Hydrogen poor cationic silicon clusters in an expanding argon-hydrogen-silane plasma

Cationic silicon clusters SinHm+ with up to ten silicon atoms have been detected mass spectrometrically in an expanding argon-hydrogen-silane plasma used for fast deposition of amorphous hydrogenated silicon. A reaction pathway is proposed in which initial silane ions are produced by dissociative charge exchange between argon and hydrogen ions emanating from the plasma source and the admired silane followed by chain reactions of the created ions with silane. The silicon clusters are hydrogen poor, which is ascribed to the high gas temperature as the initial argon-hydrogen plasma is thermal in origin. (C) 1998 American Institute of Physics. [S0003-6951(98)00819-5].