Controlled growth of crystalline g-C3N4 nanocone arrays by plasma sputtering reaction deposition

Vertically and neatly arranged crystalline graphitic C3N4 (g-C3N4) nanocone arrays were firstly synthesized on nickel-covered silicon (1 0 0) substrates supported on a graphite frame. Synthesis was accomplished using an abnormal glow discharge plasma sputtering reaction deposition method with a feed gas mixture of CH4, N2 and H2. The experimental results show that the morphologies, structures, composition and photoluminescence of the grown nanostructures strongly depend on the CH4/(N2 + H2) ratios (0-1/10). The hexagonal g-C3N4 nanocone arrays were well grown at a CH4/(N2 + H2) ratio of around 1/150 as a result of the hydrogen ion sputtering of the graphite frame to generate a lot of carbon atoms, the hydrogen ion etching on the growing graphite structures, and the reaction between the active nitrogen atoms and the sputtered carbon atoms. The g-C3N4 nanocone arrays have the characteristic photoluminescence-peak of g-C3N4 and very nice wettability to the polymer absorber layers. At the higher or lower CH4/(N2 + H2) ratios, the silicon or diamond nanocone arrays were grown respectively due to the ion-sputtering of the silicon substrate and the inhibition of CHn-radicals on the H+-sputtering of the graphite frame or the mismatch between the sputtered carbon atoms and the dissociated nitrogen atoms.