Molecule length-induced reentrant self-organization of alkanes in monolayers adsorbed on Au(111)

We report the observation by scanning tunneling microscopy of the reentrant self-organization of n-alkanes (CnH2n+2) in monolayers adsorbed on Au(lll) induced by a variation of the chain length. In the investigated range of lengths (10 less than or equal to n less than or equal to 38 with even n values), the presence of self-assembled monolayers which consist of a close-packed arrangement of molecules lying flat on the surface is evidenced except for alkanes with 18 less than or equal to n less than or equal to 26, The unexpected transition between ordered and disordered phases is related to the mismatch between Au(lll) :Lattice and the CH2-group period along the chain.