Fluorinated benzalkylsilane molecular rectifiers.

We report on the synthesis and electrical properties of nine new alkylated silane self-assembled monolayers (SAMs) - (EtO)Si(CH)N = CHPhX where n = 3 or 11 and X = 4-CF 3,5-CF, 3-F-4-CF, 4-F, or 2,3,4,5,6-F, and explore their rectification behavior in relation to their molecular structure. The electrical properties of the films were examined in a metal/insulator/metal configuration, with a highly-doped silicon bottom contact and a eutectic gallium-indium liquid metal (EGaIn) top contact. The junctions exhibit high yields (>90%), a remarkable resistance to bias stress, and current rectification ratios (R) between 20 and 200 depending on the structure, degree of order, and internal dipole of each molecule. We found that the rectification ratio correlates positively with the strength of the molecular dipole moment and it is reduced with increasing molecular length.