The formation of mixed methyl/allyl monolayers has been accomplished through a two-step halogenation/ alkylation reaction on Si(111) surfaces The total coverage of alkylated Si the surface recombination velocities and the degree of surface oxidation as a function of time have been investigated using X ray photoelectron spectroscopy Fourier-transform Infrared spectroscopy and microwave conductivity measurements I he total coverage of alkyl groups the rate of oxidation and the surface recombination velocities of Si(111) terminated by mixed monolayers were found to be close to those observed for CH3-Si(111) surfaces Hence the mixed-monolayer surfaces retained the beneficial properties of CH3-Si(111) surfaces while allowing for convenient secondary surface functionalization