Ferroelectric Nanotubes

We report the independent invention of ferroelectric nanotubes from groups in several countries. Devices have been made with three different materials: lead zirconate-titanate PbZr1-xTixO3 (PZT); barium titanate BaTiO3; and strontium bismuth tantalate SrBi2Ta2O9 (SBT). Several different deposition techniques have been used successfully, including misted CSD (chemical solution deposition) and pore wetting. Ferroelectric hysteresis and high optical nonlinearity have been demonstrated. The structures are analyzed via SEM, TEM, XRD, AFM (piezo-mode), and SHG. Applications to trenching in Si dynamic random access memories, ink-jet printers, and photonic devices are discussed. Ferroelectric filled pores as small as 20 nm in diameter have been studied

Механизмы формирования гетерофазных сегнетоэлектрических пленок цирконата-титаната свинца

An experimental and theoretical study of the formation processes of "impurity" phase inclusions in ferroelectric oxides is carried out via example of polycrystalline lead zirconate-titanate (PZT) films. A feature of these compositions is relatively high volatility of lead oxides, which can lead to deficiency of these components in the composition of the ferroelectric film formed during high-temperature crystallization. To avoid lead losses, some excess is added to the solution in the process of synthesis. Experimental samples of PZT films are obtained using sol-gel method with different contents of lead oxide, the crystallization of the ferroelectric phase of the films is carried out in air at 600 °C. In the films, the inclusions of lead oxide impurity phase are found, and the size distribution of these inclusions are obtained. Model concepts are presented and a system of equations is proposed describing the dispersed inclusions formation kinetics of new phases of different stoichiometric composition at the interfaces in polycrystalline films of multicomponent ferroelectric oxides due to bulk diffusion and grain-boundary segregation. Comparison of the experimental data with the theoretical model gives qualitative agreement. The approach generality makes it possible to extend the model to other systems of multicomponent ferroelectric polycrystalline materials.Проведено экспериментальное и теоретическое изучение процессов образования включений "примесных" фаз в сегнетоэлектрических оксидах на примере поликристаллических пленок цирконата-титаната свинца (ЦТС). Особенностью данных составов является сравнительно высокая летучесть оксидов свинца, что может приводить к дефициту этих компонентов в составе формируемой сегнетоэлектрической пленки в ходе высокотемпературной кристаллизации. Чтобы избежать потери свинца, в процессе синтеза в раствор добавляют его некоторый избыток. Экспериментальные образцы пленок ЦТС были получены золь-гель-методом с различным содержанием оксида свинца, кристаллизация сегнетоэлектрической фазы пленок осуществлялась на воздухе при температуре 600 °C. В пленках обнаружены включения примесной фазы оксида свинца, получено распределение включений по размерам. Изложены модельные представления и предложена система уравнений, описывающие кинетику образования дисперсных включений новых фаз различного стехиометрического состава на границах раздела в поликристаллических пленках многокомпонентных сегнетоэлектрических оксидов за счет процессов объемной диффузии и зернограничной сегрегации. Сопоставление экспериментальных данных с теоретической моделью дало согласие на качественном уровне. Общность подхода позволяет распространить модель на другие системы многокомпонентных сегнетоэлектрических поликристаллических материалов

Dead layer thickness estimation at the ferroelectric film-metal interface in PZT

Yu. Podgorny acknowledges the program of Ministry of Education and Science (3.5726.2017/8.9) and K. Vorotilov and A. Sigov thank the program of Ministry of Education and Science (11.2259.2017).Different models for estimation of the dead layer thickness at the ferroelectric film-metal interface are discussed, including the small-signal capacitance model and two methods based on dielectric hysteresis analysis—one based on slopes of the hysteresis loops at the coercive field and the other method based on comparison of dielectric hysteresis portraits. It is shown that the latter technique yields more reliable data as it excludes the effect of leakage and relaxation loss. Conductivity may have a pronounced effect on the validity of dead-layer thickness data. This work relates peripherally to negative capacitance in ferroelectric films and to lozenge-shaped hysteresis curves.Publisher PDFPeer reviewe

Nonlinear-optical and micro-raman diagnostics of thin films and nanostructures of ABO(3) ferroelectrics

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