Spin Functional Materials with Atomic Layer Precision

The project focuses on using molecular beam epitaxy (MBE) to grow novel spin-functional materials with high precision, down to single atomic layers. The long-term impact of such fundamental materials physics research likely lies in information technologies such as solid-state quantum computation systems and low-power memory and information processing devices. Companies such as Toshiba Research Europe Ltd. (Cambridge) have an interest in these classes of materials and have previously worked with the Warwick group. The project uses an existing MBE system, previously funded under EPSRC projects EP/K03278X/1 and EP/K032852/1, "Half-metallic ferromagnets: materials fundamentals for next-generation spintronics". This system is capable of in situ structural characterisation via reflection high energy electron diffraction (RHEED) and scanning tunnelling microscopy (STM). However, we are also building a new MBE system both to broaden the range of accessible materials and to enhance the in situ analytical capability. The new machine will be capable of growing selected topological insulator and 2D (layered) materials, and will have a suite of electron spectroscopy capabilities (X-ray, UV and Auger electron spectroscopy as well an inverse photoemission) plus low energy electron diffraction (LEED) and RHEED. Further electronic structure characterisation will be performed by angle-resolved photoemission (ARPES) both in Warwick and at Diamond Light Source, initially using a vacuum suitcase to maintain pristine surfaces but subsequently attaching the Warwick ARPES analysis chamber directly to the MBE. Few MBE systems have this range of in situ characterisation capability, allowing us to both rapidly improve growth recipes for novel thin film spintronic materials and measure their electronic band structure. The system will also have a chamber for metal contact deposition, allowing complementary ex situ characterisation by magneto-transport, and an in situ four-point probe for basic electrical transport measurements. The research is relevant to EPSRC research areas including Condensed matter: magnetism and magnetic materials since we will be growing half-metallic ferromagnetic layers and 2D materials with perpendicular magnetic anisotropy. The in situ ARPES development will benefit EPSRC's efforts in Condensed matter: electronic structure. The spin-functional materials have potential applications in the EPSRC areas of Quantum devices, components and systems and Spintronics. The development of multiple complementary surface-sensitive techniques alongside MBE growth, all in ultra-high vacuum, is highly relevant to EPSRC's portfolio in Surface Science. The overall objectives are to (1) exploit the existing MBE system in refining our understanding of half-metallic ferromagnetic layers incorporated into semiconductor structures, focusing on Sb-based systems, (2) build a new MBE-photoemission system with flexible materials growth capability and strong in situ analysis, (3) exploit the new MBE system to grow and analyse prstine2D and topological materials down to single atomic layer thickness.