Ion fragmentation of methylsilane by a hot tungsten wire in a Freeman-type ion source was investigated with low-energy mass separated ion beam apparatus for the study of catalytic chemical vapor deposition (Cat-CVD) processes. The mass analysis showed that dominant fragment ions were typically H1+, H2+, H3+, CH3+, SiH+, and SiCH4+. The ion production rates, which depended strongly on the tungsten wire temperature, decreased with time due to modification of the tungsten wire surface during the process. The x-ray diffraction and x-ray photoelectron spectroscopic measurements showed that silicon carbide, carbon, and tungsten carbide compounds were formed on the tungsten wire surface during the process.
