Laser approaches for deposition of carbon nitride films — chemical vapour deposition and ablation

• Published in: Diamond and related materials Vol. 8; no. 2; pp. 577 - 581
• Main Authors: Popov, C, Jelinek, M, Ivanov, B, Tomov, R.I, Kulisch, W
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.1999
• Subjects: Ablation; Laser; LCVD; Nitride; Nitride; Ablation; LCVD; Laser
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/S0925-9635(98)00372-0

The deposition of carbon nitride films by laser-induced chemical vapour deposition (LCVD) from the system NH 3/CCl 4 and by laser ablation of a graphite target in nitrogen atmosphere has been studied. Two types of lasers were used: a copper bromide vapour laser for LCVD and an eximer KrF laser for the ablation process. The first laser source has a set of parameters (wavelengths, repetition rate, pulse duration) which makes it unique in material processing. During the ablation deposition an additional DC discharge (ignited by each shot) or RF discharge (permanent) was utilised to increase the reactivity of the nitrogen. The deposition rate for LCVD is almost one order of magnitude higher than for the laser ablation (0.050–0.350 and 0.025–0.040 nm/pulse, respectively) due to the direct laser impact on the substrate surface. The composition of the layers was studied by Auger electron spectroscopy (AES) and wavelength dispersive X-ray analysis (WDX). For the laser ablation the N/C ratio increases when an additional DC or RF discharge was used compared to the non-assisted process. Maximum values are reached at nitrogen pressures twice lower for RF discharge than for DC discharge assisted deposition. In the case of LCVD the composition depends mainly on the laser power. Chemical bonding was investigated by Fourier transform infrared (FTIR) spectroscopy. The FTIR spectra of the films deposited by LCVD show well defined bands which are superimposed to a broad peak for samples prepared by laser ablation. At higher RF plasma power a weak band around 2200 cm −1 appears in the spectra which can be attributed to the stretching mode of triple bonded C–N. Such a peak is not observed in cases of DC discharge and LCVD.