Formation of OTS self-assembled monolayer on glass surface investigated byAFM

By using AFM, the process of the OTS monolayer formation on glass substrate surface by self-assembly from 1x10(-3) mol/L OTS-toluene solution at 18 de grees C was revealed. The analyses of AFM images as well as the surface mea n roughness R-a of the sample surfaces indicated that, after 15 min reactio n a smooth OTS monolayer with a R-a of 0.156 nm/4 mu m(2) could be obtained on the glass surface. However, this freshly formed OTS monolayer was unsta ble, as the reaction proceeds, the R-a of the monolayer would slightly incr ease within the succeeding 15 min, and finally keep a constant value about 0.170 nm/4 mu m(2) even for 2 h reaction. The advancing contact angle measu rement showed that after similar to 15 min reaction, a completely hydrophob ic surface formed with an advancing contact angle of 105 degrees, Our resea rch also showed that during the initial reaction period, most of the adsorp tion 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 physica l interaction.