γ-mercapto-propyl trimethoxysilane （MPTS） and γ-methacryloxy propyltrimethoxysilane （MPTES） were self-assembled on a hy- droxylated glass substrate to form a two-dimensional organic monolayer （MPTS-MPTES SAM）. The terminal thiol groups （-SH） in the MPTS-MPTES SAM were in-situ oxidized into sulfonic acid groups （-SO3H） to endow the film with good chemisorption ability. Then rare earth （RE） （lanthanum-based） composite thin films were prepared by self-assembly technique based on the as-prepared SAM, taking advantage of the chemisorption ability of the sulfonic acid groups. Automatic force microscope （AFM）, X-ray photoelectron spectrometry （XPS）, contact angle measurement and ellipsometer were used to characterize MPTS-MPTES/RE composite films. The macrofriction and wear behaviors of the films sliding against an AISI-52100 steel ball were examined on a unidirectional friction and wear tester, and the worn surface morphologies were observed on an AFM. The results showed that MPTS-MPTES/RE films had a low friction coefficient （0.09） and a long wear life （5980 sliding pass） at a light load （50 mN）. It indicated that the superior tribological properties of the MPTS-MPTES/RE composite films were attributed to the special characteristic of RE elements, the mobility of the films and good bonding strength.
Silane coupling regent （3-mercaptopropyl trimethoxysilane （MPTS）） was prepared on the single-crystal silicon substrate to form 2-dimensional self-assembled monolayers （SAMs）. The growth behavior of SAMs formed from 3-MPTS was investigated using atomic force microscopy （AFM）, contact angle measurements, ellipsometry, and X-ray photoelectron spectroscopy （XPS）. The formation behavior of MPTS SAMs was investigated by a series of AFM images and the roughness of MPTS SAMs on silicon substrates with the assembling time from 1 min to 24 h. The water contact angle measurements indicated the growth behavior of MPTS that correlated with the AFM measurements at different immersion times, too. The chemical states of the typical elements in the MPTS SAMs were analyzed using X-ray photoelectron spectroscopy. The results show that MPTS is self-assembled on the substrate.
