Measurements of electron densities and temperatures in low-pressure arcjet plasmas operating under diamond growth conditions

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:419808

Stalder, K R; Brinkman, E A; Jeffries, J B

The authors have measured the spatial variation of plasma parameters in a low-pressure DC arcjet plasma used in the deposition of diamond thin films. A Langmuir probe was inserted into the plasma jet from the side. Various gas mixtures were studied, including pure argon, argon-hydrogen mixtures, and argon-hydrogen-methane mixtures, with and without NO seeded into the gas as an convenient laser-induced fluorescence (LiF) probe species for gas temperature measurements. the plasma density was approximately 10{sup 10}--10{sup 11} cm{sup {minus}3} 42-mm downstream from the arcjet exit orifice. The density rose to 10{sup 12}--10{sup 13} cm{sup {minus}3} 13-mm from the orifice. The electron temperature was approximately 2 eV in pure argon, and had a high energy tail at approximately 7 eV. When hydrogen and methane was added, the electron density increased by about an order of magnitude, but these electrons were cooler, approximately 1.5 eV, with not high energy tail. Adding NO did not change the plasma density or electron temperature significantly, but it did tend to shift the plasma hydrogen concentration and distance downstream from the orifice. The authors present data for the spatial variation of these plasma parameters and compare them to the gas species and temperatures determined from laser-induced fluorescence measurements.

• OSTI ID: 419808
• Report Number(s): CONF-960634--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHEMICAL COMPOSITION
DIAMONDS
ELECTRON DENSITY
ELECTRON TEMPERATURE
PLASMA ARC SPRAYING
PLASMA DIAGNOSTICS
PLASMA JETS