This paper carries out the density functional theory calculations to study the adsorbate-substrate interaction between tetracene and Cu substrates （Cu （110） and Cu （100） surface）. On each of the surfaces, two kinds of geometry are calculated, namely ＇flat-lying＇ mode and ＇upright standing＇ mode. For ＇flat-lying＇ geometry, the molecule is found to be aligned with its longer molecular axis along close-packed direction of the substrate surfaces. For ＇upright standing＇ geometry, the long axis of tetracene is found to be parallel to the surface normal of the substrate on Cu （110） surface. However, tetracene appears as ＇tilted＇ mode on Cu （100） surface. Structures with ＇flat-lying＇ mode have much larger adsorption energy and charge transfer upon adsorption than that with ＇upright standing＇ mode, indicating the preference of ＇flat-lying＇ geometry on both Cu （110） and Cu （100） surface.
An investigation on the growth behavior of FePc on a Ag （110） surface is carried out by using scanning tunneling microscopy （STM）. At an FePc coverage of 3.5 ML, an ordered superstructure （densely packed） with a lateral shift is observed. The densely packed superstructure can be attributed to the substrate commensuration and the intermolecular van der Waals attractive interaction. The in-plane lateral shift in the superphase is specifically along the direction of [110] azimuth. The results provide a new perspective to understanding the intermolecular and the molecule-substrate interactions.
The reconstructed structure of Cu （100） surface induced by atomic N adsorption is studied by using scanning tunneling microscopy （STM）. The 2D structure of copper boundary between neighbouring N covered islands is found to be sensitive to the growth conditions, e.g. N＋ bombardment time and annealing temperature. The copper boundary experiences a transition from nano-scale stripe to nano-particle when the substrate is continuously annealed at 623~K for a longer time. A well-defined copper-stripe network can be achieved by precisely controlling the growth conditions, which highlights the possibility of producing new templates for nanofabrication.
