Bonding What can be Learned for OFETs

As pointed out above, metal-organic interfaces are important because charge 

The discussion of the previous paragraphs shows that it is not enough to consider the interaction of individual molecules with the surface the overall structure of the metal-organic interface region also has a strong influence on its injection properties. This brings us to our next topic. 

Interface structures are determined by adsorbate-substrate interaetions and interactions between adsorbates, zwtralayer as well as in/cHayer. In the previous section the emphasis was placed on the molecule-substrate interaction. The present section focuses on molecule-molecule interactions and their competi-tion/cooperation with the molecule-substrate interaction, because the wealth of structures observed at organic-inorganic interfaces stems from their variable interplay. Disentangling the systematics of this interplay requires the consideration of a range of different molecules and substrates. Nevertheless, let us start again with the case of PTCDA on Ag(l 11). 

Although the structure of the PTCDA/Ag(l 11) interface is dominated by the molecule-substrate interaction (cf. the commensurate interface structure), the interaction between molecules does play an important role for the structural details and the energetics at the interface. On the one hand, there is the attractive electrostatic interaction between molecules. Because of this interaction PTCDA molecules always cluster in two-dimensional islands. However, at surface temperatures below 150 K, these islands do not yet exhibit the familiar herringbone structure [35] since the electrostatic interaction does not exhibit sufficient directional specificity, a considerable degree of structural disorder prevails, in spite of a clear propensity of the molecules to arrange in a T-like 

It turns out that even at low substrate temperatures of 100 K, the effective surface diffiision length is large enough that all molecules are able to reach an island [35], 

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