The influence of a-Si:H buffer layers on the properties of CNx materials

n the basis of ab initio calculations, the α, β- C3N4 crystalline compounds have been proposed as promising materials for optical applications in ultraviolet and visible. However, these crystalline forms of carbon nitride have been hardly obtained, mostly the formation of amorphous material being noticed. Previously, deposition of amorphous carbon nitride from a RF plasma jet operating in nitrogen with graphite electrodes was reported. This work reports on the deposition and characterisation of carbon nitride thin films by RF nitrogen plasma beam with graphite electrodes either on glass, on crystalline Si or on intermediate a-Si:H buffer layers. The layers properties (composition, crystallinity and absorption in ultraviolet, visible and infrared) have been studied by X-ray Photoelectron Spectroscopy (XPS), FTIR (Fourier Transform Infrared Spectroscopy) and UV-VIS absorption, Energy Dispersive X-ray Analysis (EDX) and X-Ray Diffraction (XRD) techniques. It is shown that amorphous carbon nitride materials with variable optical bandgap in the range 1.2-3.5 eV can be obtained. Also, the formation of an intermediate SiCN interlayer and the promotion of crystallinity in CNx films, due to buffer layer presence, is proved.