Influence of ambient gas on diamond-like carbon films prepared by KrF pulsed laser deposition

We have studied the diamond-like carbon (DLC) and carbon nitride (CN) thin films deposited by KrF excimer laser (248 nm) ablation under various ambient gas conditions. DLC thin films were deposited on quartz and Si(100) substrates in pure hydrogen and helium gas at laser fluence of 2-10 J/cm(2). Optical absorption measurements show that the DLC films prepared in a H, atmosphere of 800 mTorr with 8 J/cm(2) have an optical band gap of 2.0 eV. The tetrahedral amorphous carbon (ta-C) films deposited in helium gas have an optical band gap of approximately 1.0 eV. Incorporation of nitrogen atoms in the DLC films showed marked change in the optical properties when the N-2 mixture ratio in hydrogen exceeded 50%. The composite layered structures consisting of DLC and CN were formed to investigate the optical property in stacked CN films. Laser-induced fluorescent technique was used to study the dynamics of C-2 molecules produced by pulsed laser deposition at various ambient gas conditions. (C) 2001 Elsevier Science B,V. All rights reserved.