Electrically Coupling Multifunctional Oxides to Semiconductors through Bandgap Engineering

非技术描述：通常需要新材料来进一步推进用于计算机和清洁能源采集的技术。该项目寻求将半导体和氧化物这两种不同类别的材料结合起来，作为创造具有新性能的新复合材料的一种手段。该项目通过将薄膜逐层堆叠在一起并在原子水平上进行精确控制来制备这些新材料，并探索了堆叠材料系统产生的新的物理性质。除了科学和技术的影响，这项研究还为研究生和本科生提供了材料生长和表征方面的前沿培训，为他们在STEM相关领域的职业生涯做好准备。此外，教育和推广活动在传播研究成果时将艺术和科学结合起来，旨在鼓励高中生从事STEM领域的研究。技术描述：开发新型功能材料的基本方法是在层状、异质结构中将具有互补特性的材料进行结构和电子耦合。这个项目的重点是了解共价半导体如何与离子复合氧化物结合，以创造超出任何组成材料本身的功能。氧化物与半导体的电偶联和实现新功能的关键是控制异质界面的能带排列。这个项目试图阐明三种形式的电耦合，即电荷输运，电荷隧道和极化耦合的能带排列。这样的理解可以使氧化物的铁磁、铁电和介电特性与半导体相结合，用于一系列应用。特别是，该项目专注于利用最先进的氧化物分子束外延技术在GaAs和Ge上直接生长单晶锆酸盐SrZrO_3和固溶体SrZrTiO_3。能带偏移量通过化学计量比、应变和界面结构来控制。用X射线光电子能谱、X射线衍射仪和扫描电子显微镜对锆酸盐-半导体异质结的电子结构和物理结构进行了表征。通过电流-电压和电容-电压测量研究异质结的电学行为，以确定输运、隧穿和极化特性。

Non-Technical Description: New materials are often required to further advance technologies used for computers and clean energy harvesting. This project seeks to combine two different classes of materials, namely, semiconductors and oxides, as a means to create new composite materials with novel properties. This project fabricates these new materials by stacking thin films together in a layer-by-layer fashion with precise control at the atomic level and explores the new physical properties resulting from the stacked materials systems. In addition to scientific and technological impacts, this research also provides training to graduate and undergraduate students in the forefront of materials growth and characterization to prepare them for careers in STEM related fields. Furthermore, the education and outreach activities combine art and science in disseminating the research findings, aiming at encouraging high-school students to pursue STEM fields of study.Technical Description: A fundamental approach of developing novel functional materials is to structurally and electrically couple materials exhibiting complementary properties within layered, heterogeneous structures. This project focuses on understanding how covalent semiconductors can be coupled with ionic complex oxides to create functionalities beyond any of the constituent materials alone. Key to electrically coupling oxides to semiconductors and realizing novel functionalities is to control the band alignment at the heterogeneous interfaces. This project seeks to elucidate the band alignments in three forms of electrical coupling, namely, charge transport, charge tunneling and polarization coupling. Such understanding could enable the ferromagnetic, ferroelectric and dielectric properties of oxides to be coupled with semiconductors for a range of applications. Particularly, the project focuses on the growth of single-crystalline zirconates SrZrO3 and solid-solution SrZrTiO3 directly on GaAs and Ge using state-of-the-art oxide molecular beam epitaxy. Band offset is controlled via stoichiometry, strain and interfacial structure. The electronic and physical structure of the zirconate - semiconductor heterostructures is characterized using X-ray photoemission, X-ray diffraction and scanning transmission electron microscopy. Electrical behavior of the heterojunctions is investigated via current-voltage and capacitance-voltage measurements in order to determine transport, tunneling, and polarization characteristics.