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Incipient ferroelectrics based on hafnium oxide

基于氧化铪的早期铁电体

基本信息

批准号：
226260235
负责人：
Dr.-Ing. Ulrich Böttger
金额：
--
依托单位：
Institut für Halbleiter- und Mikrosystemtechnik (IHM)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/226260235?language=en
关键词：
Incipient ferroelectrics based hafnium oxide

项目摘要

Ferroelectric (FE) materials are of high technological interest because of their extraordinary dielectric, electro-optic, pyro- and piezoelectric properties. Their fields of application range from actuators and sensors through to data and energy storage. Conventional ferroelectrics usually possess a so-called Perovskite structure and are comparably complex oxides as evidenced by lead zirconate titanate (PbZrxTi1-xO3, PZT) as one of the most important examples.Prior to the first funding period, the first observation of FE properties in 10 nm thin Si-doped HfO2 films was published by the applicants. This finding was especially surprising given the intense research devoted to HfO2 as ceramic material as well as for ultrathin high-permittivity dielectrics in semiconductor technology. The origin of this ferroelectricity remained unclear. An orthorhombic Pca21 phase was proposed to explain the behavior. The experimental proof could not be provided up to that point. Doping and mechanical stress were discussed to potentially account for the stabilization of the FE phase. Therefore, the experimental and theoretical investigations were aligned along the working hypothesis that pure HfO2 is an incipient ferroelectric which could overcome the inherently small barrier between the para- and the ferroelectric state promoted by the abovementioned levers. The report section contains a discussion of I) the stabilization and the experimental proof of the Pca21 phase; II) the suitability of different preparation methods with focus on the cost-efficient, flexible chemical solution deposition; III) the manifestation and aptitude of different dopants; IV) the previously only sparsely considered field cycling behavior of HfO2-based ferroelectrics.Goal of the extension proposal is to deepen the physical and theoretic understanding of the stabilization of the ferroelectric phase as well as of the mechanisms that account for the field cycling behavior in HfO2-based thinfilms. This is of outstanding relevance for both fundamental material science and future applications. Starting point for the proposed studies are the findings of the first funding period, which allowed a clear identification of relevant factors toward a physical multiscale model of the system HfO2/ZrO2. Particular aspects are intended to be critically discussed in comparison to the classic Perovskite ferroelectrics. Here, analogies will be helpful but also differences shall be emphasized. The work packages are arranged around the following subgoals: I) an understanding of the influence of surface energy; II) analysis of the phase transitions and the polarization reversal; III) study of dopants not utilized yet; IV) elucidation of the role of oxygen vacancies; V) working out the differences to classic perovskite ferroelectrics.

铁电（FE）材料由于其非凡的介电、电光、热、压电性能而引起了高度的技术兴趣。它们的应用领域从执行器和传感器到数据和能量存储。传统的铁电体通常具有所谓的钙钛矿结构，并且是相当复杂的氧化物，锆钛酸铅（PbZrxTi1-xO3， PZT）是最重要的例子之一。在第一个资助期之前，申请人发表了对10nm硅掺杂HfO2薄膜的FE性质的首次观察。考虑到HfO2作为陶瓷材料以及半导体技术中的超薄高介电常数介电介质的激烈研究，这一发现尤其令人惊讶。这种铁电性的起源仍然不清楚。提出了一个正交的Pca21相来解释这种行为。到那时为止，还不能提供实验证明。讨论了掺杂和机械应力对FE相稳定的潜在影响。因此，实验和理论研究都与工作假设一致，即纯HfO2是一种早期铁电态，可以克服上述杠杆所促进的准电态和铁电态之间固有的小屏障。报告部分包含以下讨论：(1)Pca21相的稳定化和实验证明；II)不同制备方法的适用性，重点是成本效益高、灵活的化学溶液沉积；（三）不同掺杂物的表现和性质；IV)以前只很少考虑hfo2基铁电体的场循环行为。扩展提案的目标是加深对铁电相稳定的物理和理论理解，以及解释hfo2基薄膜中场循环行为的机制。这对于基础材料科学和未来的应用都具有突出的相关性。拟议研究的起点是第一个资助期的研究结果，它允许明确确定HfO2/ZrO2系统的物理多尺度模型的相关因素。与经典的钙钛矿铁电体相比，特定的方面将被批判性地讨论。在这里，类比是有帮助的，但也要强调差异。工作包围绕以下子目标安排：1)理解表面能的影响；II)相变和极化反转分析；III)尚未利用的掺杂剂的研究；IV)阐明氧空位的作用；V)找出与经典钙钛矿铁电体的区别。