Velocity distributions of SiF and SiF2 in an SiF4 plasma molecular beam

Our imaging of radicals interacting with surfaces (IRIS) technique has been used to measure the velocity distributions of SiF and SiF2 molecules in an effusive SiF4 plasma molecular beam as a function of applied rf power. Modeling the kinetic data yields the corresponding translational temperatures Theta(T). The translational temperatures of both SiF and SiF2 increase with radio frequency (rf) power, from 571 +/- 180 K at 80 W to 869 +/- 54 K at 200 W for SiF, and from 427 +/- 65 K at 80 W to 557 +/- 31 K at 200 W for SiF2. These differences in Theta(T) for SiF and SiF2 indicate that the SiF4 plasma is not in full thermal equilibrium. Possible mechanisms for the trend of increasing Theta(T) with rf power are discussed by correlating SiF and SiF2 velocities with relative gas-phase densities. In addition, the effects of Theta(T) on the surface scatter coefficients for each molecule have also been addressed.