界面偶极子增强铁电隧道结电致电阻效应的研究

Memory based on ferroelectric tunnel junctions (FTJs) with characteristics of high-storage density, high read/write speed, random access, non-volatility, low-power consumption and highly integration becomes a powerful competitor in the highly integrated chip systems. In this project, to obtain giant tunnel electroresistance (TER) effect under bi-stable polarization switchable of ferroelectric tunnel barrier, we propose a theory and method to enhance the TER ratio of FTJs by artificial interface dipoles. In the case, perovskite type-BaTiO3 (BTO) ferroelectric is selected for the tunneling barrier, and SrRuO3 (SRO) is bottom electrode. For the ionized layers, (LaO)+ and (AlO2)- are created by depositing just a few unit cells (0-2 u.c.) of either LaTiO3 or SrAlOx between the electrode and ferroelectric barrier which can form so called artificial interface dipole. All samples are fabricated by laser molecular beam epitaxy (L-MBE) with high pressure reflection high energy electron diffraction (RHEED). The relation between ferroelectric polarication, electroresistance behavior and artificial interface dipoles is studied. Furthermore, the mechanism of enhancing the TER ratio of FTJs by artificial interface dipoles is analyzed by experiment and calculation. The internal relation between the key performance parameters and interface microstructure of material is established by studying structure-growth-performance-theoretical authentication.

铁电隧道结存储器具有高存储密度、高读/写速度、随机存取、非易失性、低能耗和集成度高等特点，是高集成度芯片系统中非易失存储器的有力竞争者。本项目着眼于保持铁电阻挡层极化反转状态稳定的前提下获得巨大的隧穿电致电阻效应以提高信号的输出水平，提出通过人工界面偶极子增强铁电隧道结电致电阻效应的设计理论及方法。为此，拟选用钙钛矿铁电体BaTiO3为隧穿阻挡层，SrRuO3为底电极，在电极与铁电薄膜界面处插入小于2u.c.的LaTiO3或SrAlOx获得(LaO)+或(AlO2)-离子层形成 “人工界面偶极子”。采用激光分子束外延(L-MBE)技术结合反射高能电子衍射仪(RHEED) 制备相应外延超薄膜。系统研究铁电极化、电致阻变特性与界面偶极子的标度行为，并探索人工界面偶极子增强铁电隧道结电致电阻效应的机理。通过材料结构-生长-性能-理论验证的相关联性，建立材料界面微结构与关键性能参数之间的内在联系。

铁电隧道结存储器具有高存储密度、高读/写速度、随机存取、非易失性、低能耗和集成度高等特点，是高集成度芯片系统中非易失存储器的有力竞争者。本项目着眼于保持铁电阻挡层极化反转状态稳定的前提下获得巨大的隧穿电致电阻效应以提高信号的输出水平，提出通过人工界面偶极子增强铁电隧道结电致电阻效应的设计理论及方法。为此，选用钙钛矿铁电体BaTiO3为隧穿阻挡层，SrRuO3为底电极，在电极与铁电薄膜界面处插入小于2u.c.的LaTiO3获得(LaO)+离子层形成 “人工界面偶极子”。采用激光分子束外延(L-MBE)技术结合反射高能电子衍射仪(RHEED) 制备相应外延超薄膜。系统了研究铁电极化、电致阻变特性与界面偶极子的标度行为，并探索了人工界面偶极子增强铁电隧道结电致电阻效应的机理。通过材料结构-生长-性能-理论验证的相关联性，建立了材料界面微结构与关键性能参数之间的内在联系。通过本项目的研究，制备出了高质量的超薄外延异质结铁电薄膜；揭示了界面偶极子对材料性能调控的规律；优化工艺，获得了巨电致阻变效应TER>10^6。提出了采用人工界面偶极子来增强铁电隧道结电致电阻效应，为铁电材料用于非易失性存储器提供了新的思路。