Influence of negative dc bias voltage on structural transformation of carbon nitride at 600 °C

Carbon nitride (CN) thin films were prepared at 600 °C by rf plasma pulsed laser deposition. As we increased the magnitude of the negative dc bias voltage, the CN bonds were transformed from a mixture of sp2 C–N and sp3 C–N states into a CN phase predominated by tetrahedral CN bonds. A biasing threshold of this transformation occurred due to the annihilation of the graphite microstructure, which coincided with a threshold of significant nitrogen incorporation. We found that suppression of graphite supersaturation appeared to be important for the formation of the tetrahedral sp3 C–N bonds. The nitrogen content of these films is stable upon annealing at 800 °C in vacuum.