Optimization of nitrogenated amorphous carbon films deposited by dual ion beam sputtering

Optimization of deposition conditions for nitrogenated amorphous carbon (a- C:N) films prepared by a dual ion beam sputtering (DIBS) technique is repor ted. A ripple structure was observed on the surface of a-C:N films, which w as believed to be corresponding to the off-normal incidence bombardment by N ions during deposition. Infrared spectra indicated that the nitrogen atom s incorporated were bonded as C-N, C-N and C=N in the carbon network. The r elative intensity of D and G bands obtained by fitting the Raman spectra sh owed that the sp(3) content in the a-C:N films increased as the Ar ion ener gy was increased and the sp(3) content was the highest with 100 eV N ion bo mbardment. The maximum micro-hardness achieved was about 25 GPa for the 200 nm thick a-C:N films deposited under the optimized conditions. The compres sive stress ranged from 1 to 3 GPa. The optical band gap determined by spec tral ellipsometry ranged from 0.6 to 1.0 eV. The refractive index and extin ction coefficient at 633 nm wavelength were about 2.14 and 0.22 for the fil ms deposited under the optimized conditions, respectively. Hardness, stress and optical band gap measurements showed a similar trend with the relative intensity of I-D/I-G. (C) 1999 Elsevier Science S.A. All rights reserved.