CNx-layers prepared by plasma assisted chemical vapour deposition

CNx-layers were prepared by plasma assisted chemical vapour deposition methods (PACVD) with capacitively or inductively coupled plasma using different carbon precursors (CO, C2H2, CH4, C-2(CN)(4), fullerene). The composition, structure and chemical bonds depend highly on precursor and deposition conditions. The layers were predominantly amorphous. With CO as precursor the N/C ratio in the layers was close to that of C3N4. Small crystallites have been found in some layers by transmission electron microscopy, the electron microdiffraction patterns fitted to those predicted for the beta-C3N4 and for a rhombohedral C3N4 phase. First experiments with fullerenes as carbon precursor resulted in layers with a N/C ratio up to 0.9. The carbon was mainly sp(3) hybridized. With hydrogen containing precursors NC ratios up to 0.9 have been measured at temperatures below 600 K. The hydrogen content was high. Higher temperatures led to harder layers and lower nitrogen contents. Using tetracyanoethylene soft layers were obtained with a N/C ratio up to 0.7 and a high content of cyanogroups.