Formative and frictional behavior of amine self-assembled monolayers

The formation of APTES (3-Aminopropyl)-triethoxysilane) self-assembled monolayers (SAMs) was studied by means of AFM and contact angle measurement, which gave the mean roughness and the static contact angle as a function of the time of film formation. Meanwhile, chemical composition and bonding energy of the SAMs were examined using X-ray photoelectron spectroscopy (XPS). Results show that APTES SAMs initially grow in island shape firstly. The 'island' grows up with reaction time and polymerization occurs among APS hydrolysis secondly. As the reaction proceeds, the mean roughness of APTES SAMs largely grows with reaction time, indicating the formation of multi-monolayers. The static contact angle measurements show that the APTES SAMs gives contact angle around 55°. The results of friction and wear test show that the APTES self-assembly monolayer can decrease the friction coefficient to silicon significantly. However, the strength of the APTES SAMs is not very good.