Lateral electrical conduction in organic monolayer

Electric conductivity of organic molecules was estimated with molecular res olution using self-assembled techniques and scanning tunneling microscopy ( STM). Conjugated molecules of [1,1':4',1 "-terphenyl]-4-methanethiol (TP) w ere embedded in self-assembled monolayers of insulative n-alkanethiols, and when observed by STM, TP molecules appeared as protruding domains. The app arent height of the TP domains increases as the lateral size of the domains grows from 1 to 10 nm, reflecting the increase in the vertical conductance of the domains due to the lateral, intermolecular interaction. We assumed that the molecules are connected to each other with resistors for estimatin g the effect of intermolecular interaction on the conductance and calculate d the height of conducting disks with various radii, which should roughly r eproduce the size-dependent height of the TP domains observed by STM. The e stimated resistance of the single TP molecule was less than 40 G Omega, and the effective lateral conductivity corresponding to the large TP domains w as larger than 0.01 S/cm.