Moscow Institute of Physics and Technology , Institutskii per. 9, 141700 Dolgoprudny, Moscow Region, Russia.
NaMLab gGmbH/TU Dresden , Noethnitzer Strasse 64, 01187 Dresden, Germany.
ACS Appl Mater Interfaces. 2018 Jan 24;10(3):2701-2708. doi: 10.1021/acsami.7b15110. Epub 2018 Jan 9.
HfZrO thin films are one of the most appealing HfO-based ferroelectric thin films, which have been researched extensively for their applications in ferroelectric memory devices. In this work, a 1 mol % La-doped HfZrO thin film was grown by plasma-assisted atomic layer deposition and annealed at temperatures of 450 and 500 °C to crystallize the film into the desired orthorhombic phase. Despite the use of a lower temperature than that used in previous reports, the film showed highly promising ferroelectric properties-a remnant polarization of ∼30 μC/cm and switching cycle endurance up to 4 × 10. The performance was much better than that of undoped HfZrO thin films, demonstrating the positive influence of La doping. Such improvements were mainly attributed to the decreased coercive field (by ∼30% compared to the undoped film), which allowed for the use of a lower applied field to drive the cycling tests while maintaining a high polarization value. La doping also decreased the leakage current by ∼3 orders of magnitude compared to the undoped film, which also contributed to the strongly improved endurance. Nonetheless, the La-doped film required a larger number of wake-up cycles (∼10 cycles) to reach a saturated remnant polarization value. This behavior might be explained by the increased generation of oxygen vacancies and slower migration of these vacancies from the interface to the bulk region. However, the maximum number of wake-up cycles was less than 0.01% of the total possible cycles, and therefore, initializing the film to the maximum performance state would not be a serious burden.
铪锆氧化物（HfZrO）薄膜是最具吸引力的基于氧化铪的铁电薄膜之一，因其在铁电存储器器件中的应用而得到广泛研究。在这项工作中，通过等离子体辅助原子层沉积（PALD）生长了 1 摩尔%镧掺杂的 HfZrO 薄膜，并在 450 和 500°C 的温度下退火，以使薄膜结晶为所需的正交相。尽管使用的温度低于以前报道的温度，但该薄膜表现出了非常有前景的铁电性能-剩余极化约为 30 μC/cm，开关循环耐久性高达 4×10。性能明显优于未掺杂的 HfZrO 薄膜，证明了镧掺杂的积极影响。这种改进主要归因于矫顽场的降低（与未掺杂的薄膜相比降低了约 30%），这使得可以使用较低的外加场来驱动循环测试，同时保持较高的极化值。与未掺杂的薄膜相比，镧掺杂还将漏电流降低了约 3 个数量级，这也有助于显著提高耐久性。尽管如此，掺杂后的薄膜需要更多的唤醒循环（约 10 个循环）才能达到饱和的剩余极化值。这种行为可能是由氧空位的增加以及这些空位从界面向体区的迁移速度较慢引起的。然而，唤醒循环的最大次数不到总可能循环次数的 0.01%，因此，将薄膜初始化到最大性能状态不会造成严重负担。
