INTERPRETATION OF SCANNING TUNNELING AND ATOMIC-FORCE MICROSCOPY IMAGES OF TCNQ SALTS

The surfaces of the TCNQ salts TFF-TCNQ, Qn(TCNQ)2, 4EP(TCNQ)2 and TEA (TCNQ)2 (TCNQ = tetracyanoquinodimethane, TTF = tetrathiafulvalene, Qn = quinolinium, 4EP = 4-ethyl-N-methylpyridinium, TEA = tri-ethylammon ium) were examined by scanning tunneling microscopy (STM) and atomic f orce microscopy (AFM). The STM and AFM images of these salts were inte rpreted on the basis of the rho(r0, e(f)) and rho(r0) plots of their m olecular layers calculated with the extended Huckel tight-binding elec tronic structure method. The present work shows that a close interplay between experiment and theory is necessary for the rational surface a nalysis with STM and AFM.