Materials World Network: Transport, Switching and Size Effects in the Lead-Free Ferroelectric, BiFeO3

材料世界网络：无铅铁电材料 BiFeO3 中的输运、转换和尺寸效应

• 批准号: 0603204
• 负责人: Ramamoorthy Ramesh
• 金额: $ 45万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-15 至 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0603204&HistoricalAwards=false
• 关键词: Materials; World; Network; Transport; Switching

This research explores fundamental nanoscale phenomena in artificially and spontaneously engineered multicomponent oxide heterostructures. The work involves extensive collaboration between researchers at the University of California, Berkeley under Professor Ramamoorthy Ramesh and at RWTH Aachen under the guidance of Professor Rainer Waser. Ferroelectric thin films have attracted considerable interest as functional materials for a variety of microelectronic applications. They possess a wide range of physical responses, including the existence of spontaneous polarization (useful in memories) large piezoelectric responses (useful in MEMS devices). In recent years, considerable progress has been made in the integration of thin films of prototypical ferroelectrics such as lead zirconate titanate (PZT) and strontium bismuth titanate (SBT) with Si based electronics to enable the first generation of nonvolatile memories (FRAMS). The recent concerns with the toxicity of lead in PZT have fueled the search for alternative material systems. This research is focused on understanding the structure property relationships in the new family of multiferroic ferroelectrics, BiFeO3, using the combined expertise in the two institutions. The first set of problems concerns the exploration of fundamental size scaling effects in these thin films and the second is a comprehensive understanding of the nanoscale dynamical phenomena that impact the functionality of these materials. This work seeks to impact this very topic through a combination of advanced materials processing approaches, incorporation of state-of-the-art nanolithography tools (such as focused ion beam milling and e-beam lithography) to create the nanostructures and the use of a variety of probes to study and understand dynamical (i.e., time-dependent) physical phenomena at the nanoscale. Investigations to be carried out include correlated conductivity and domain mapping using scanning probe microscopy, dynamic switching studies, piezoelectric characterization. BiFeO3 simultaneously exhibits anti-ferromagnetic as well as ferroelectric properties. Due to the fact that the ferroelectric properties are pronounced in form of a high remnant polarization and high Curie temperature, this research emphasizes the ferroelectric part. The high remnant polarization on the order of 90C/cm2, together with the absence of lead, makes this material very attractive for applications in ferroelectric non-volatile memories and mechanical-electrical micro/nano systems. Many open questions still remain before BiFeO3 can find its way into various products. This work concentrates on the most important issues, including the scaling of BiFeO3 into ultrathin films and nano-sized lateral structures. Doping is considered as a way to reduce the relative high coercive filed of BiFeO3 and lower the leakage current. Novel experiments in a close collaboration with the Advanced Light Source at the Berkeley Lab will be performed in which the atomic structure as well as the electrical characteristics are investigated at the same time.The proposed collaboration between the University of California, Berkeley and researchers at Aachen is of potential mutual benefit. Aachen contributes its highly advanced device processing capabilities, the scanned probe characterization will be accomplished at Berkeley. In addition, both institutions have very strong computational and theoretical modeling expertise as well.

这项研究探讨了人工和自发工程多组分氧化物异质结构的基本纳米现象。 这项工作涉及研究人员在加州大学伯克利分校教授Ramamoorthy Ramesh和RWTH亚琛教授Rainer Waser的指导下进行的广泛合作。 铁电薄膜作为功能材料在微电子领域有着广泛的应用前景。 它们具有广泛的物理响应，包括存在自发极化（在存储器中有用）和大的压电响应（在MEMS设备中有用）。近年来，原型铁电体薄膜如锆钛酸铅（PZT）和钛酸锶铋（SBT）与硅基电子器件的集成已经取得了相当大的进展，以实现第一代非易失性存储器（FRAMS）。 最近对PZT中铅的毒性的关注推动了对替代材料系统的研究。 本研究的重点是了解结构的多铁性铁电体，BiFeO 3的新家庭的性质关系，利用这两个机构的专业知识相结合。第一组问题涉及探索这些薄膜中的基本尺寸缩放效应，第二组问题是对影响这些材料功能的纳米级动力学现象的全面理解。这项工作旨在通过先进的材料加工方法的组合，结合最先进的纳米光刻工具（如聚焦离子束铣削和电子束光刻）来创建纳米结构，并使用各种探针来研究和理解动态（即，时间依赖的）纳米级的物理现象。要进行的调查，包括相关的电导率和域映射使用扫描探针显微镜，动态切换研究，压电特性。BiFeO 3同时具有反铁磁和铁电性质。由于铁电性质以高剩余极化和高居里温度的形式突出，因此本研究强调铁电部分。90 C/cm 2量级的高剩余极化，加上不含铅，使得这种材料在铁电非易失性存储器和机电微/纳米系统中的应用非常有吸引力。在BiFeO 3能够进入各种产品之前，仍然存在许多悬而未决的问题。这项工作集中在最重要的问题，包括缩放的BiFeO 3成纳米薄膜和纳米尺寸的横向结构。掺杂被认为是降低BiFeO_3的相对高的矫顽场和降低漏电流的一种方法。与伯克利实验室的先进光源密切合作，将进行新的实验，同时研究原子结构和电学特性。加州大学伯克利分校和亚琛研究人员之间拟议的合作具有潜在的互利性。 亚琛贡献其高度先进的设备处理能力，扫描探针表征将在伯克利完成。此外，这两个机构都拥有非常强大的计算和理论建模专业知识。