adatom decorated graphene for spintronic applications

Lead Research Organisation: University of York
Department Name: Physics

Abstract

Adatom-decorated graphene is an exciting new subfield in the broader arena of 2D materials that specifically seeks to make breakthroughs in the area of graphene spintronics. Spin-based transistors are one of the most eagerly pursued goals of spintronics research yet their realisation awaits emergent nanomaterials with suitable properties. Graphene is one of the most promising candidates however it is clear that for the next stage of device development, a much deeper understanding of the interplay between fundamental material properties and device performance is required. The aim of this project is to provide this understanding by investigating how the electronic, chemical, and magnetic properties of graphene can be tailored through the addition of extra atoms (adatoms) such as fluorine at specific locations. Achieving this goal will rely on a strong overlap of theory and experiment and this will be at the heart of the PhD project. The student will initially investigate various methods of graphene fabrication including mechanical exfoliation and chemical-vapour deposition. A variety of advanced materials characterisation techniques will be used to probe the properties of graphene and relate these to those predicted by theoretical calculations based on the latest effective tight-binding models. Experimental techniques will focus on scanning tunnelling microscopy and spectroscopy and electron spectroscopy including the use of a spin-polarised beam of metastable helium atoms, an approach unique to York. Chemical modification of the graphene will then be investigated by doping the material with various adatoms such as fluorine, which has been shown to inducespin-orbit coupling presenting a viable pathway to spintronic applications.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509802/1 01/10/2016 31/03/2022
1796996 Studentship EP/N509802/1 01/10/2016 30/09/2019 Phillip Bentley
 
Description In my thesis we present the first results from using a spin polarised metastable emission electron microscope (SPMEEM). This unique technique involves using spin-polarised helium atoms prepared in the 23S metastable state to probe the top-most spin-split surface density of states and therefore determine the magnetic properties at the interface of various materials. This was used to successfully image domains at the top-most surface of magnetite(001) in addition revealing interesting phenomena regarding this particular magnetic material. The importance of these results is that they further demonstrate how the magnetic properties of the top-most atoms differ from those in bulk. In order to design devices for spintronic (spin electronic) applications, determining these properties at the interface is crucial and therefore SPMEEM presents itself as a powerful tool to characterise such properties. This will lead to several publications which are currently in preparation.

My thesis also presented further data on how graphene grown on SiC can be tailored for electronic and spintronic applications. Graphene and many other 2D materials, present a wide variety of beneficial electrical, mechanical, and optical properties which make them attractive for a wide variety of applications. Yet crucial to their use, it is first important to understand how these materials behave when coupled with other materials as well as how they can be produced. I therefore explored graphene on SiC to help shed further light on this material, leading to one publication which is in press and another which is currently in preparation. The importance of this work is it sheds further light on how graphene/SiC can be tuned for spintronic applications as well as what challenges are faced when developing such devices.

Finally, in my thesis we explored organic molecules on substrates of LSMO. Like 2D materials, such organic molecules / magnetic substrates, named as spinterfaces, present a variety of unique electronic and magnetic properties which make them attractive for a variety of applications. Yet, like 2D materials, understanding these spinterfaces is crucial before they are used in devices. So using the surface sensitivity of this metastable helium technique, we were able to shed further light on one of these spinterfaces for which a paper is currently under review.
Exploitation Route 2D materials are of interest not only with spintronics, but photonics and even biological applications. SiC, like Si, is an attractive semiconductor with a wide variety of applications. Iron oxides such as Fe3O4 (magnetite) are of interest within not only spintronics, but also biomedical applications such magnetic hyperthermia for treating cancer. Finally, organic spinterfaces are not only applicable within spintronics but may also have uses within photonics as well. Therefore, it is critical to determine the surface properties of all the materials listed above and to achieve this incredibly surface sensitive techniques are required. SPMEEM and its associated spectroscopic technique spin-polarised metastable de-excitation spectroscopy (SPMDS) present themselves as techniques to characterise such surface properties. Therefore the results presented in my thesis in addition to publications which are either in preparation or are in press, demonstrate the benefits afforded by SPMEEM and SPMDS and may help lay the groundwork for others to use to develop devices or such which incorporate such materials, whether for electronic or biomedical applications for example.
Sectors Aerospace, Defence and Marine,Electronics,Energy,Pharmaceuticals and Medical Biotechnology