A new striped-phase of decanethiol self-assembled monolayers on Au(111) formed at a high solution temperature

Self-assembled monolayers (SAMs) of decanethiol (C10) on Au(1 1 1) prepared at room temperature (RT), 60 degrees C, and 70 degrees C have been investigated using high resolution scanning tunneling microscopy (STM). For SAMs prepared at RT, the c(4 x 2) superlattice of the basic (root 3 x root 3) R30 degrees structure was hardly observed in small-scale STM images. Increasing the solution temperature to 60 degrees C results in formation of SAMs having large ordered domains of the c(4 x 2) superlattice. In contrast to the previous studies, our results indicate the presence of four different topographical heights for the C10 molecules per c(4 x 2) unit cell. Preparation of C10 SAMs from 70 degrees C of solution temperature leads to the formation of new striped phase with (4 root 3 x 2 root 3) R30 degrees unit cell. The area of a single molecule in the (4 root 3 x 2 root 3) R30 degrees striped structure amounts to 57.73 angstrom(2), which is about 167% larger than that (21.6 angstrom(2)) for a molecule in the c(4 x 2) structure. (C) 2012 Elsevier B.V. All rights reserved.