Ionic species in a silane plasma

The abundances A/sub j/ of groups of higher silane ions Si/sub j/H+/sub k/ were measured mass spectrometrically in an rf glow discharge in SiH4 under conditions used for preparation of hydrogenated amorphous silicon. The ratio A/sub j//A/sub j/-1 is about 0.3 nearly independently of j, of pressure, of degree of ionization, and of rf power. The mean hydrogen to silicon ratio for j> or =3 is 1.5 +- 0.1 and pressure independent in the 0.017--0.100-Torr range. A mechanism postulating charge or hydride ion transfer and the addition of SiH4 as the most rapid reactions of silane ions is consistent with the observations