Characterization of amorphous carbon nitride by bottom-gated thin-film structure

We describe the characterization of nitrogen-incorporated amorphous carbon (a-C:N) films by using a double beam method. The carrier transport of a-C:N films deposited at various substrate temperatures was investigated using a bottom-gated thin-film transistor (TFT). At substrate temperatures below 300 °C, the optical band gap (E_opt) and the Raman intensity ratio between the D (∼1360 cm^{- 1}) and G (∼1590 cm^{- 1}) peaks (I_D / I_G) of an a-C:N film deposited at room temperature were observed to vary only marginally from 1.9 eV and 0.88, respectively. The electrical conductivity of the a-C:N film increased by more than four orders of magnitude with an increase in the substrate temperature from 150 to 300 °C due to an improvement in the activation of the nitrogen-incorporated a-C film caused by the thermal annealing effect. Based on the E_opt and I_D / I_G values, we concluded that this behavior is not responsible for the change in the hybridization of carbon atoms. The a-C:N based TFT exhibited an ambipolar transport with the strong p-type operation. The field effect hole mobility (μ_h) attained a value as high as 1.7 × 10^{- 4} cm²/Vs. In this study, one of the important results is that μ_h increased with the substrate temperature due to the increase in film conductivity. We found that the highest success yield of transistor operation of 38% was obtained from the a-C:N TFTs deposited at a substrate temperature of 290 °C.