Synchrotron radiation characterisation of surface and interface properties of two-dimensional material platforms

Program Code: 
1892
Contact: 

A/Prof Heiko Timmers (h.timmers@adfa.edu.au)

Description of Work: 

Objectives:

The potential of carbon-based graphene materials has been demonstrated and is one of the most important research areas in contemporary materials physics and engineering [1-3]. Other two-dimensional materials, such as black phosphorus and hexagonal boron-nitride, are presently also being developed and present a completely new type of materials physics.

 

Two-dimensional materials consist of only a one-atom thick plane of atoms. As a consequence, graphene is effectively a metal with a zero band-gap, whereas black phosphorus may be considered a semiconductor. The energy-momentum relation in graphene is linear for low energies leading to zero effective mass for electrons and holes and thus resulting in extremely fast charge carrier transport [2,3]. Originally made using just sticky tape and pencil lead, graphene and black phosphorous do not readily fit the conventional expectations for electronic materials. Furthermore their mechanical stability, combined with considerable elasticity and atomic scale thinness, make them effectively a new material class that promises to revolutionize technology [3].

 

Graphene is believed to be an ideal material for spintronics, which would be a dramatic improvement on current electronics technology. Recent theoretical studies suggest the use of graphene also as a building block in spin-filtering devices. As the spin-dependent transport is affected by interface and surface quality, the graphene-nickel system is for example of special interest, providing an ideal interface from a structural point of view. However, any unwanted surface ad-sorbates can interfere, while intercalation of foreign elements at the interface may affect the structural integrity.

 

Prior to to implementing graphene and other two-dimensional systems in any kind of spintronic device, studies of the electronic interfacial and surface properties of the materials have to be performed. Such studies are the focus of this project. Only when the surface physics of two-dimensional materials has been understood in detail, can the technological implementation of this exciting new material class be contemplated. The work proposed here has the potential to make significant contribution to this expected advance. Results on two-dimensional materials are currently very topical, so that publication in high-profile journals such as Nature and Physics Review Letters may be possible.

 

Description of Work:

This PhD-project will employ the sensitive XPS-technique using synchrotron radiation, which can detect bonding configurations that are present at the material surface and at the interface with the substrate. Additional information will be obtained from NEXAFS- and XRD-characterisation, which are both sensitive to structural properties of the materials.

The project will take advantage of existing instruments at the Australian Synchrotron to perform such experiments, as well as employing UNSW Canberra equipment. The work will be performed as a member of the Condensed Matter and Materials Group and the research team of Associate Professor Heiko Timmers. Future processing of two-dimensional materials and, in particular, the controlled modification of their surface via ion implantation will also be attempted. Such materials modifications will be characterized with SEM and AFM at UNSW Canberra. The combination in this project of a number of high-tech characterization techniques and the associated complex physics requires an outstanding PhD-student.

 

References:

 [1] A. K. Geim and K. S. Novoselov,  The rise of graphene, Nature Mat., 6, 183 (2007).

[2] A. K. Geim, Graphene: Status and Prospects, Science, 324, 1530 (2009).

[3] A.H.C. Neto et al., The electronic properties of graphene, Rev. Mod. Phys. 81 (2009).