Growth mechanism of vapor-deposited diamond

Abstract

An elementary-reaction mechanism of diamond growth by a vapor deposition process is proposed. The central postulate is that the main monomer growth species is acetylene. The mechanism basically consists of two alternating steps: surface activation by H abstraction of a hydrogen atom from a surface carbon and the addition of one or two acetylene molecules. During the addition reaction cycle a number of solid C–C bonds is formed and hydrogen atoms migrate from a lower to an upper surface layer. The mechanism is in general agreement with the macroscopic views of the Russian researchers and is consistent with the numerous experimental observations reported in the literature.

Diamond growth by chemical vapour deposition

“…When the low reactivity of methane is taken into account, only CH 3 and C 2 H 2 are left as likely growth species under typical diamond CVD conditions. Several mechanisms for diamond CVD have been proposed, including CH 3 -based mechanisms [81,82], Acetylene-addition mechanisms [83], Combined CH 3 -C 2 H 2 mechanism [83].…”

Growth on the reconstructed diamond (100) surface

“…Briefly, a methyl radical adds at a radical site formed from abstraction of one or both of the trough hydrogens (see Figure 3e). This step is followed either by abstraction of the other trough hydrogen and one of the methyl hydrogens (Reactions d or f and k after Reaction c) or by abstraction of a methyl hydrogen (Reaction 1 after Reaction s) to give the C 6 B structure, which has a carbon atom that bridges the trough. For reasons discussed below, we allow the trough mechanism to occur only adjacent to C 6 -type sites just formed by the dimer mechanism, as shown in Figure 3e.…”

“…The resulting structure, C 6 HH, is shown in Figure 3e. C 6 HH is generated when a Q species is formed directly in front of or behind (eclipsing) a C 6 T* species, which has a radical site at the top carbon (Figure 3d Because AG < 0 for Reaction M, it is effectively irreversible (assuming that we have not omitted some other etching reactions of C 6 HH which could convert it back to C5), and C 6 HH ultimately covers half a monolayer. The rate of formation of that half-monolayer would correspond to an effective linear growth rate of around 7 microns/hour.…”

“…In the past few years several detailed growth mechanisms have been proposed to explain the chemical vapor deposition (CVD) of diamond films [1][2][3][4][5][6][7][8][9][10]. In general, these models have used the formal resemblance between the bonding and structure in diamond and in alkanes to postulate [6] that chemistry on the diamond surface could be understood in terms of the very well known chemistry of alkanes.…”

“…In general, these models have used the formal resemblance between the bonding and structure in diamond and in alkanes to postulate [6] that chemistry on the diamond surface could be understood in terms of the very well known chemistry of alkanes. In effect, the assumption is made that the chemistry of a diamond surface is controlled by the local electronic environment, as is true for alkanes, and that bulk band structure and surface states play no role.…”