Ordered Mn-diluted Au/Si(111) reconstructions

Using scanning tunneling microscopy, effects produced by adsorption of less than 0.1 monolayer of Mn on Au/Si(111) reconstructions have been studied. It has been found that small amounts of Mn eliminate the original 5 x 2-Au and alpha-root 3 x root 3-Au reconstructions and initiate formation of new ordered structures 8 x 2, 10 x 2, and 2 root 21 x 2 root 21R +/- 10.9 degrees, which are essentially the Au/Si(111) reconstructions with dilute Mn. The Mn concentration in these structures is as small as one or two Mn atoms per unit cell, i.e., it varies from 0.012 to 0.1 ML of Mn. Scanning tunneling spectroscopy has demonstrated that the 2 root 21 x 2 root 21 is plausibly metallic, while the 8 x 2 and 10 x 2 are semiconducting. The latter reconstructions can be considered as possible prototypes for the low-dimensional dilute magnetic semiconductors. (C) 2011 Elsevier B.V. All rights reserved.