# Structure and Electrical Properties of Carbon-Rich Polymer Derived Silicon Carbonitride (SiCN)
## 3 Results and Discussion
### Room Temperature Electrical Conductivity and Charge Carrier Transport Mechanism  
The room temperature conductivity of the amorphous carbon-rich SiCN produced at pyrolysis temperature of 1100 \({}^{\circ}\)C (in an argon atmosphere) was determined to be 1.48 \(\times\) 10\({}^{-1}\) S/cm (see Table 3). This result is concurrent with the submission of Cordelair that amorphous Si\({}_{\text{x}}\)C\({}_{\text{y}}\)N\({}_{\text{z}}\) is a semiconductor with room temperature dc conductivity in the range of 10\({}^{-4}\) to 10\({}^{2}\) S/cm [14]. However, this value is found to be at least 3 orders of magnitude higher than previously reported electrical conductivity of amorphous SiCN PDC materials prepared under similar temperature conditions [13,70]. The higher electrical conductivity recorded could be traced to the higher free carbon content. Various models governing the dependence of electrical properties of SiCN on fabrication pyrolysis temperature have been proposed [71, 72, 73, 74, 75], but electrical conductivity (\(\sigma_{\text{dc}}\)) dependence on temperature of amorphous semiconductors can best be described by variable range hopping of charge carriers (i.e., single/multiple phonon-assisted jumps of charge carriers near the Fermi level) described by [PERSON] (Equation (5)) [74, 75] (\(k\) is Boltzmann constant, \(\Delta\)E is the activation energy which equals the energy gap between Fermi level and conducting bands). Also, it has been shown that at higher temperatures (e.g., T \(\geq\) 1400 \({}^{\circ}\)C for SiCN PDCs), Arrhenius equation (see Equation (6)) describes temperature dependence of the RT \(\sigma_{\text{dc}}\)[9, 14, 76]. \[\sigma_{dc}=\sigma_{o}\exp-\left(\frac{T_{o}}{T}\right)^{\frac{1}{4}} \tag{5}\]  
\[\sigma_{dc}=\sigma_{o}\exp-\left(\frac{\Delta E}{kT}\right) \tag{6}\] \begin{table}
\begin{tabular}{c c c c c c} \hline
**Pyrolysis** & \multicolumn{3}{c}{**Elemental Composition (wt. \%)**} & \multirow{2}{*}{**N/Si (at. \%)**} & \multirow{2}{*}{**C/Si (at. \%)**} & **Carbon** \\
**Temperature** & **Si** & **C** & **N** & **Content (at. \%)** \\ \hline
1100 \({}^{\circ}\)C & 39.87 & 48.32 & 9.95 & 0.50 & 2.83 & 64.17 \\
1400 \({}^{\circ}\)C & 41.91 & 52.87 & 4.44 & 0.21 & 2.95 & 70.32 \\
1600 \({}^{\circ}\)C & 43.61 & 53.37 & 2.43 & 0.11 & 2.86 & 71.60 \\ \hline \end{tabular}
\end{table} 
Table 2: The chemical composition of the C/SiCN nanocomposites after pyrolysis. Figure 4: SEM images and EDS spectra showing the morphologies and energy peaks corresponding to the various elements respectively, of the pelletized C/SiCN nanocomposites pyrolyzed and heat treated between 1100–1600 \({}^{\circ}\)C in an argon atmosphere: (**a.i**) SEM images of the samples pyrolyzed at 1100 \({}^{\circ}\)C; (**a.ii**) EDS spectrum of the sample pyrolyzed at 1100 \({}^{\circ}\)C; (**b.i**) SEM images of the samples heat treated at 1400 \({}^{\circ}\)C; (**b.ii**) EDS spectrum of the sample heat treated at 1400 \({}^{\circ}\)C; (**c.i**) SEM images of the samples heat treated at 1600 \({}^{\circ}\)C; (**c.ii**) EDS spectrum of the sample heat treated at 1600 \({}^{\circ}\)C.  
Consequently, the RT conductivity of the samples prepared at an annealing temperature of 1400 \({}^{\circ}\)C increased to 4.70 S/cm and 9.26 S/cm at to 1600 \({}^{\circ}\)C. The noticed surge in electrical conductivity of the C/SiCN materials is attributed to the percolation and ordering of the graphitic domains with increasing the annealing temperature. A demanding search of the literature shows that the highest electrical conductivity of SiCN monolith so far reported is \(\sim\)1.0 S/cm (at 1700 \({}^{\circ}\)C) [9], but the conductivity value recorded on the synthesized C/SiCN nanocomposite in this study heat-treated at 1600 \({}^{\circ}\)C is much higher (9.26 S/cm); revealing the extent to which the temperature-dependent electrical properties of PDCs may be tailored corresponding to increase in the quantity and ordering of the free carbon.