ELSEVIER Thin Solid Films 258 ( 1995) 75 -81 Nanotribological characterization of hydrogenated carbon films by scanning probe microscopy Zhaoguo Jiang, C.-J. Lu, D.B. Bogy, C.S. Bhatia”, T. Miyamoto** zyxwvutsrqponmlkjihgf Computer M echanics Laboratory, Department of M echanical Engineering, University of California at Berkeley, CA 94720, USA Received 20 April 1994; accepted 14 September 1994 Abstract Mechanical and tribological properties of hydrogenated carbon films were evaluated using three newly developed nanotribological characterization techniques based on scanning probe microscopy, including nano-hardness tests and nano-wear tests using a point contact microscope and nano-friction tests using a friction force microscope. It was found that the nanoindentation hardness decreases with increase of hydrogen content in the films, and the substrate influence on the hardness values is not significant for indentation depths less than a quarter of the thickness of the carbon films. The critical load for wear on the friction force versus loading force curve also decreases with hydrogen concentration, whereas the nano-wear depth and the nano-friction coefficient increase. Our results show that the three characterization methods are very effective in determining mechanical or tribological properties of ultrathin films and optimizing the fabrication process parameters. Keywords: Atomic force microscopy; Coatings; Hydrocarbons; Tribology 1. Introduction Due to their superior properties, amorphous carbon films have been widely used as protective films in the hard disk industry. These properties include high hard- ness, good wear resistivity, low static and dynamic friction coefficients, chemical inertness, low cost, pro- cess simplicity, good process control, and coating ho- mogeneity [ 11. Carbon films used in magnetic media applications can be fabricated by several processes [2]. In every case, the physical properties of films change with process parameters, and it is important to under- stand the relationship. This has led to extensive studies over the last two decades. A variety of techniques have been used to identify microstructures of amorphous carbon films, including Raman spectroscopy [ 31, Fourier transform infrared spectroscopy [4], electron spectroscopy for chemical analysis [5], electron energy loss spectroscopy [6], nuclear magnetic resonance [7], *Storage Systems Division, IBM Corporations, San Jose, CA 95193, USA. **On leave from the Kaneko Research Laboratory at the NTT Interdisciplinary Research Laboratories. 0040-6090/95/$9.50 d: 1995 - Elsevier Science S.A. All rights reserved SSDlOO40-6090(94)06376-I optical measurements [ 81, transmission electron micro- scopy [9], and X-ray photoemission spectroscopy [5]. The main concerns in magnetic media applications are the mechanical and tribological performances of the films. Several limited techniques for the mechanical and tribological characterization of amorphous carbon films have been reported. These include hardness measure- ments by microhardness indenters [lo], scratch tests [ 111, pin-on-disk tests [ 121, contact start-stop tests or drag tests [ 131, and chemical reactivity tests [ 141. How- ever, the current development trend in the hard disk industry is to fabricate ultrathin carbon films with thicknesses only 50-400 A in order to reduce magnetic spacing and increase storage capacities. For such thin films, limitations of the above-reported methods are exposed. Nanomechanical and nanotribological charac- terizations of films are hence believed to be critical in determining tribological performance and optimizing the process parameters of the films. Recently, several nanotribological characterization methods for thin solid films have been developed based on scanning probe microscopy, such as nanoindentation hardness tests and nano-wear tests using a point contact microscope, and nano-friction tests using a friction force