SCANNING TUNNELING MICROSCOPE STUDY OF THE STRUCTURAL TRANSFORMATION OF THE SI(111)7X7 SURFACE TO THE NA-INDUCED 3X1 SURFACE

The structure of the Na-induced Si(111) 3 x 1 surface has been studied using a field-ion-scanning-tunneling-microscope. The STM images showed that the entire Si surface was uniformly covered with a single layer of atomically resolved Na 3 x 1 structure. Upon annealing, the Na layer peeled off gradually, revealing the underlying Si substrate, which exhibited various intermediate reconstructions such as 2 x 2, 5 x 5, and 9 x 9 before the 7 x 7 structure was restored at 800-degrees-C. Our observations suggest that the top layer of the Si substrate converts to the bulk terminated 1 x 1 structure upon Na deposition and annealing.