A high-yield method has been developed for the production of hydrophilic, carboxyl-terminated alkylsiloxane monolayers on silicon using the ozonolysis and hydrolysis of 10-undecenyltrichlorosilane SAMs. Contact angles with water, a common measure of hydrophilicity, were brought to 0° on receding and approximately 16° on advancing, compared to 98° and 105° respectively before ozonation. Ellipsometry showed the presence of a full monolayer, 1 nanometer thick before ozonation, that decreases by about 0.2 nm during ozone treatment, largely due to the removal of a carbon atom in the process. This removed material coalesces as nanoparticles, observed with AFM imaging. The process has a surprisingly narrow ozone dose window, with excess ozonation resulting in complete layer removal. The carboxylate moieties allow further chemical modification of the surface.