DEPOSITION OF CARBON NITRIDE THIN-FILMS IN A HYBRID RF-PLD TECHNIQUE

In a hybrid r.f.-PLD technique pulsed laser deposition (PLD) in combin ation with a capacitively coupled r.f. substrate bias with nitrogen as processing gas was used to synthesize CNx films with nitrogen content s up to x = 0.31. The r.f. bias leads to the formation of a glow disch arge in the processing gas, from which N-2(+) ions were accelerated on to the growing film owing to the negative d.c. self-bias voltage of th e substrate electrode. Ion current densities at the substrate were typ ically in the order of 30 mu A cm(-2). X-ray photoelectron spectroscop y (XPS) measurements on films showed an increasing amount of nitrogen with increasing ion current density and d.c. bias voltage as well as w ith decreasing substrate temperature. Two different electronic states can be distinguished in the C 1s and N 1s XPS spectra, which can be at tributed to an sp(2) and sp(3) hybridization of carbon in carbon nitri de. The corresponding Raman spectra show two features around 1350 cm(- 1) and 1550 cm(-1), typical for disordered carbon. The incorporation o f nitrogen in the films is confirmed by Fourier transform infrared (FT IR) spectroscopy which reveals similar features to those of the Raman spectra, normally forbidden in FTIR spectra. Atomic force microscopy r eveals an increasing average roughness and a decreasing microhardness with increasing substrate temperature. With increasing pulse repetitio n rate the roughness and microhardness increase, saturating for high p ulse repetition rates with similar functional dependence. (C) 1998 Els evier Science S.A.