Evidence of supersonic flow in an arc-heated diamond film deposition reactor

• Published in: Diamond and related materials Vol. 5; no. 2; pp. 134 - 140
• Main Authors: Young, Robert M., Schreurs, Jan J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.1996; Elsevier
• Subjects: Arc jet; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Nozzles; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Pilot; Plasma applications; Plasma processing; Pilot; Nozzles; Arc jet; Plasma processing; Supersonic flow; CVD; Plasma; Plasma jets; Nonmetals; Diamonds; Crystal growth from vapors; Experimental study; Chemical reactors; Electric arcs; Film growth
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/0925-9635(96)00474-8

A Pilot impact tube was used to measure the flow velocity in a laboratory d.c. arc-heated diamond deposition reactor at 35 Torr. Speeds up to Mach 1.32 ± 0.09 were found, with the bracketing error in the measurement representing alternative interpretations according to equilibrium or frozen chemistries. Radial traverse across the reactor showed peak Mach numbers along the centerline, as expected for a free jet into a relatively stagnant ambient. As the surrounding fluid is entrained, it slows the jet, cools it, and spreads it out, such that the centerline Mach number at the substrate location drops to M≈0.3. Theory has indicated that optimal diamond film growth rate and quality will result in arc jet reactors if the Mach number is around sonic, M = 1. Here we have tested the flow field downstream of an arc jet issuing from a converging-diverging nozzle, establishing experimentally that regions in our diamond reactor indeed have M > 1. We believe that this is the first reported experimental measurement of such a high velocity in a diamond reactor.