Local-strain mapping on Ag(111) islands on Nb(110)

The local in-plane strain of Ag(111) islands on the Nb(110) surface has been derived from the lateral variation of the electronic density of states measured by scanning tunneling spectroscopy. The onset energy E-ss of the Shockley-type surface-state band is shifted to higher energies compared to the bulk due to thermal strain arising from the difference in thermal expansion between Nb and Ag and cooling by 565K. A quantitative dependence of E-ss from the strain is obtained by density-functional theory calculations. This allows a mapping of the local strain of individual Ag islands on the nanometer scale