, up-to-date, high-resolution study methods for the investigation of structural defects, such as transmission electron microscopy, X-ray tomography, etc., are expensive and demand complicated sample preparation.…”

“…In ferroelectrics, charged defects affect polarization reversal as they directly participate in the screening of the depolarization electric field [8,[17][18][19][20] since they can become mobile Monitoring the charged defect concentration at the nanoscale is of critical importance for both the fundamental science and applications of ferroelectrics. However, up-to-date, high-resolution study methods for the investigation of structural defects, such as transmission electron microscopy, X-ray tomography, etc., are expensive and demand complicated sample preparation.…”