Controlling the growth of graphene on diamond substrates

• Main Author: Cooil, Simon
• Other Authors: Evans, David ; Langstaff, David
• Published: Aberystwyth University 2014
• Subjects: 500
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600145

The Epitaxial nature of graphene growth on the diamond (111) surface has been investigated using real-­‐time photoelectron spectroscopy (REES), Photoemission electron microscopy (PEEM), Angle resolved photoelectron spectroscopy (ARPES), low energy electron microscopy (LEEM) and low energy electron diffraction (LEED). Graphene regions were seen to co-­‐exist on the reconstructed 2×1 diamond surface following a high temperature in vacuum anneal at ~1000 °C. The graphene regions showed a π-­‐band dispersion along Κ-­‐Μ-­‐Κ that matches well with other calculations and experimental results of quasi-­‐free-­‐standing graphene. In the presence of a thin transition metal layer, the temperature at which the diamond surface undergoes conversion from sp3 to sp2 carbon is lowered. Here ordered films of Fe allow for the graphitisation of the diamond surface at ~495 °C. The order of the Fe film allows for registry to be transferred between the diamond surface and resulting graphene formation on the surface. An important aspect of this work is, the application of real-­‐time monitoring of in-­‐situ processing. Here REES is applied as a technique, which allows for precise control of the amount of graphene grown. Whilst monitoring the growth with real-­‐time imaging techniques such as LEEM allowed for investigation of the true growth optimum parameters. It was found that growth of graphene at 500 °C results in the formation large >100 μm regions which are strongly interacting with the substrate, displaying an n-­‐type doping of ~2.6 eV at the K-­‐point. The growth of qasi-­‐free-­‐standing graphene began at 530 °C however the slow growth rate at this temperature resulted in the formation of small islands made up of many graphene layers and rotational domains. Growth at 560 °C allowed for lateral growth of free-­‐standing monolayer regions across the sample surface. The grown material showed good registry to the substrate and displayed no sign of grain boundaries in LEED. The same catalytic process has been applied to the surface of SiC 6H-­‐(0001) and monitored using REES. Further control of the amount of graphene formed can by gained by the controlling the catalyst film thickness. A ~0.75nm thick film of Fe is expected to grow precisely 1 monolayer of graphene, as a result of the formation of a complete FeSi layer which terminates the graphitisation process.