Scanning tunneling microscopy (STM) images of Ag films grown on Ru(0001) reveal a periodic unit cell with a structural transformation at silver coverages slightly less than one monolayer. Dislocations in the overlayers are similar to the Au(111) herringbone structure; however, Ag/Ru(0001) exhibits two novel differences from previously observed herringbone structures. First, the unit cell dimensions change dramatically as a function of coverage. Second, STM images of Ag/Ru(0001) are inverted relative to those for Au(111). We show that this image inversion is due to substantial relaxations perpendicular to the surface resulting from local strains in the silver overlayer.

• Received 19 June 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.4242