Effect of substrate strain on adsorption

Direct evidence for the effect of local strain at a surface on the bonding strength for adsorbates is presented. Scanning tunneling microscopy revealed that adsorbed oxygen atoms on Ru(0001) surfaces are located preferentially on top of nanometer-size protrusions above subsurface argon bubbles, where tensile strain prevails, and are depleted around their rim in regions of compression, relative to the flat surface. Such effects can be considered as the reverse of adsorbate-induced strain, and their direct local demonstration can be used to test theoretical predictions.