# A SiCN Thin Film Thermistor Based on DVB Modified Polymer-Derived Ceramics
## 3 Results
### Electrical Performance  
The sensing properties of the thin film resistance grids were characterized by measuring the temperature-dependent resistance. The SiCN resistance grid pyrolyzed at 1100 \({}^{\circ}\)C is insulated at room temperature (conductivity: \(10^{-6}\) S/m-\(10^{-4}\) S/m) [5; 26]. The electrical conductivity of the DVB-modified SiCN films was calculated from the resistance and size of the resistive grid. The room temperature conductivities of the DVB10-SiCN, DVB20-SiCN, DVB30-SiCN, DVB40-SiCN and DVB50-SiCN resistor grids are 9.4 S/m, 39.8 S/m, 32.3 S/m, 24.8 S/m and 30 S/m, respectively (Figure 6a). Compared with SiCN, the electrical conductivity of DVB-modified SiCN is significantly improved. However, when the DVB content was increased to 20%, the conductivity did not further improve. This is related to the content of free carbon in SiCN and the percolative network formed by it. In conductive composites, when the conductive phase reaches the percolation threshold, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & **SiCN** & \begin{tabular}{c} **DVB10-** \\ **SiCN** \\ \end{tabular} & \begin{tabular}{c} **DVB20-** \\ **SiCN** \\ \end{tabular} & \begin{tabular}{c} **DVB30-** \\ **SiCN** \\ \end{tabular} & \
\begin{tabular}{c} **DVB40-** \\ **SiCN** \\ \end{tabular} &
\begin{tabular}{c} **DVB50-** \\ **SiCN** \\ \end{tabular} \\ \hline \(I_{D}/I_{G}\) & 0.77 & 0.76 & 0.89 & 0.80 & 0.84 & 0.87 \\ \hline \(L_{a}\) **(nm)** & 1.118 & 1.106 & 1.198 & 1.133 & 1.630 & 1.183 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The intensity ratio of D peak to G peak \(I_{D}/I_{G}\) and carbon cluster size \(L_{a}\) obtained from the curve-fitting of Raman spectra. Figure 5: Raman spectra of SiCN films modified with different concentrations of DVB. the conductivity increases by orders of magnitude. Further increasing the concentration of the conductive phase, the conductivity increases slowly and becomes stable [27]. The percolation behavior can be attributed to the formation of free carbon network. In DVB20/SiCN the percolative network is already completely formed and it does not improve significantly in DVB50/SiCN [28]. This explains that the electrical conductivity of the two compositions is quite similar despite their DVB amounts of 20 wt% and 50 wt%, respectively. The temperature sensing properties of thin-film resistive grids were characterized by measuring temperature-dependent resistance (Figure 6b-l). Below 350 \({}^{\circ}\)C, the resistance of the SiCN resistive grid is greater than 1 G\(\Omega\), which limits the application of SiCN TFSs in the mid-low temperature range. The high conductivity of DVB-modified SiCN resistive grid makes it more suitable for sensing in the mid-low temperature range. In the temperature range of 30-400 \({}^{\circ}\)C, all DVB-modified SiCN resistive grids exhibit negative temperature coefficient of resistance, that is, the resistance decreases monotonically with increasing temperature, presenting a good sensitivity of DVB-modified SiCN resistive grids under high temperature (T) environments. The ln(1/R)-1000/T curves for the DVB-modified SiCN resistive grids were obtained according to the thermistor equation [17; 18]:  
\[ln\frac{1}{R}=c_{1}\frac{1}{T}-c_{2} \tag{2}\]  
where \(c_{1}\) and \(c_{2}\) are constants. For all SiCN resistive grids, linear behavior following the thermistor equation was obtained. The constant \(c_{1}\) values of DVB10-SiCN, DVB20-SiCN, DVB30-SiCN, DVB40-SiCN, and DVB50-SiCN thermistors are \(-372.35,-509.72,-478.65\)  
Figure 6: (**a**) Variation of SiCN conductivity at room temperature with DVB content. The resistance of film as a function of temperature: (**b**) SiCN film, (**c**) DVB10-SiCN film, (**e**) DVB20-SiCN film, (**g**) DVB30-SiCN film, (**i**) DVB40-SiCN film, (**k**) DVB50-SiCN film. A plot of resistance vs. temperature in the format ln(1/R) vs. 1000/T: (**d**) DVB10-SiCN film, (**f**) DVB20-SiCN film, (**h**) DVB30-SiCN film, (**j**) DVB40-SiCN film, (**l**) DVB50-SiCN film.