Alkali metal containing materials have become increasingly attractive in a world hunting for sustainable energy materials and green functional devices. Lithium- and sodium battery technology, lead-free piezo- and ferroelectric devices, and record-breaking alkali doped tandem perovskite solar cells are among the applications where alkali metal-containing thin films get increasing attention. Atomic layer deposition (ALD) is one of the enabling thin film deposition techniques that offer chemical and geometrical versatility to realize the implementation of such thin films on an applicable scale. The drawback has until recently been a lack of available precursor chemistry that offers self-limiting growth that is fundamental to ALD. The alkali metal tert-butoxides have been shown to exhibit the necessary properties to facilitate saturating growth for Li-, Na-, K-, and Rb-containing compounds. However, the behavior of the tert-butoxides in ALD-growth has been considered difficult to unravel, with processes exhibiting limited control and low reproducibility. Very little has been reported on trends in reaction mechanisms as the mass of the alkali metal increases. Herein, we summarize the existing literature on the use of alkali metal tert-butoxides as precursors in ALD. We consider differences in the structure and behavior of the tert-butoxides as the alkali metal cation becomes heavier. In addition, we present precursor synthesis routes and key information on precursor structure, stability, and mechanistic behavior. Finally, we provide the first ever report of Cs-containing films by ALD to complement previous work on its lighter counterparts.

中文翻译：

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叔丁氧化物作为含碱金属薄膜原子层沉积的前体

在世界范围内寻找可持续能源材料和绿色功能设备的过程中，含碱金属材料变得越来越有吸引力。锂和钠电池技术，无铅压电和铁电设备以及创纪录的碱掺杂串联钙钛矿型太阳能电池是含碱金属薄膜日益受到关注的应用。原子层沉积（ALD）是一种使能的薄膜沉积技术，可提供化学和几何多功能性，以实现可应用规模的此类薄膜。直到最近，该缺点一直是缺乏可利用的前驱物化学物质，该化学物质提供自限性生长，这是ALD的基础。碱金属叔-已证明丁醇盐显示出必要的特性，以促进饱和的含Li，Na，K和Rb化合物的生长。然而，认为叔丁醇盐在ALD生长中的行为难以解开，其工艺显示出有限的控制性和低可重复性。随着碱金属质量的增加，关于反应机理趋势的报道很少。在这里，我们总结了有关使用碱金属叔丁醇盐作为ALD前体的现有文献。我们认为，在结构和行为的差异叔-丁氧化物作为碱金属阳离子变得更重。此外，我们介绍了前驱体合成路线和有关前驱体结构，稳定性和机械行为的关键信息。最后，我们提供了ALD首次发布的含Cs薄膜的报告，以补充其较轻的同类产品的先前工作。