Interfacial dielectric layer as an origin of polarization fatigue in ferroelectric capacitors

Abstract

Origins of polarization fatigue in ferroelectric capacitors under electric field cycling still remain unclear. Here, we experimentally identify origins of polarization fatigue in ferroelectric PbZr0.52Ti0.48O3 (PZT) thin-film capacitors by investigating their fatigue behaviours and interface structures. The PZT layers are epitaxially grown on SrRuO3-buffered SrTiO3 substrates by a pulsed laser deposition (PLD), and the capacitor top-electrodes are various, including SrRuO3 (SRO) made by in-situ PLD, Pt by in-situ PLD (Pt-inPLD) and ex-situ sputtering (Pt-sputtered). We found that fatigue behaviour of the capacitor is directly related to the top-electrode/PZT interface structure. The Pt-sputtered/PZT/SRO capacitor has a thin defective layer at the top interface and shows early fatigue while the Pt-inPLD/PZT/SRO and SRO/PZT/SRO capacitor have clean top-interfaces and show much more fatigue resistance. The defective dielectric layer at the Pt-sputtered/PZT interface mainly contains carbon contaminants, which form during the capacitor ex-situ fabrication. Removal of this dielectric layer significantly delays the fatigue onset. Our results clearly indicate that dielectric layer at ferroelectric capacitor interfaces is the main origin of polarization fatigue, as previously proposed in the charge injection model.

Hafnium Oxide (HfO2) – A Multifunctional Oxide: A Review on the Prospect and Challenges of Hafnium Oxide in Resistive Switching and Ferroelectric Memories

“…They behave as a transparent medium preventing the accumulations of oxygen vacancies at the metal-electrode interface, capable of causing serious issues for device operation (fatigue). [356] Moreover, the formation of an insulating interfacial layer with the oxygen-metal reaction, which causes incomplete screening of polarization charges, can create depolarizing field against ferroelectric polarization. [248] This field can directly cause a reduction in the net polarization and indirectly cause the injection of electrons from metal electrodes inside the insulating film, which degrades ferroelectric polarization under cycling field.…”

“…[357,358] Capacitors with conductive oxide electrodes such as SrRuO 3 , LaNiO 3 , LaSrMnO 3 , IrO 2 , LaSrCaO 3 , YBa 2 Cu 3 O x , and RuO 2 are generally free from fatigue. [356] In contrast, capacitors with conventional metal electrodes such as Pt and Au are strongly fatigued. [356] Do et al [356] asserted that oxygen vacancies migrate and accumulate at the capacitor interfaces during field cycling, subsequently causing domainwall pinning and polarization screening, which can lead to polarization fatigue.…”

“…[356] In contrast, capacitors with conventional metal electrodes such as Pt and Au are strongly fatigued. [356] Do et al [356] asserted that oxygen vacancies migrate and accumulate at the capacitor interfaces during field cycling, subsequently causing domainwall pinning and polarization screening, which can lead to polarization fatigue. [356] They assumed metal electrodes to block the migration of oxygen vacancies, resulting in a significant accumulation of these defects at the capacitor interfaces and leading to pronounced fatigue.…”

Relaxor-Ferroelectric Films for Dielectric Tunable Applications: Effect of Film Thickness and Applied Electric Field

“…If C P is the capacitance due to the PLZT film and C i is the interfacial capacitance between film and electrode, the effective (measured) capacitance ( C eff ) can be given as [ 69 , 70 ]: Equation (6) can be then expresses as follow: where A is the surface area of top-electrode, and t and t i are the total film thickness and the interfacial layer thickness, respectively. ε P and ε i are the dielectric constant of PLZT and interfacial layers, respectively.…”

Layer growth and hysteresis modelling of epitaxial lead zirconate titanate thin films

“…The second model considers the interfacial layer injecting electrons to the ferroelectric layer, leading to decomposition of the ferroelectric layer. [76][77][78][79] Existence of such an interfacial layer in the PLD PZT films has been recently proven using TEM measurements [80]. To make a fair comparison of the influence of the template layer to the ferroelec-tric properties, we compare the P-E and I-E loops of all samples in the woken-up state, where the P r is maximum in Fig.…”