It was recalled that the √19 x √19 surface reconstruction was induced at the Si(111) surface by introducing a small amount of Ni adsorbate. The √19 x √19 reconstruction was extensively studied using Auger electron spectroscopy, reflection high-energy electron diffraction and scanning tunnelling microscopy. The first successful preparation was reported, of √19 x √19, by melting small particles of Ni onto the Si(111) surface in the scanning tunnelling microscopy chamber. The scanning tunnelling microscopic observations of the resultant √19 x √19 showed that there were 2 types of domain in √√19 x √19, and these were found to be twin-oriented. A simple crystallographic argument showed that a pair of twin-oriented unit cells was possible in √19 x √19. The present scanning tunnelling microscopic observations also showed that 7 x 7, 1 x 1-RC and √19 x √19 phases appeared in this order as the Ni content increased. The 1 x 1-RC phase was heterogeneously nucleated along a lower step edge of the Si(111) sample, while the √19 x √19 phase was homogeneously nucleated on the terrace.

Scanning Tunnelling Microscope Studies on Twinned Atomic Structures of √19 x √19 Surface Reconstruction in the Ni/Si(111) System. G.Kinoda, K.Ogawa: Surface Science, 2000, 461[1-3], 67-77