Liquid-metal Assisted Confinement Heteroepitaxy of Magnetic Elements and Alloys
Abstract
Quantum confinement of metals may enable unique electronic, photonic, and magnetic properties such as topological behavior, superconductivity, non-linear optical response, and ferromagnetism - the key ingredients for next-generation quantum technologies. However, crystalline quantum confined (QC) metals are largely unexplored due to their rapid oxidation when removed from the growth chamber, thus only a few examples of nanometer-thick crystalline metals have been experimentally demonstrated, typically under ultrahigh vacuum conditions. Therefore identifying and understanding how to create environmentally stable, single-crystal QC allotropes of 3D magnets will enable a transformative new material platform with lasting impact on science, technology, and society. Our key advance towards this end is Confinement Heteroepitaxy (CHet), a new growth method that imposes a unique set of upper and lower surface boundary conditions on the QC metal. In CHet, epitaxial graphene first forms by silicon sublimation from silicon carbide (SiC), followed by the controlled introduction to defects in the graphene. Various elements are then intercalated and reacted within the confines of a graphene/SiC interface: the high-energy SiC interface then templates the QC crystalline form of the intercalant while the graphene overlayer provides robust environmental protection. The proposed work aims to expand CHet to create QC magnetic metals (Fe, Co, Mn) and understand how utilization of unique liquid-metal alloy precursors, graphene defect structure and chemistry, and the graphene/intercalant/SiC interface chemistry control intercalation into, diffusion along, and layering within the graphene/SiC interfacial gallery, thereby controlling the final physicochemical properties of QC refractory metals grown via CHet. These phenomena are generic and generalizable and thus CHet promises to be a fundamental and far-reaching advance in the synthesis science of quantum confined systems. We will employ a closed loop of synthesis and characterization to (1) investigate intercalation of Fe, Co, and Mn via utilization of a liquid-metal alloy precursors by combining the magnetic elements with Ga to dramatically reduce their melting temperature for the CHet process; (2) investigate how co-intercalation is affected by intercalant choice and ratio, graphene properties, and the graphene/SiC interface; (3) elucidate how Ògraphene healingÓ impacts the intercalation of the alloy; and (3) evaluate how confinement of magnetic alloys impacts their properties. Through collaboration, we will utilize theoretical calculations will map out thermodynamic stability (including the key role played by interfacial energetics), quantify electronic properties, evaluate key kinetic barriers, and explore the structure-property relationships of 2D-Ms, thus helping to guide and interpret experimental efforts. Experiments will utilize CHet to create, investigate, and engineer the characteristics of these new forms of 2D-Ms. This proposal is unique in the rapidly expanding research enterprise that is quantum confinement effect on magnetic materials. It will establish a synthesis technique capable of routinely realizing atomically thin forms of non-van der Waals structures that can be readily incorporated into new quantum devices. The newly developed approach will define a new synthetic materials platform of QC systems not otherwise attainable. This specific combination promises to develop graphene intercalation as a robust new pathway for the synthesis of QC metals and alloys and establish the governing synthetic principles of this platform, including the roles of reaction kinetics and interfacial energetics as they guide precursor choice and reaction conditions. The work will advance understanding and control of the behavior of 3D materials in their quantum limit.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 02, 2020
- Source ID
- W911NF2110037
Entities
People
- Joshua A. Robinson
Organizations
- Army Contracting Command
- Pennsylvania State University
- United States Army