The CVD of Nanodiamond Materials

Abstract

The growth and characteristics of nanocrystalline diamond thin films with thicknesses from 20 nm to less than 5 mm are reviewed. These materials contain between 95% and >99.9% diamond crystallites, the balance being made up from other forms of carbon. Within this class of materials there is a continuous range of composition, characteristics, and properties which depend on the nucleation and growth conditions. It is convenient to classify these films as either ultra-nanocrystalline-diamond (UNCD) or nanocrystalline-diamond (NCD) based on their microstructure, properties, and growth environment. In general, UNCD materials are composed of small particles of diamond ca. 2-5 nm in size with sp 2 -carbon bonding between the particles. UNCD is usually grown in argon-rich, hydrogen-poor CVD environments, and may contain up to 95-98% sp 3 -bonded carbon. NCD materials start with high density nucleation, initiating nanometer-sized diamond domains which grow in a columnar manner with the grain size coarsening with thickness. NCD is generally grown in carbon-lean and hydrogen-rich environments. NCD and UNCD exhibit an interesting range of physical properties which find use in X-ray windows and lithography, micro-and nanomechanical and optical resonators, tribological shaft seals and atomic force microscopy (AFM) probes, electron field emitters, platforms for chemical and DNA sensing, and many other applications.

Boron-doped ultrananocrystalline diamond synthesized with an H-rich/Ar-lean gas system

“…[7,25] For example, even 1-3% CH 4 /H 2 ratio would result in up to 50% sp2 impurities. [27]. However, the present study demonstrates that UNCD, especially BD-UNCD can be achieved not only in H-rich/Ar-free gas system, but also in a gas system with a high concentration of methane (up to 10%), which underscores the fact that a CH 4 /H 2 ratio is not crucial for diamond quality.…”

“…Diamond film synthesis begins with substrate seeding with commonly used seeding processes such as surface mechanical abrasion with diamond particles or sonication with slurries containing suspended diamond nanoparticles, [27]. A high density of diamond particles (usually 10 9 -10 12 /cm 2 ) on the substrate ensures appropriate seeding density which accelerates the onset of deposition and provides for a more uniform growth rate and thickness across the substrate.…”

Metallic Seed Nanolayers for Enhanced Nucleation of Nanocrystalline Diamond Thin Films

“…[43][44][45] In fact, all the synthesized NCD films in this study are of a lower crystalline order than the strongly faceted NCD films with high purity grown from extremely high diamond seed densities and carbon-lean gas atmosphere, 2 and they are commonly referred to as 'ballas' or cauliflower-type diamond. 2,39 The smoothest NCD films with most uniform surface morphology were grown on the Mo, Nb, and W metallic thin films (Figures 7b, 7c, and 7f, respectively). In these three cases, the cauliflower-like structures are limited to lateral dimensions of several hundreds of nanometers only.…”

Luminescent nanodiamonds for biomedical applications

“…HPHT synthesis reproduces these conditions in the laboratory using large presses capable of achieving similar high pressures and temperatures in a controlled environment (Bundy et al 1955;Field 1992). In CVD synthesis, hydrocarbon gas mixtures are ionised and, through a series of reactions, the carbon atoms are deposited onto a substrate to grow diamond films (Angus et al 1993;Spear and Dismukes 1994;Butler and Sumant 2008;Balmer et al 2009). DND forms in a process where carbon-containing explosives are detonated in the absence of oxygen.…”