Plasma chemistry aspects of a-Si:H deposition using an expanding thermal plasma

The plasma chemistry of an argon/hydrogen expanding thermal arc plasma in interaction with silane injected downstream is analyzed using mass spectrometry. The dissociation mechanism and the consumption of silane are related to the ion and atomic hydrogen fluence emanating from the arc source. It is argued that as a function of hydrogen admixture in the arc, which has a profound decreasing effect on the ion-electron fluence emanating from the arc source, the dissociation mechanism of silane shifts from ion-electron induced dissociation towards atomic hydrogen induced dissociation. The latter case, the hydrogen abstraction of silane, leads to a dominance of the silyl (SiH 3 ) radical whereas the ion-electron induced dissociation mechanism leads to SiH x (