Phonons Localized at Step Edges: A Route to Understanding Forces at Extended Surface Defects

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Science  12 May 1995:
Vol. 268, Issue 5212, pp. 847-850
DOI: 10.1126/science.268.5212.847


Inelastic helium atom scattering has been used to measure the phonons on a stepped metallic crystalline surface, Ni(977). When the scattering plane is oriented parallel to the step edges and perpendicular to the terraces, two branches of step-induced phonons are observed. These branches are identified as transversely polarized, step-localized modes that propagate along the step edge. Analysis reveals significant anisotropy in the force field near the step edge, with all forces near the step edge being substantially smaller than in the bulk. Such measurements provide valuable information on metallic bonding and interface stability near extended surface defects.