Sn. Magonov et al., CHARACTERIZATION OF THE SURFACES OF THE CONDUCTING SALTS ALPHA-(BEDT-TTF)(2)X (X=I3, IBR2) BY SCANNING TUNNELING AND ATOMIC-FORCE MICROSCOPY, Synthetic metals, 62(1), 1994, pp. 83-89
We carried out scanning tunneling microscopy (STM) and atomic force mi
croscopy (AFM) measurements of the alpha-(BEDT-TTF)2X (X=I3 and IBr2)
salts and interpreted the results on the basis of the partial density
rho(r0, e(f)) and total electron density rho(r0) plots calculated by t
he extended Huckel tight-binding method. Large scale STM images show s
urface modifications induced by the tip-surface interactions. The STM
and AFM images show the patterns of the cation layers. The rho(r0, e(f
)) plots are essential in relating the features of the observed atomic
-resolution STM images to the surface structures and show that the eth
ylene-group hydrogen atoms of the protruded cations dominate the STM i
mages. The dependence of the STM images of the BEDT-TTF salts on the t
unneling gap resistance is probably caused by the tip-induced conforma
tional change of the ethylene groups of the surface cations.