Electrically Coupling Multifunctional Oxides to Semiconductors through Bandgap Engineering

点击翻译按钮获取中文摘要

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.