Symmetry and rotational epitaxy of incommensurate Xe layers on Pt(111)

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Abstract
High-resolution He diffraction studies of the structure and rotational epitaxy of incommensurate Xe layers on Pt(111) are reported. At completion of the commensurate (√3 × √3 )R30° monolayer (C) a continuous phase transition to a striped incommensurate phase (SI) occurs. With increasing incommensurability the striped phase (SI) transforms at a critical misfit of ≃6.5% to a hexagonal incommensurate phase (HI) in a first-order transition. Upon further increase of the misfit (≥7.2%) the HI phase displays a continuous transition from an aligned to a Novaco-McTague rotated orientation (HIR). Xe on Pt(111) appears to be an ideal model system of two-dimensional phases and their mutual transitions, i.e., it is the first system showing completely the theoretically predicted sequence of C→SI→HI→HIR transitions.