Evaluation of structures in C/sub 18/TCNQ Langmuir-Blodgett ultrathin films with and without adsorbed donors using attenuated total reflection method

The structures are investigated using attenuated total reflection (ATR) for octadecyl-7,7',8,8'-tetracyano-quinodimethane (C/sub 18/TCNQ) Langmuir-Blodgett (LB) ultrathin films with and without adsorbed electronic donors of p-phenylenediamine (PD) and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). The thickness of the LB films is determined by theoretical curve fitting to the ATR curves assuming the dielectric constant of the LB films. The obtained thickness of the LB films without adsorbed donors is much larger than the molecular length of C/sub 18/TCNQ. This is thought to be caused by the formation of bimolecular layers in the LB films. In contrast, LB films with adsorbed donors have monomolecular layered structure.