Hydrophobic CN x thin film growth by inductively-coupled RF plasma enhanced pulsed laser deposition

Abstract

Interest in carbon nitride as a wear-resistant coating has spurred a large number of attempts at thin film growth using a variety of techniques. Unfortunately, achieving the proper stoichiometry has proven to be surprisingly difficult, and significant effort is typically required to obtain nitrogen contents in excess of 25%. We report the achievement of 38% nitrogen content films deposited on (100) silicon substrates by means of pulsed laser ablation of a graphite target in conjunction with an inductively coupled RF nitrogen plasma source originally designed for molecular beam epitaxy growth of GaN. Quadrupole mass spectroscopy of the plasma source, yields a cracking efficiency of approximately 1.8%, with no significant dependence on RF power. Strong trends in nitrogen incorporation, with both substrate temperature and laser fluence, are observed, the best films being grown at temperatures less than 300°C and fluences of less than 410 mJ/cm 2. No discernable trend in nitrogen content is observed with either laser repetition rate or the RF power applied to the nitrogen plasma source, and only CN single bonds are in evidence in FTIR. Contact angle measurements indicate that moderate nitrogen content CN x films have a slightly hydrophobic character, comparable to pure amorphous carbon films. Coupled with the hardness potential of this material, the hydrophobic behavior makes CN x a candidate for a number of applications, including alleviating stiction problems in rotating component microelectronic machine (MEMS) systems.