Scanning tunneling microscopy images of transition-metal structures buried below noble-metal surfaces

We analyze scanning tunneling microscopy (STM) experiments of Ir impurities and chains buried in the subsurface layer of Cu(001) by first-principles calculations based on the density-functional theory and show for the first time that metal atom defect structures below a metal surface can be detected by STM. We show that this is not particular to the Ir/Cu system, but applies to a much wider class of systems, and holds also for defects in deeper layers. For the Ir/Cu system we confirm by total energy calculations that the subsurface position is energetically the most favorable one.