Chemical Routes to the Growth of Crystalline Functional Oxides on Germanium

半导体行业在不到10纳米的时代面临着新的挑战，因为规模将不再主导电子设备的性能改进。新材料和材料组合提供了改善性能和功能的机会，而对设备结构的改变最小。例如，使用锗作为衬底可以提供更低的功耗和更快的计算速度。而使用既具有磁性又具有电子性质的钙钛矿氧化物作为功能层，可以实现先进的存储器件、集成的光隔离器和自旋电子器件。这项研究将探索如何在锗上直接生长这些结晶的钙钛矿氧化物薄膜。这项研究探索了一种全化学增长过程，这种过程应该是可扩展的，从拥有成本的制造成本来看，内在成本较低，并且基于现有的制造设备。其影响将体现在使未来的设备能够利用电荷和自转的过程中。此外，这位研究人员还参与了一个名为“爱丽丝梦游仙境”的推广项目，旨在吸引女高中生学习物理科学和工程学。这些来自当地高中的学生将在德克萨斯大学奥斯汀分校度过暑假，在一个支持性的环境中参与研究。这项研究的主要目标是了解和描述在可扩展和可制造的化学沉积过程中，导致在Ge(001)上形成具有所需铁电和铁磁性质的晶态多铁氧化物的过程。这项研究探索了铁掺杂的钛酸钡，铁含量高达20%，以及直接在Ge上生长的铋铁氧体晶体氧化物。这项研究使用分子束外延来制备定义良好的表面，原子层沉积来生长外延结构；使用原位电子和光子光谱来表征薄膜和界面；非原位透射电子显微镜，以及X射线散射、磁性和电学测量建立了结构-性质关系。这项研究得益于首席研究员带来的基础设施、相关研究和专业知识的邻接关系，以及原子控制生长、材料表征、表面化学和电学性质测量。基础研究的具体重点领域包括：1)阐明导致结晶氧化物形成的Ge(001)氧化物界面上的反应和结构变化；2)了解导致结晶薄膜的钙钛矿层中结构的演变，以及结构如何依赖于工艺条件；以及3)在具有铁电和铁磁/反铁磁性质的多铁性氧化物的背景下建立结构-性质-功能关系。

The semiconductor industry faces new challenges in the sub-10 nanometer era as scaling will no longer dominate performance improvement for electronic devices. New materials and combinations of materials provide an opportunity to improve performance and function with minimal change to the device construction. For example, using germanium as the substrate can provide both lower power consumption and faster computing speeds. And using perovskite oxides that are both magnetic and electronic as the functional layer can enable advanced memory devices, integrated optical isolators and spintronic devices. The research will explore how to grow these crystalline perovskite oxide films directly on germanium. The research explores an all-chemical growth process that should be scalable, is inherently less costly from a manufacturing cost of ownership, and is based on current manufacturing equipment. The impact will be in processes to enable future devices that exploit charge and spin. As well, the researcher engages in an outreach program called "Alice in Wonderland" that is aimed at attracting female high-school students to the physical sciences and engineering. These students from local high schools will spend their summers at the University of Texas at Austin participating in research within a supportive environment. The overarching objectives of this research are to understand and describe processes that lead to the formation of crystalline multiferroic oxides on Ge(001) with the requisite ferroelectric and ferromagnetic properties in a chemical deposition process that is scalable and manufacturable. The research explores iron-doped barium titantate, with iron levels up to 20 percent, and bismuth ferrite crystalline oxides grown directly on Ge. The research uses molecular beam epitaxy to prepare well-defined surfaces and atomic layer deposition to grow the epitaxial structures; in situ electron and photon spectroscopies are used to characterize the films and interfaces; and ex situ transmission electron microscopy, and x-ray scattering, magnetic and electrical measurements establish structure-property relations. The research benefits from the infrastructure, adjacency of related research and expertise the principal investigator brings in atomically controlled growth, materials characterization, surface chemistry, and electrical property measurement. Specific focus areas for the fundamental studies include: 1) elucidating the reactions and structural changes at the Ge(001) oxide interface that seed crystalline oxide formation; 2) understanding the evolution of structure in the perovskite layer leading to a crystalline film and how the structure depends on process conditions; and 3) establishing the structure-property-function relationships in the context of a multiferroic oxide that features ferroelectric and ferro-/antiferromagnetic properties within a temperature window that is technologically relevant.