Absolute density of the argon first excited states in plasmas used for carbon deposition as determined by absorption spectroscopy

Abstract

Abstract In order to study the possible excitation transfer from argon metastables to the admixed species in an expanding cascaded arc plasma the densities of the Ar(3 p 5 4 s ) states in a deposition plasma were studied with absorption spectroscopy. For a purely argon plasma the Ar(3 p 5 4 s ) density lies in the range 10 16 –10 18 m −3 at a chamber pressure of 40 Pa. The effect on the densities of the addition of moderate amounts of methane and oxygen is small. The addition of hydrogen to the argon plasma leads to a rapid disappearance of the argon 4 s states. Possible explanations are a lowering of the argon ion density by dissociative recombination and the direct excitation energy transfer with the H ∗ ( n = 2, 3) levels.