Dissociation rates of silane in an RF discharge by tunable diode laser absorption

Effective dissociation rates have been measured for silane diluted in argon at low pressure (0.2-0.3 torr) in a low power (1-2 watt) RF discharge at 13.6 MHz. The discharge tube consists of three parallel, wire-mesh electrodes with the center electrode driven. Gas flow is through the electrode mesh. The effective dissociation rate is determined by monitoring the decrease in the I.R. absorption of an isolated silane line as a function of gas residence time in the discharge. Absorption is measured just downstream from the discharge. The data show an initially high rate which drops to near zero for long residence times. Both the relative concentration at which dissociation ceases and the initial rate depend on RF power