Pb/Ge(111)1×1: An anisotropic two-dimensional liquid

We report x-ray measurements of a ring of diffuse scattering due to a single layer of liquid Pb in the 1×{}1 phase of Pb/Ge(111), above 180 ^∘{}C. The ring is part of a cylinder in reciprocal space, and its radial position differs significantly from that of the first ring due to bulk liquid Pb. The ring is found to be azimuthally anisotropic, due to interaction with the substrate.