We have observed interesting H-atom adsorption induced atomic rearrangements of a Pb monolayer on the Si(111) with a scanning tunneling microscope (STM). A hexagonal ring-like pattern is formed around the point defect. The interactions among nearby H-adsorbed defects can even produce interference-like superstructures. Phase boundaries are found to either enhance or suppress the formation of the interference pattern. These phenomena are produced by an intricate interplay between electronic and atomic interactions as perturbed by the adsorbed hydrogen atoms. (Physical Review Letters 94, 045505 (2005))
