THERMAL-BEHAVIOR OF MIXED-STACK CHARGE-TRANSFER FILMS OF 2-OCTADECYL-7,7,8,8-TETRACYANOQUINODIMETHANE AND 3,3',5,5'-TETRAMETHYLBENZIDINE PREPARED BY THE LANGMUIR-BLODGETT TECHNIQUE AND DONOR DOPING .2. MORPHOLOGY AND ANNEALING EFFECTS OF THE FILMS INVESTIGATED BY ATOMIC-FORCE MICROSCOPY AND ULTRAVIOLET-VISIBLE NEAR-INFRARED AND INFRARED SPECTROSCOPIES

Morphology and annealing effects of Langmuir-Blodgett (LB) films of a mixed-stack charge transfer (CT) complex of 2-octadecyl-7,7,8,8-tetrac yanoquinodimethane (octadecyl-TCNQ) doped by 3,3',5,5'-tetramethylbenz idine (TMB) have been investigated by atomic force microscopy (AFM) an d ultraviolet-visible-near infrared (UV-vis-NIR) and infrared (IR) spe ctroscopies. AFM images of the LB films of the CT complex scanned at r oom temperature show that the films consist of numerous one-dimensiona l needle-like microcrystals and that a periodic structure exists insid e these needle-like microcrystals. A cyclic thermal treatment on one-, three-, and 11-layer films of the CT complex up to 110 degrees C, whi ch is below their dedope temperatures, makes the needle-like microcrys tals thinner and flatter while the molecular arrangement and structure in the crystals are nearly unchanged. However, when the temperature o f the CT complex films is elevated above their respective dedope tempe ratures, the needle-like microcrystals become much thinner, resulting in the formation of place-like microcrystal domains which are characte ristics of LB films of octadecyl-TCNQ. The molecular arrangement and s tructure in the CT complex films after the annealing above the dedope temperature differ from those before the annealing and seem to exist i n two different forms. One is just like that of LB films of octadecyl- TCNQ, while the ether is neither like that of the CT complex films bef ore the annealing nor like that of the LB films of octadecyl-TCNQ.