Spectroscopic analysis of a -C and a -CN x films prepared by ultrafast high repetition rate pulsed laser deposition J. Appl. Phys. 97, 073522 (2005); 10.1063/1.1874300 Effects of thermal annealing on the structural, mechanical, and tribological properties of hard fluorinated carbon films deposited by plasma enhanced chemical vapor deposition This paper consists of an investigation of the structural arrangement of the sp 2 phase in amorphous unhydrogenated carbon nitride ͑a-CN x ͒ films and its effect on their physical properties. The a-CN x films ͑0.16Ͻ x Ͻ 0.25͒ were synthesized using a hybrid deposition system combining laser ablation of graphite and a source of atomic nitrogen. The microstructure of the films was investigated by Raman spectroscopy and electron paramagnetic resonance ͑EPR͒, while their optical and mechanical properties were determined by spectroscopic ellipsometry and nanoindentation, respectively. It was found that deposition at high laser intensities leads to an increase in the spin density ͑Ͼ10 20 /cm 3 ͒ and the EPR linewidth ͑of a few gausses͒ along with a decrease in nitrogen content. Visible Raman measurements indicate that these effects are accompanied by an increase in the degree of disorder of the sp 2 phase, as inferred from the broadening and downshift of the G Raman band, and a reduction of the CN triple bond signal. The analysis of these results in terms of the structural configuration and bonding in the films, show that an enhancement of the connectivity of the sp 2 phase in the layers, takes place when deposition is performed at high laser intensities. These structural modifications are strongly correlated to a decrease in the optical gap from 0.61 to 0.21 eV as well as to an increase of the hardness value of the films from 12 to 24 GPa. The transition from a reduced to an enhanced connectivity of the sp 2 phase occurs when the nitrogen content decreases below 22 at. %, as a result of the detected reduction of the triply bonded CN species in the layers.

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In this work, the nitrogen molecular dissociation level in Ar/N2 surface-wave plasma is evaluated as a function of plasma parameters such as Ar percentage in the gas mixture, power absorbed in the plasma, and total pressure in order to design an efficient N-atom source that can be used for various applications such as thin-film deposition and materials surface modification. This plasma is operated at 40.68 MHz and the nitrogen dissociation rate is determined, in the remote plasma, by analyzing the optical emission of the first positive molecular nitrogen band. For all operating conditions, the dissociation rate ([N]/[N2]) of N2 molecules was enhanced, as the percentage of Ar in the mixture increased from 0 to ∼95%, and dissociation rates higher than 2.5% were measured. This gain in the dissociation rate became more pronounced when the plasma power and total pressure increased from 40 to 120 W and from 4 to 7.5 Torr, respectively. These results are discussed in terms of the kinetics of the electrons, nitrogen atoms, and molecules and confirm theoretical kinetic models presented in the literature.

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