Development of long-range conductivity mechanisms in glass-like carbon

• Published in: Carbon (New York) 2024-04, Vol.223, p.119027, Article 119027
• Main Authors: Stritt, Jaspa, Cuenca, Jerome A., Thomas, Evan L.H., Williams, Oliver A.
• Format: Article
• Language: English
• Subjects: conductivity; Dielectric spectroscopy; Glass-like carbon; Microwave
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2024.119027

The conductivity mechanisms in glass-like carbon synthesised from SU-8 3005 photoresist are explored as a function of pyrolysis temperature (between 700–750 °C) utilising microwave dielectric spectroscopy techniques. Broadband measurements using an open-ended coaxial probe (BCP) are used to investigate the complex permittivity and conductivity as a function of frequency and show the development of long range conduction and sp2 carbon chain formation. Fixed frequency resonance measurements using microwave cavity perturbation (MCP) methods are shown as a way of measuring this transition and change in Q-factor without requiring contacts and therefore acting as a effective method for non-destructive and non-invasive measurements. Using these methods we show a clear change in the AC conductivity of glass-like carbon at a pyrolysis temperature of ∼730 °C and demonstrate how microwave cavity perturbation (MCP) can be used as a non-contact method of dielectric spectroscopy for determining the transition of conductivity mechanisms in glass-like carbon from short to long range and therefore as a method for non-destructive material quality control. We demonstrate that both BCP and MCP dielectric spectroscopy methods are effective at clearly detecting changes in the structure and conductivity mechanisms of glass-like carbon over a small pyrolysis temperature range. [Display omitted]