Diamond Chemical Vapor Deposition and Practical Applications

Abstract

Diamond chemical vapor deposition (CVD) technique has been studied intensively and has overcome some of the constraints of traditional high-pressure high-temperature (HPHT) diamond synthesis methods in the last decades. In this work, microwave plasma enhanced chemical vapor deposition (MPCVD) technique has been employed to synthesize three different kinds of crystallites of diamonds, including single crystal, polycrystalline and nanocrystalline diamonds, and to study their practical applications. Large diamond single crystals and clean diamond windows can be produced at very high growth rates, and the mechanical, chemical, optical and electronic properties of the material are extraordinary and can be tuned over a wide range. The goal is to produce large diamond single crystals for diamond anvils to make a new generation of

high-pressure-temperature experimentation to study Earth and planetary materials possible. Composite thin films of nanodiamond and silica nanotubes were synthesized on silica nanotube matrix that was seeded with nanodiamond particles. Scanning electron microscopy (SEM), Raman spectroscopy, and energy-dispersive x-ray spectroscopy (EDX) were used to analyze the composite. Wet chemical etching was applied to selectively remove exposed silica from the composites for further revealing the nanostructure of the composites. When appropriately selected sizes of nanodiamond particles were used as diamond seeds, silica nanotubes capped with CVD-grown diamond crystals were also obtained. Potential applications and implication of composites of nanodiamond and 1-D nanostructures are discussed. Fabrication of patterned diamond structures in an inexpensive way is desirable for many electrical and heat-dissipation applications. In this study, nanodiamond suspensions in ethylene glycol were used as inks for inkjet printing. By utilizing inks with optimized nanodiamond suspensions, high number density of diamond nanoparticles were laid down directly by inkjet printing to form almost continuous nanodiamond films of designed patterns on a substrate. A brief CVD process was adequate for the further growth of nanodiamond seeds to form a continuous nanocrystalline diamond film. This process allows inexpensive seeding of diamond in selected areas as well as possible formation of 1-D, 2-D, and 3-D nanodiamond structures. Details of the inkjet printing process and its potential applications will be reported.