Abstract
Aging Effects of one-layer Langmuir-Blodgett (LB) films of 2-alkyl-7,7,8,8-tetracyanoquinodimethane (alkyl-TCNQ) have been investigated by means of infrared (IR) and atomic force microscopy (AFM). Time-dependent infrared (IR) reflection-absorption (RA) spectral changes of a one-layer LB film of pentadecyl-TCNQ on a gold-evaporated glass slide indicate that the alkyl chain becomes more tilted with respect to the surface normal while the TCNQ plane becomes more perpendicular with time. Similar time-dependent changes in the molecular orientation were observed also for a one-layer LB film of pentadecyl-TCNQ on a CaF2 plate and for one-layer LB films of dodecyl-TCNQ on the gold-evaporated glass slide and CaF2 plate. However, one-layer LB films of octadecyl-TCNQ did not show a significant change in the molecular orientation. Time-dependent changes in the AFM image of a one-layer LB film of pentadecyl-TCNQ on mica show that the thickness of the LB film varies from 4.6 to 8.2 nm during the time course from 15 to 180 minutes after film deposition.
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