A new striped-phase of decanethiol self-assembled monolayers on Au(1 1 1) formed at a high solution temperature

Self-assembled monolayers (SAMs) of decanethiol (C10) on Au(1 1 1) prepared at room temperature (RT), 60 °C, and 70 °C have been investigated using high resolution scanning tunneling microscopy (STM). For SAMs prepared at RT, the c(4 × 2) superlattice of the basic image structure was hardly observed in small-scale STM images. Increasing the solution temperature to 60 °C results in formation of SAMs having large ordered domains of the c(4 × 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 × 2) unit cell. Preparation of C10 SAMs from 70 °C of solution temperature leads to the formation of new striped phase with image unit cell. The area of a single molecule in the image striped structure amounts to 57.73 Å2, which is about 167% larger than that (21.6 Å2) for a molecule in the c(4 × 2) structure.