Ferroelectric zirconium oxide for piezo- and pyroelectric devices (Zeppelin)

基于氧化铪（HfO 2）的新型铁电材料体系是2007年发现的，具有高介电极化、低介电常数、无铅和硅兼容等特点。然而，到目前为止，这些有利的特性主要仅在约10 nm的HfO 2薄层中实现。2018年完成的DFG项目INFEROX研究了各种掺杂剂和铌-氧化锆的掺杂HfO 2薄膜的生产，表征了材料特性，并使用密度泛函理论计算了自由能，以了解模拟与实验观察之间的关系。总的来说，该项目旨在研究新型电子设备材料的基础。这些材料的压电和热释电性能已被发现是有前途的，但没有系统的研究。该建议建议将HfO 2基层的研究扩展到ZrO 2基掺杂层，并产生约1 μm的较厚层。CSD，ALD和PVD，无论是从陶瓷和金属靶，被选为沉积方法来研究缺陷的影响。重点是可控的介电，压电和热电性能，这可以是巨大的场驱动相变，并导致特别高的性能数字。该项目调查了介电，压电和热电性能的起源，优化了性能，并确定了传感器和致动器设备，如变容二极管，薄膜声谐振器（TFBAR）和IR传感器的性能数据。为了实现这些器件，需要1 µm量级的厚层。特别地，铁电相将在这些厚层中稳定或通过场驱动或温度驱动过程来支撑。根据先前的理解，该相受到界面能、氧空位的影响，但也部分受到亚稳相的影响。此外，研究的一个重要目标是更好地理解和控制相形成和稳定的动力学。在理论方面，计划进行掺杂剂调查，相变动力学分析，以及与实验结果相比的压电和热释电性能的计算。

The new ferroelectric material system based on hafnium oxide (HfO2) was discovered in 2007 which is characterized by high remanent polarization and low dielectric constant, and is also lead-free and silicon compatible. However, so far these advantageous properties have mostly been realized only in thin layers of HfO2 around 10 nm. The 2018 completed DFG project INFEROX investigated the production of thin, doped HfO2 films for a variety of dopants and for hafnium-zirconia, characterized the material properties, and calculated the free energies with density functional theory to understand the relationship between simulations and experimental observations. Overall, the project was aimed at researching the fundamentals of materials for novel electronic devices. The piezoelectric and pyroelectric properties of these materials have been found to be promising, but were not systematically studied. This proposal suggests to extend the investigation of HfO2-based layers to ZrO2-based doped layers and to produce thicker layers on the order of 1 μm. CSD, ALD and PVD, both from ceramic and metallic targets, are chosen as the deposition method to study the impact of defects. The focus is on the controllable dielectric, piezoelectric and pyroelectric properties, which can be giant in field-driven phase transitions and lead to particularly high performance figures. The project investigates the origins of the dielectric, piezoelectric and pyroelectric properties, optimizes the properties and determines the performance figures of sensor and actuator devices such as varactors, thin-film acoustic resonators (TFBARs), and IR sensors. For the realization of these devices, thick layers on the order of 1 µm are required. In particular, the ferroelectric phase is to be stabilized in these thick layers or supported by field-driven or temperature-driven processes. According to previous understanding, this phase is impacted by interfacial energy, oxygen vacancies, but in part also by metastable phases. In addition, an important goal of the investigation is to better understand and control the kinetics of phase formation and stabilization. On the theoretical side, it is planned to perform a dopant survey, an analysis of the kinetics of the phase transitions, as well as the calculation of piezo and pyroelectric properties in comparison with experimental results.