Faceting of the two-fold decagonal Al71.8Ni14.8Co13.4(0 0 1 1̄ 0) surface studied by He diffraction

The two-fold decagonal-Al71.8Ni14.8Co13.4(0 0 1 1̄ 0) surface is investigated by highly surface sensitive He atom scattering. The diffraction pattern shows that the topmost surface layer preserves a perfect quasi-crystalline ordering expected from the bulk. The surface is found to develop facets with (1 0 0 0 0)-equivalent orientation, inclined by 18° to the original surface. The facets are of sufficient size to observe diffraction from them. The facet planes are identical to those identified in an as grown sample.