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

The conductivity mechanisms in glass -like carbon synthesised from SU-8 3005 photoresist are explored as a function of pyrolysis temperature (between 700-750 degrees 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 sp 2 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 similar to 730 degrees 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.