镍锰酸铋基多铁薄膜场致介电响应机理及其忆阻器效应研究

It was not yet clear that which intrinsic phyaical mechamism of nonlinear dielectric response and memristor effect in antiferroelectric multiferroic thin films based Bi2NiMnO6(BNMO). Recently, we have interest in the dielectric response and resistuve switching behaviors induced by an electric field, and discovered ferroelectrity-related phenomena, the colossal dielectric tunability and giant electrode effect on tunneling electroresistance in multiferroic BNMO thin films. However, annealing atmosphere effect on the oxygen vacancies concentration in the samples, it is noticed that the colossal dielectric tunability in our previous works mainly appear at the vicinity of zero electric field, which limits the commercial application of the dielectric tunable devices. In fact, the colossal dielectric tunability over a broad temperature (or electric field) range is very important for exploiting the commercial microwave devices. In this research project, based on the domain switching tuned by the strain in double perovskite multiferroic thin films, the mechanism of the broad temperature (or electric field) dielectric tunable by the strain will be studied. On the one hand, there are diode effect, unipolar/bipolar resistive switching and memristor effect exist in the heterostructure BNMO/LaNiO3 thin films based on the influence of asymmetric electrode on the resistive switching characteristics of the heterostructure thin films. Resistive switching in multiferroic heterostructure has attracted immense interest due to its potertial use in nanoelectronic devices. The phenomena related the interface of the films-electrodes and oxygen vacancies in the films. On the one hand, the epitaxial multiferroic thin films will be prepared by using magnetron sputtering, and reduced leakage current by selected the various bottom electrode and buffer layers. Finally, based on the experiment and theory analysis of the asymmetric electrode and domain switching in the thermodynamic Landau-Ginzburg-Dovenshire (LGD) framework, the physical mechanism of the relation of the colossal dielectric tunability and the giant electrode effects will be studied.

镍锰酸铋基双钙钛矿反铁电多铁性薄膜的非线性介电响应与忆阻器效应，其内在的物理机制尚不够清晰。申请人关注于电致介电响应与阻变的应变调控，在前期发现镍锰酸铋具有巨介电调谐率与巨电极效应。通过样品制备条件的调控，我们聚焦于氧空位在电场作用下氧空位扩散，当外加电场升高时，导致其介电常数急剧降低，进而出现双平台现象，限制了其应用。本申请项目将从掺杂与应变调控的角度探索宽域巨介电调谐效应的实现方法与产生机理。在样品非对称电极导致的巨电极效应的分析中，我们确认镍锰酸铋基薄膜的二极管效应、单极电阻开关效应、双极电阻开关或忆阻器效应，与薄膜的氧空位及电极/薄膜界面密切相关，具有应用价值。进一步研究还表面，选择不同的底电极或过渡层，可以降低漏电流。本项目拟在此基础上结合上下电极和平面电极的不同选择，多角度验证氧空位在巨介电响应、巨电极效应调控中的作用方式，以及调节界面载流子传导机制，从理论上解释其关联。

研究Bi2NiMnO6(BNMO) 双钙钛薄膜的场致介电响应与介电调谐特性，试验发现单斜相BNMO双钙钛矿薄膜结构可以通过应变调控，从单斜相相结构到六角相相。研究了单斜相BNMO薄膜的电场诱导下的介电响应，氧气氛退火BNMO薄膜的介电调谐率均高达75%至78%；如在1MHz情况下，650℃氮气氛退火BNMO薄膜样品在低压就可以实现介电调谐率为88%至89%。BNMO 薄膜具有高介电调谐率与优质因子，在微波调谐器件方面有应用前景。.研究了BNMO、Bi2FeMnO6与Bi2FeCrO6双钙钛薄膜忆阻器特性与铁电二级管特性。可以通过应变调控其相结构从单斜相到六角相，并实现六角相择优取向生长，从而改善BNMO铁电薄膜二级管特性，二极管温度稳定性良好。Bi2FeMnO6与Bi2FeCrO6薄膜均为菱方相结构，具有铁电二级管特性与光伏特性，并从第一性原理计算解释其机制。. 结合SrTiO3基陶瓷与薄膜的阻变特性，我们认为SrTiO3基薄膜阻变特性，主要来自氧缺陷。特别是RP结构SrTiO3基薄膜，非晶薄膜因为氧缺陷多阻变性能好，高温退火的薄膜因结晶、缺陷减少，阻变特性反而不如非晶薄膜。这为非晶RP结构SrTiO3基薄膜阻变存储器的应用提供新思路。试验发现金属氧化薄膜、薄膜异质结的忆阻器特性，与基片、顶电极和底电极、异质结的上下顺序等等联系紧密。不论是金属薄膜忆阻器、二级管，还是铁电薄膜二级管，都可以通过应变/应力调控、缺陷密度设计，可得到高/低组态比高的性能优异的薄膜阻变存储器器件。. 研究发现，钛酸钡与钛酸铅基陶瓷具有巨电卡效应(1.64K~1.67K)。非化学剂量比(Pb,La)(Zr,Ti)O3(PLZT)陶瓷具有巨电卡效应(-12.45K)、PLZT-BiFeO3复合陶瓷的的电卡效应更好(-17.8K)。在电卡致冷方面有应用前景。