The following series of STM images illustrates the surface restructuring of S/W(111) associated with an overlayer-induced (4x4) reconstruction. The saturation S coverage is ~0.5 monolayers in all cases. The S is deposited from gaseous H₂S.
 
 

Figure 1. The surface morphology shown in Figure 1 and Figure 2 with the same dimensions (1000Å x 1000Å) results from annealing at temperatures of ~875K and ~1075K, respectively. Tunneling current: 1.2nA, Sample Bias: +1V

Figure 2. The arrows indicate a representive domain boundary in a terrace (due to misalignment of (4x4) unit cells from both sides) as well as an isolated local defect. Tunneling current: 1.2nA, Sample Bias: +1V

Figure 3. This is a representative STM image (with dimensions of 33Å x 33Å) showing the atomic structure of the (4x4) unit cells, one of which is highlighted with a box. Each top triangular cluster (having 6~7 atoms) corresponds to individual bright spots in Figures 1 or 2. Tunneling current: 1.2nA, Sample Bias: +0.1V

 Reference
 1. C.-H. Nien, I.M. Abdelrehim, and T.E. Madey, Surf. Rev. & Lett., Vol. 6, # 1 (1999), in press.