Plasma chemistry in disilane discharges

We have measured the initial silane and polysilane product yields from disilane decomposition in rf and dc discharges, at 25 and 250 °C and 20 Pa (0.15 Torr) pressure as typically used for a‐Si:H film deposition. From analyses of these yields we conclude that the initial Si₂H₆ fragmentation pattern is SiH₃+SiH₂+H (91±9%) and H₃SiSiH+2H (9±9%), that the primary product of the H+Si₂H₆ reaction is SiH₄+SiH₃, and that SiH₃ is the dominant radical causing film growth. We have measured a radical‐surface reaction probability of 0.34±0.03, very similar to that observed for SiH₃ in SiH₄ discharges. We report a spatial distribution of emission indicative of a γ‐regime discharge. From deposition on glass fibers strung between the electrodes, we find that highly strained a‐Si:H film is produced everywhere except on or near the electrodes, suggesting that energetic ion impact is necessary to yield useful films in disilane discharges.