Effect of bias voltages on the synthesis of nanostructured carbon nitride films

XPS, Raman scattering and SEM were used to study effect of DC bias voltages (0-400 V) on the synthesis of high nitrogen content of carbon nitride (CNx) films. Maximal N/C ratio up to 0.81 was first obtained at the bias voltage of 250 V, and the maximal fraction of sp3 CN bond inside the film was up to 40%. Either too high or too low bias voltages would result in decrease of nitrogen content inside the CNx films. Typical G and D bands were identified. Intensities of G and D bands showed periodic development following an increase of bias voltages. Several groups of nanoscale particles were observed at the pulsed bias voltage of 5 kV. Each group of particles appeared sunflower type of distribution where the biggest (85 nm) particle at the center was surrounded by many small sizes (35 nm) of CN particles.