The absorption of bromine on Cu(100) has been studied by scanning tunnellin
g 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 isla
nds 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 t
he edges of the squares. (C) 2000 Elsevier Science B.V. All rights reserved
.