The Mechanism of Diamond Nucleation from Energetic Species

Abstract

A model for diamond nucleation by energetic species (for example, bias-enhanced nucleation) is proposed. It involves spontaneous bulk nucleation of a diamond embryo cluster in a dense, amorphous carbon hydrogenated matrix; stabilization of the cluster by favorable boundary conditions of nucleation sites and hydrogen termination; and ion bombardment-induced growth through a preferential displacement mechanism. The model is substantiated by density functional tight-binding molecular dynamics simulations and an experimental study of the structure of bias-enhanced and ion beam-nucleated films. The model is also applicable to the nucleation of other materials by energetic species, such as cubic boron nitride.

Hydrogen in nano‐diamond films: experimental and computational studies

“…Coalescence of adjacent diamond crystallites most likely does not result in complete hydrogen desorption from touching surfaces leading to the incorporation of hydrogen on the touching crystallites surfaces (grain boundaries). In the case of nano-diamond film deposition form energetic species hydrogen stabilizes the nano-diamond grains as discussed in our previous studies [9,10].…”

“…The film evolves on top of a hydrogenated carbonaceous precursor containing a mixture of an amorphous and graphitic carbon formed during the first ~20 min of deposition (~300 nm thickness). When the precursor density reaches ~3 g/cm 3 , nano-diamond particles precipitate and grow to a final size of ~5 nm by means of preferential displacement of loosely bonded carbon atoms by energetic ions [9,10]. The sp 3 content of the film grown for 1 hour reaches ~80%.…”

“…2, curve b. In our previous works [9,10] we showed that the growth of the dc GD CVD film advances through the following stages: (1) graphitic film with its basal plane perpendicular to the substrate, a low H concentration and low (~2.2 g/cm 3 ) density, (2) an increase of the density followed by incorporation of hydrogen, (3) the formation of a dense (~3 g/cm 3 ), hydrogen rich layer in which diamond nucleates and grows. The hydrogen concentration in the nano-diamond film deposited by dc GD CVD increases from 3.3 × 10 21 at the nanographitic precursor region to 1.45 × 10 22 atoms/cm 3 in the ~5 nm sized nano-diamond crystallites region [12].…”

“…(3) dc GD CVD films were grown from hydrogen rich plasma (CH 4 /H 2 ratio was 9/91) by means of continuous substrate bombardment by positive hydrocarbon and hydrogen ions of ~100-200 eV kinetic energy [9,10]. No pretreatment procedure is needed to induce diamond nucleation.…”

Hydrogen concentration and bonding configuration in polycrystalline diamond films: From micro-to nanometric grain size

“…For example, the growth of nanodiamond films deposited by microwave ͑MW͒ chemical vapor deposition ͑CVD͒ from Ar-rich plasma was suggested to occur from C 2 dimers on the film surface, 10 whereas deposition from hydrogen-rich direct current ͑dc͒ energetic plasma is a subsurface or subplantation process. 11 The ability to deposit diamond films with nanoscale ordered surfaces and defined crystalline size is crucial for possible practical applications. The well-known negative electron affinity and high conductivity of diamond surfaces are properties of fully hydrogenated diamond surfaces.…”