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

Abstract

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 Ess 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 565 K. A quantitative dependence of Ess 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.