Scanning tunnelling microscopy and low-energy electron diffraction were used to study the adsorption and subsequent thermal desorption of molecular sulfur from the Si(001) surface. Room-temperature adsorption of sulfur resulted in the formation of an overlayer, displaying a high density of vacancies or defects, with the underlying Si(001) surface retaining the (2 x 1) reconstruction. Annealing this surface to 325C led to the desorption of the sulfur overlayer and the appearance of coexisting c(4 x 4) and (2 x 1) surface reconstructions. The data suggested that the c(4 x 4) reconstruction was an adsorbate-induced structure in which the sulfur created defects during the desorption process. High-resolution filled- and empty-state images of the c(4 x 4) surface suggested a missing-dimer defect model for this reconstruction. Sulfur-Induced c(4 x 4) Reconstruction of the Si(001) Surface Studied by Scanning Tunnelling Microscopy. P.Moriarty, L.Koenders, G.Hughes: Physical Review B, 1993, 47, 15950-3