The gaseous species produced by the electron beam evaporation of silicon from conventional copper and carbon hearths were studied by utilizing a residual gas analyzer. At low evaporation rates about 13% of the silicon evaporates as molecules containing two to seven atoms. The percentage of clusters increases only slightly with rate, indicating that their heat of evaporation differs only slightly from that of the silicon atoms. Additional molecules, predominantly Si2C, occur if vitreous carbon liners are used. The resulting carbon contamination of the amorphous silicon films (about 1.5 mol.%) was confirmed by electron microprobe analysis. A discussion is given concerning the influence of cluster deposition on the growth of amorphous silicon films. © 1977.