Thickness dependence of intrinsic dielectric response and apparent interfacial capacitance in ferroelectric thin films

Abstract

We studied theoretically the influence of the progressive strain relaxation and the depolarizing-field effect on the thickness dependence of the out-of-plane dielectric response of epitaxial ferroelectric thin films sandwiched between extended metal electrodes. The calculations show that the inverse of the measured capacitance varies with the film thickness almost linearly in the most part of the thickness range at the majority of temperatures. Extrapolation of this linear dependence to zero thickness usually gives considerable nonzero intercept even in the absence of nonferroelectric interfacial layers. Remarkably, such apparent “interfacial capacitance” in a certain temperature range becomes negative. The physical meaning of the effective dielectric constant, which can be extracted from the slope of the reciprocal capacitance thickness dependence, is also analyzed. The theoretical predictions are compared with the experimental data obtained for single-crystalline SrRuO3∕Ba0.7Sr0.3TiO3∕SrRuO3 and Pt∕Ba0.7Sr0.3TiO3∕SrRuO3 thin-film capacitors.

Hyper-sensitive piezophotovoltaic effects in ferroelectric nanocylinders

“…of the top and bottom interfaces. 8,30,32,[57][58][59][60][61] In the present work, the extrapolation lengths of the top and bottom interface are same, i.e., ␦ I-T = ␦ I-B = ␦ I . 61 Note that ␦ I-T and ␦ I-B have different physical origins, such as different topbottom electrodes, interface effect and polarization switching etc., which may be obtained from first-principle calculations 8,52,55 and a combination of first-principle and phenomenological calculations.…”

“…The second component is more complex and is determined by several factors, including space and surface charges, the small size effect, interface effect or Schottky barriers etc. 8,[27][28][29][30][31][32]46,[57][58][59][60][61] The effects of the surface and interface on the profile of the depolarization field in the FNC and FTF have been discussed in previous works. 34,35,42,53 In general, the profile of the depolarization field is nonuniform near the interfaces, and can be opposite to those at the center of the FNC and FTF.…”

Understanding the origins of the intrinsic dead layer effect in nanocapacitors

“…Indeed early experimental work by Mead 2,3 and subsequently many others [4][5][6][7] have documented the effects of the disruptive dead-layer for nanometer sized films. The presence of this dead layer is attributed to a variety of reasons including a secondary low-permittivity phase at the surface of the films, nearbysurface variation of polarization (field induced or spontaneous) 8 , presence of misfit dislocations 9,10 , electric field penetration into the metal electrodes [11][12][13][14] among others. The effect of electric field penetration into the metal electrodes to explain the anomalous capacitance was proposed by Mead 2 himself and has since then been theoretically investigated by several authors [11][12][13][14] .…”

“…The presence of this dead layer is attributed to a variety of reasons including a secondary low-permittivity phase at the surface of the films, nearbysurface variation of polarization (field induced or spontaneous) 8 , presence of misfit dislocations 9,10 , electric field penetration into the metal electrodes [11][12][13][14] among others. The effect of electric field penetration into the metal electrodes to explain the anomalous capacitance was proposed by Mead 2 himself and has since then been theoretically investigated by several authors [11][12][13][14] . Recent pioneering ab initio calculations by Stengel and Spaldin 15 on SrRuO 3 /SrTiO 3 /SrRuO 3 and Pt/SrTiO 3 /Pt thin film capacitors with atomistically smooth interfaces (to exclude effects due to, say, misfit dislocations) have confirmed the intrinsic nature of this effect and that electric field penetration occurs in real metal electrodes giving rise to a passive dead layer at the metal-dielectric interface.…”

Термостабильные Сегнетоэлектрические Конденсаторы На Основе Градиентных Пленок Титаната Бария-Стронция

“…Для оценки стабилизации емкости в многослойных конденса-торах может быть использована математическая модель, суть которой состоит в аппроксимации эксперименталь-ной зависимости емкости C от температуры T по закону Кюри−Вейса, с учетом плотности емкости переходного слоя между электродом и СЭ пленкой. Переходной слой ( " мертвый слой"), обусловленный несоответствием структурных параметров СЭ пленки и электрода, фи-зически может быть интерпретирован как слой, не об-ладающий сегнетоэлектрическими свойствами [19,20], а математически обеспечивает возможность определения величины расчетной емкости в точке перехода, а также размытие перехода в диапазоне температур.…”