Observation of a nanoscale chessboard superstructure in the Br-Cu(100) adsorbate system

The absorption of bromine on Cu(100) has been studied by scanning tunnelling microscopy. At bromine coverages below that required to saturate the well-known c(2 x 2) reconstruction, a novel mesoscopic superstructure is formed by gently annealing a room-temperature-exposed surface. This involves islands of a new c(2 x 2)-Br reconstruction of typical dimension 20 Angstrom x 20 Angstrom interspersed with regions of bare Cu(100) to produce a striking nanoscale chessboard pattern characterised by monoatomic step heights at the edges of the squares. (C) 2000 Elsevier Science B.V. All rights reserved.