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. Fil m preparation under appropriate conditions leads to highly ordered (sub)mon olayers of NTCDA on these covalently bonding substrates. On weakly interact ing 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 su perstructure exists. All superstructures are commensurate with the substrat e because of chemisorption on specific adsorption sites. Adsorption of NTCD A on Ni(111) does not lead to a well-ordered monolayer due to a strong loca l bond and hence to a lower mobility. [S0163-1829(99)01528-3].