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Microwave permittivity of trace sp2 carbon impurities in sub-micron diamond powders

Cuenca, Jerome Alexander ORCID:, Thomas, Evan Lloyd Hunter, Mandal, Soumen ORCID:, Morgan, David John ORCID:, Lloret, Fernando, Araujo, Daniel, Williams, Oliver Aneurin ORCID: and Porch, Adrian ORCID: 2018. Microwave permittivity of trace sp2 carbon impurities in sub-micron diamond powders. ACS Omega 3 (2) , pp. 2183-2192. 10.1021/acsomega.7b02000

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Microwave dielectric loss tangent measurements are demonstrated as a method for quantifying trace sp2-hybridized carbon impurities in sub-micron diamond powders. Appropriate test samples are prepared by vacuum annealing at temperatures from 600 to 1200 °C to vary the sp2/sp3 carbon ratio through partial surface graphitization. Microwave permittivity measurements are compared with those obtained using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and electron energy loss spectroscopy (EELS). The average particle size remains constant (verified by scanning electron microscopy) to decouple any geometric dielectric effects from the microwave measurements. After annealing, a small increase in sp2 carbon was identified from the XPS C 1s and Auger spectra, the EELS σ* peak in the C 1s spectra, and the D and G bands in Raman spectroscopy, although a quantifiable diamond to G-band peak ratio was unobtainable. Surface hydrogenation was also evidenced in the Raman and XPS O 1s data. Microwave cavity perturbation measurements show that the dielectric loss tangent increases with increasing sp2 bonding, with the most pertinent finding being that these values correlate with other measurements and that trace concentrations of sp2 carbon as small as 5% can be detected.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Cardiff Catalysis Institute (CCI)
Subjects: Q Science > Q Science (General)
Publisher: American Chemical Society
ISSN: 2470-1343
Date of First Compliant Deposit: 21 March 2018
Date of Acceptance: 26 January 2018
Last Modified: 27 Nov 2022 16:05

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