# 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 electrical properties of the C/SiCN nanocomposites investigated using Hall measurement showed an anomalous shift in the majority charge carriers from n-type in the glassy matrix pyrolyzed at 1100 \({}^{\circ}\)C to p-type in the ceramic samples prepared at T \(\geq\) 1400 \({}^{\circ}\)C (see Figure 5a-c). Recall that evaluation of the crystallization of the carbon-rich SiCN samples supported using XRD indicates that the material is amorphous at 1100 \({}^{\circ}\)C and crystalline at T \(\geq\) 1400 \({}^{\circ}\)C (Figure 3). Besides, phase composition of the amorphous SiC(N) is comparable to that of SiC doped with nitrogen [9]. Nitrogen dopant is commonly used for producing n-type SiC semiconductors [77, 78]. In the amorphous state, therefore, the transport mechanism of the carbon-rich SiCN samples appears to behave similar to that of SiC doped with nitrogen by showing predominant n-type charge carriers. Moreover, the presence of nitrogen doped SiC in SiCN PDCs pyrolyzed in nitrogen atmosphere has been recently reported, corroborated with results obtained using TEM, XANES-spectroscopy, XRD and Raman-spectroscopy [9]. In addition, it is known that sp\({}^{3}\) carbon is a good electron insulator while sp\({}^{2}\) carbon is an excellent charge transmitter [79], and as shown earlier in Figure 1a (by the prominence of the D\({}^{\prime}\) and T Raman bands), the pre-eminence of the insulating sp\({}^{3}\) carbon can be seen in the amorphous C/SiCN sample at 1100 \({}^{\circ}\)C. This may have led to the low carrier mobility and conductivity recorded at the 1100 \({}^{\circ}\)C temperature (see Table 3). On the other hand, the crystalline carbon-rich SiCN semiconductors produced at pyrolysis temperatures of 1400 \({}^{\circ}\)C and 1600 \({}^{\circ}\)C show a change in the predominant charge carrier to p-type. The nature of graphitic carbon charge carriers has been previously described as a reproducible positive Hall coefficient signal of hole-dominated transport (p-type) [80], and the p-type carriers shown by the C/SiCN PDCs could be linked to the prevailing ordering and percolation network of the graphitic phase within the nanocomposites at the higher temperatures. The progressive ordering, amount and size of the sp\({}^{2}\) carbon at 1400 \({}^{\circ}\)C and 1600 \({}^{\circ}\)C can be confirmed by the consistent increase in the lateral crystallite size (L\({}_{\rm a}\)), as well as the average continuous graphene length including tortuosity (L\({}_{\rm eq}\)) as the pyrolysis temperature increases. Furthermore, between 1100 \({}^{\circ}\)C and 1400 \({}^{\circ}\)C \(\leq\) T \(\leq\) 1600 \({}^{\circ}\)C, the sp\({}^{3}\) to sp\({}^{2}\) conversion is revealed via puniness of the D\({}^{\prime}\) and T Raman bands (see Figure 1b,c), leading to corresponding increases in the carrier mobility and electrical conductivity (Table 3), as well as the percolation network of the free carbon within the nanocomposites to display the recorded shift from the n-type to a p-type semiconductor. \begin{table}
\begin{tabular}{c c c c} \hline
**Parameter/Temperature** & **1100 \({}^{\circ}\)C** & **1400 \({}^{\circ}\)C** & **1600 \({}^{\circ}\)C** \\ \hline Electrical conductivity \(\sigma_{\rm dc}\), (S/cm) & 0.148 & 4.71 & 9.26 \\ Carrier density, \(N\) (cm\({}^{-3}\)) & 6.42 \(\times\) 10\({}^{18}\) & 8.45 \(\times\) 10\({}^{19}\) & 1.63 \(\times\) 10\({}^{19}\) \\ Carrier mobility, \(\mu_{\rm H_{\rm{\rm{H}}}}\), (cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\)) & 1.45 \(\times\) 10\({}^{-1}\) & 3.52 \(\times\) 10\({}^{-1}\) & 3.55 \\ \hline \end{tabular}
\end{table} 
Table 3: Electrical properties of the carbon-rich SiCN materials.