Imprint in Ferroelectric Capacitors

Abstract

We show that voltage offsets in the polarization-voltage characteristics of Pb(Zr, Ti)O3 capacitors can lead to imprint in ferroelectric memory devices. The thermal-induced voltage shifts (internal bias field) are in part attributed to the role of oxygen vacancy-related defect dipoles throughout the film. In support of this, it is found that donor doping at the Ti(Zr) sites reduces the thermally-induced voltage shifts. The stress-induced voltage shifts are found to be dependent on the Zr/Ti cation ratio. This compositional dependence is explained by considering the role of deep bulk Ti3+ centers and/or a compositional dependent oxygen vacancy density.

Mechanisms of imprint effect on ferroelectric thin films

“…Warren et al have already demonstrated that ionic defects, such as oxygen vacancies produced by reducing treatment, are responsible for ferroelectric domain pinning and formation of nonswitching layers, which shifts the hysteresis loops horizontally. 6 We propose that nonswitching layers may be formed by lattice misfit stress or by electronic charge trapping at domain boundaries, leading to the occurrence of imprint. By treating some layers near the bottom electrode as graded surface layers induced by some degradation mechanisms, our simulation successfully reproduced the large horizontal shifting of hysteresis loops observed in experiments.…”

“…Warren et al 6 attributed the occurrence of imprint to defect dipoles related to oxygen vacancies. Abe and coworkers assumed a nonswitching layer between the ferroelectric layer and the bottom electrode, which is possibly formed by the relaxation of lattice misfit strain in the heteroepitaxial ferroelectric thin film.…”

Fatigue effect in ferroelectric PbZr1−xTixO3 thin films

“…The most important mechanisms are fatigue 1 and imprint. 2 In this paper, sputtered PZT thin films were investigated especially in the eye of fatigue. Fatigue is commonly known as the loss of polarization of a hysteresis loop due to an increasing number of bipolar switching cycles.…”

Усиление И Инверсия Переменного Электрического Поля В Мелкодисперсном Диэлектрике

“…С использованием метода Сойера−Тауэра (см., на-пример, [6,7]) на цифровом осциллографе Hantek DSO 2150 USB измерялись петли диэлектрического гистере-зиса образцов на частотах ν = 20−10 3 Hz. Для этого использовался емкостный делитель напряжения в виде последовательно соединенных измерительного и эта-лонного конденсаторов.…”