Structural relaxation of adlayers in the presence of adsorbate-induced reconstruction:: C60/Cu(111) -: art. no. 125405

We revisit submonolayer growth Of C-60 on Cu(111) by scanning tunneling microscopy (STM), with emphasis on the formation of higher-order commensurate metastable states. These phases show concomitant interfacial reconstruction, adlayer buckling, and adlayer rotation in order to match as closely as possible the 10.0 Angstrom C-60 nearest neighbor (NN) distance. Most interestingly, a clear correlation between the adlayer rotation angle and molecular contrast patterns is demonstrated. This is caused by the C-60-induced reconstruction at preferred binding sites and adlayer buckling in adjustment to strain. Four contrast patterns, i.e., "disordered maze," "linear-wall maze," "p(root7 x root7)," and "p(2 x 2)," with increasing C-60 NN distances are categorized. In the most compressed phase, buckling is favored and it is analogous to the ground state of a strongly-coupled antiferromagnetic system on a triangular lattice with alike adlayer buckling and interfacial corrugation. In contrast, the molecular orderings in the other structures are mostly dictated by lateral displacements of C-60 toward preferred reconstructive binding sites. These metastable phases thus illustrate structural relaxation of a molecular layer on an adsorbate-induced reconstructed substrate in different adsorbate-adsorbate and adsorbate-substrate interaction limits.