Molecular beam mass spectrometry and modelling of CH4–CO2 plasmas in relation with polycrystalline and nanocrystalline diamond deposition

Vandenbulcke, L.; Gries, Thomas; Persis, S. de; Met, C.; Aubry, Olivier; Delfau, Jean‐Louis

doi:10.1016/j.diamond.2010.03.018

Cited by 3 publications

(1 citation statement)

References 31 publications

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“…Even a small excess of CH 4 over CO 2 resulted in noticeably poorer quality material. Vandenbulcke and co-workers , have reported diagnostic and modeling studies of low pressure MW-activated C/H/O gas mixtures and of the polycrystalline diamond derived there from. For completeness, we note that the possible benefits of adding trace quantities of oxygen to C/H process gas mixtures (as O 2 or as another O containing species like CO or CO 2 ) in order to reduce nitrogen incorporation and cracking in CVD grown single crystal diamond, , and as a means of inhibiting [110] growth in heavily B-doped diamond have also been explored.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Plasma Chemistry in Microwave Chemical Vapor Deposition of Diamond from C/H/O Gas Mixtures

Kelly¹,

Richley²,

Western³

et al. 2012

J. Phys. Chem. A

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Microwave (MW)-activated CH(4)/CO(2)/H(2) gas mixtures operating under conditions relevant to diamond chemical vapor deposition (i.e., X(C/Σ) = X(elem)(C)/(X(elem)(C) + X(elem)(O)) ≈ 0.5, H(2) mole fraction = 0.3, pressure, p = 150 Torr, and input power, P = 1 kW) have been explored in detail by a combination of spatially resolved absorption measurements (of CH, C(2)(a), and OH radicals and H(n = 2) atoms) within the hot plasma region and companion 2-dimensional modeling of the plasma. CO and H(2) are identified as the dominant species in the plasma core. The lower thermal conductivity of such a mixture (cf. the H(2)-rich plasmas used in most diamond chemical vapor deposition) accounts for the finding that CH(4)/CO(2)/H(2) plasmas can yield similar maximal gas temperatures and diamond growth rates at lower input powers than traditional CH(4)/H(2) plasmas. The plasma chemistry and composition is seen to switch upon changing from oxygen-rich (X(C/Σ) < 0.5) to carbon-rich (X(C/Σ) > 0.5) source gas mixtures and, by comparing CH(4)/CO(2)/H(2) (X(C/Σ) = 0.5) and CO/H(2) plasmas, to be sensitive to the choice of source gas (by virtue of the different prevailing gas activation mechanisms), in contrast to C/H process gas mixtures. CH(3) radicals are identified as the most abundant C(1)H(x) [x = 0-3] species near the growing diamond surface within the process window for successful diamond growth (X(C/Σ) ≈ 0.5-0.54) identified by Bachmann et al. (Diamond Relat. Mater.1991, 1, 1). This, and the findings of similar maximal gas temperatures (T(gas) ~2800-3000 K) and H atom mole fractions (X(H)~5-10%) to those found in MW-activated C/H plasmas, points to the prevalence of similar CH(3) radical based diamond growth mechanisms in both C/H and C/H/O plasmas.

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