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Exploring the plasma chemistry in microwave chemical vapor deposition of diamond from C/H/O gas mixtures.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Kelly, Mark W. Richley, James C. Ashfold, Michael N. R. Mankelevich, Yuri A. |
| Copyright Year | 2012 |
| Abstract | 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. |
| File Format | PDF HTM / HTML |
| DOI | 10.1021/jp306190n |
| PubMed reference number | 22924542 |
| Journal | Medline |
| Volume Number | 116 |
| Issue Number | 38 |
| Alternate Webpage(s) | http://www.chm.bris.ac.uk/pt/diamond/pdf/jpca116-9431.pdf |
| Alternate Webpage(s) | https://doi.org/10.1021/jp306190n |
| Journal | The journal of physical chemistry. A |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
