A novel method to derivatize silicon surfaces with 3-mercaptopropylsilane molecules has been developed and optimized. This method is based on an argon flow that increases the evaporation rate of the silane molecules by lowering the partial pressure of the silane molecules in gas phase above the liquid silane, at room temperature. X-ray photoelectron spectroscopy studies of the surfaces showed a dense monolayer coverage as well as hydrolysis of the silane methoxy groups. Atomic force microscopy was used to investigate the roughness of the surfaces after each step of the derivatization process. Since the final surface has a measured surface roughness of 0.19 nm, this method will be especially useful for further synthetic routes and advanced single molecule detection studies of interactions on surfaces as well as improvement of existing conventional techniques for surface derivatization and analysis.