Atomic force microscopy (AFM), contact angle, and ellipsometry measurements art : used to investigate the growth behavior of n-octadecyltrichlorosilane (OTS), n-propyltrichlorosilane (PTS), and n-triacontyltrichlorosilane (TCTS) films on hydroxylated Si(100) substrates. AFM images show that self-assembled monolayers of OTS (CH3(CH2)(17)SiCl3) grow via islands. After an initial nucleation and growth of larger primary OTS islands, smaller secondary islands grow in the areas between the primary islands until the film is complete. The shape and size of the islands and the progress in growth are not well-defined, however, and depend upon the film preparation conditions. In contrast, shorter-chain PTS molecules (CH3(CH2)(2)SiCl3) do not appear to demonstrate this island growth behavior during film formation. Longer-chain TCTS molecules (CH3(CH2)(29)SiCl3) show an island-type of growth with different island structures compared to those observed for OTS. We discuss the differences in growth behavior observed under cleanroom and normal laboratory conditions.