X-ray reflectivity of the Cu(110) surface

The specular reflectivity from the (110) surface of a copper single crystal was measured for temperatures between 300 and 1100 K. At lower temperatures the reflectivity is well described by a model that yields a contraction of the spacing between the first and the second surface layers by 8% relative to the bulk layer separation. The fits also show large surface-normal vibrational amplitudes within the first few atomic layers. The line shape of the scattering transverse to the specular direction has two components below 1000 K and evolves with increasing temperature. Present data do not preclude the existence of a surface-roughening transition.