EFM Study Of The Structure And Surface Potential Of Octadecvltrichlorosilane Self-Assembled Monolaver

Self-assembly, in a general sense, might be defined as the spontaneous formation of complex hierarchical structures from pre-designed building blocks, typically involving multiple energy scales and multiple degrees of freedom. Self-assembled monolayer (SAM) is ordered molecular assemblies that is formed spontaneously by the adsorption of a surfactant with a specific affinity of its headgroup to a substrate. Self-assembled monolayers exhibit optical, electrical, optoelectronical, mechanical, chemical, biochemical, or other properties for the applications of engineering. This paper studied the structure of octadecyltrichlorosilane (OTS) self-assembled monolayers by means of the electrostatic force microscopy (EFM). Our experimental results demonstrated that the structures of all OTS SAMs were not homogeneous there must be some mesoscopic scale structure inside OTS SAMs. From the viewpoint of the formation mechanism of SAM, it could be concluded that the reaction temperature is the main influence factor to the structure and growth of SAM. The electrostatic force microscopy was utilized to studied the surface potential of OTS SAM synthesized at different temperature. The results testify that when the reaction temperature is below the threshold temperature, the surface potentials of OTS SAMs are nearly the same, and when the reaction temperature is above the threshold temperature, the surface potential decreases by～5mV/℃. The change of surface potential was regarded mainly resulted from the difference of molecular packing density of SAM synthesized at different temperature.