M. C. T. Garcia, T. Utsunomiya, T. Ichii
Dec 20, 2019
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Journal
Japanese Journal of Applied Physics
Abstract
The surface potentials of 1-hexadecanethiol [HDT: CH3(CH2)15SH] and 1-hexadecanol [HDO : CH3(CH2)15OH] self-assembled monolayers (SAMs) were measured with reference to a 1-hexadecene [HD : CH3(CH2)13CH=CH2] SAM using Kelvin probe force microscopy. These molecules possess the same hydrocarbon chain length but vary in the covalent bond formed with the silicon substrate (Si–S, Si–O and Si–C). Micropatterned SAMs were used to eliminate the effects of surface potential variation of the probes. Surface potential contrasts against the reference HD SAM were measured to be −72 mV and −45 mV for HDT and HDO SAM respectively. These results agree qualitatively with surface potentials of the SAMs predicted from dipole moments of the molecules grafted to silicon as estimated by Molecular Orbital Package semi-empirical computations. The surface potential is found to be a result of dipoles formed by the adsorbed molecule as well as the interfacial bond between molecule and substrate.