(313a) Self-Assembled Diamond Nanocrystals

The initial stages in the growth of diamond from the vapor phase can lead to the appearance of dense, ordered arrays of diamond nanocrystallites. When diamond is condensed from a methane-hydrogen plasma onto (001) epitaxial iridium, orientationally-ordered (001) diamond nanocrystallites appear at a density 10¹² cm^-2. They occur on the Ir surface after a rapid cooling brought about by abrupt termination of the plasma. The crystallite sizes are highly monodisperse, typically with lateral size 7 nm and mean interparticle spacing 14 nm [1]. The emergent diamond crystals form a weakly ordered triangular lattice with correlation lengths of several lattice parameters. It is possible to explain the pattern formation as a result of depletion interactions that occur during diamond growth from a disordered carbon matrix. Because the crystallite density is so high, subsequent evolution leads to rapid coalescence within a few minutes, resulting in a smooth, continuous film that covers the substrate. When the growth step is extended in time, thick single crystal plates can be produced. These observations are useful for understanding diamond nucleation and growth as well as for developing reliable heteroepitaxial growth processes.

[1] C. Bednarski, Z. Dai, A-P Li, and B. Golding, Diamond Relat. Mater. 12, 241 (2003); B. Golding, C. Bednarski-Meinke, and Z. Dai, Diamond Relat. Mater. 13, 545 (2004).