Superhard diamondlike carbon: preparation, theory, and properties

Abstract

One of the many forms of carbon, diamondlike carbon (DLC) or tetrahedral amorphous carbon (ta-C) consists mainly of sp3 bonded carbon atoms. If properly prepared, DLC can have properties that rival those of crystalline diamond. The beneficial properties of DLC stem from the continuous rigid random networks of sp3 carbon atoms, and the properties can essentially be tailored by controlling the sp3/sp2 ratio. Techniques that have been successfully used to prepare high quality DLC coatings or thin films include pulsed laser ablation, filtered cathodic vacuum arc deposition, and mass selected ion beam deposition. Diamondlike carbon coatings that possess properties close to diamond in terms of hardness, atomic smoothness, infrared transparency, and chemical inertness can be processed easily with these techniques. In the past decade, tremendous progress has been made in experimental and theoretical investigations of hydrogen free DLC. Experimental and commercial applications in areas including microelectronics, microtribology, and biomedical technologies have been demonstrated. Potential applications include sensors, flat panel displays (field emitters), and photodiodes. Past and recent developments in synthesis and processing, properties, and modelling of hydrogen free superhard amorphous DLC are comprehensively reviewed. The techniques of fabrication, theoretical modelling, physical and mechanical characterisation, properties, and present and potential applications of DLC are discussed.