Adsorption of Si2Cl6and Si2H6on epitaxially grown CaF2/Si( 111) was investigated by core level and valence band photoemission. CaF2surfaces that were first photoactivated with intense synchrotron radiation showed enhanced molecular adsorption indicating that patterned deposition of silicon may occur. Attempts to chemical vapor deposit Si with these molecular precursors under elevated temperatures revealed that Si2H6was able to sustain Si growth on the CaF2epitaxy, while Si2Cl6adsorption terminated after — 1 monolayer of deposition. Possible explanations for this behavior are presented. © 1990, American Vacuum Society. All rights reserved.