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Impact of chemical vapour deposition plasma inhomogeneity on the spatial variation of sp 2 carbon in boron doped diamond electrodes

Ayres, Zoë J., Newland, Jonathan C., Newton, Mark E., Mandal, Soumen, Williams, Oliver Aneurin and Macpherson, Julie V. 2017. Impact of chemical vapour deposition plasma inhomogeneity on the spatial variation of sp 2 carbon in boron doped diamond electrodes. Carbon 121 , pp. 434-442. 10.1016/j.carbon.2017.06.008

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Abstract

The impact of plasma inhomogeneity on the sp2 content of thin film (∼micron) boron doped diamond (BDD) electrodes, grown using microwave chemical vapour deposition (MW-CVD) under different methane (CH4) concentrations (1% and 5%), is investigated. The sp2surface content (critical for interpreting electrochemical data) is comparatively assessed using a variety of electrochemical measurements: capacitance; solvent window analysis and quinone surface coverage. For all growths, distinctive regions containing appreciably differing amounts of sp2 carbon are identified, across the wafer. For example, on the 1% CH4 wafer, some areas exhibit electrochemical signatures indicative of high quality, minimal sp2 content BDD, whereas others show regions comprising significant sp2 carbon. Note Raman microscopy was unable to identify these variations. On the 5% CH4 wafer, no region was found to contain minimal levels of sp2 carbon. Changes in sp2 content across the BDD films indicates spatial variations in parameters such as temperature, methane and atomic hydrogen concentrations during growth, in this case linked directly to the use of a commonly employed multi-moded (overmoded) chamber for MW-CVD BDD synthesis. Varying sp2 levels can have significant impact on the resulting electrochemical behaviour of the BDD.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Publisher: Elsevier
ISSN: 0008-6223
Funders: ERC
Date of First Compliant Deposit: 6 June 2017
Date of Acceptance: 2 June 2017
Last Modified: 04 Jun 2018 22:09
URI: http://orca.cf.ac.uk/id/eprint/101208

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