Abstract: By using AFM, the process of the OTSmonolayer formation on glass substrate surface by self assembly from 1×10^-3 mol/L OTStoluene solution at 18 ℃ was revealed. The analyses of AFMimages as well as the surface mean roughness R_a of the sample surfaces indicated that, after 15 min reaction a smooth OTSmonolayer with a R_a of 0.156 nm/4 μm² could be obtained on the glass surface. However, this freshly formed OTSmonolayer was unstable, as the reaction proceeds, the R_a of the monolayer would slightly increase within the succeeding 15 min, and finally keep a constant value about 0.170 nm/4 μm² even for 2 h reaction. The advancing contact angle measurement showed that after~15 min reaction, a completely hydrophobic surface formed with an advancing contact angle of 105°. Our research also showed that during the initial reaction period, most of the adsorption molecules just adsorbed on the substrate surface physically. But some kinds of very strong combination between a few of adsorption molecules and the substrate surface was established, which was much stronger than physical interaction.

Key words: Octadecyltrichlorosilane(OTS), Self-assembled monolayer, Atomic force microscope(AFM)