Self-assembly of C-60 molecules on planar n- or p-type Si(100) has been accomplished by direct tethering onto the Si surface without using any intermediate functional hydrocarbon chain. Photoresponse has been observed on these monolayer modified electrodes in both aqueous and nonaqueous media. The p-type Si(100) surface with a bound C-60 monolayer is also capable of mediating redox reactions. These C-60 monolayer modified Si electrodes are very stable in both acidic aqueous and polar nonaqueous solvents. Characterization by fast atom bombardment mass spectroscopy (FAB-MS)suggests that simultaneous hydrosilylation and hydrogenation reactions account for the nature of the monolayer formation.