Substrate-dependent lateral order in naphthalene-tetracarboxylic-dianhydride monolayers

The lateral order of 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA) has been investigated on different metal substrates [Ag(100), Ag(111), Ag(110), Cu(100), and Ni(111)] mainly by low-energy electron diffraction. Film preparation under appropriate conditions leads to highly ordered (sub)monolayers of NTCDA on these covalently bonding substrates. On weakly interacting Ag(111) and Ag(100), two different superstructures are observed in each case which are related to each other by a reversible phase transition. In contrast, on Ag(110) and on the more reactive Cu(100) substrate only one superstructure exists. All superstructures are commensurate with the substrate because of chemisorption on specific adsorption sites. Adsorption of NTCDA on Ni(111) does not lead to a well-ordered monolayer due to a strong local bond and hence to a lower mobility. [S0163-1829(99)01528-3].