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 fora‐Si:H film deposition. From analyses of these yields we conclude that the initial Si2H6fragmentation pattern is SiH3+SiH2+H (91±9%) and H3SiSiH+2H (9±9%), that the primary product of the H+Si2H6reaction is SiH4+SiH3, and that SiH3is 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 SiH3in SiH4discharges. We report a spatial distribution of emission indicative of a &ggr;‐regime discharge. From deposition on glass fibers strung between the electrodes, we find that highly straineda‐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.