Molecule synthesis in an Ar-CH4-O2-N2 microwave plasma

The formation of new mols. in a microwave plasma, created from a mixt. of Ar, CH4, N2 and O2, is investigated by means of an in-depth study of the mol. abundance in the plasma. The mols. are detected by means of tunable diode laser absorption spectroscopy and by abs. mass spectrometry. Three groups of mols. can be discerned in terms of mol. abundance: CO is predominantly formed, together with H2O, N2 and H2. The mols. CH4 and O2 are significantly depleted, but still abundant in a finite quantity. The third group is formed by several other species like NH3, NO, HCN etc. This tendency is expected to occur in every low temp. plasma contg. C, O, H and N atoms. Furthermore, the combination of both techniques also allows us to make a clear distinction between the etching mode and deposition mode of the microwave reactor. Etching mainly occurs when the ratio of admixed gas flows F(O2)/F(CH4) > 0.5. [on SciFinder (R)]