| Abstract
| - We used scanning tunneling microscopy (STM) to observe the bc-surface of the triethylammonium-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)2)charge-transfer complex crystal, which is terminated with the arraysof TCNQ chains. Three kinds of distinct structures of the quasi-one-dimensional (1D) TCNQ chains werefound on different surface terraces, that is, the TCNQ molecules within a chain exhibit the monomerization,tetramerization, and octamerization, respectively. Each structure corresponds to a respective electron densitydistribution along the chain direction. The latter two reflect the different characteristics of the bulk and surfaceenergy-band filling, respectively. The monomer structure indicates that the single molecular orbital was probedby STM due to the weakening of the overlapping between TCNQ molecules induced by the enlarging of theintermolecular distance. The two-dimensionality of the surface exerts an apparent influence on the quasi-1DTCNQ chains, with the specific manifestation of enhancing the interchain coupling even at the cost of theweakening of the intrachain interaction.
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