Adsorption of Ag on the Si(111)root 3 x root 3-Au surface

Thermal properties and atomic arrangements of Ag adsorbates at coverages be tween 0.1 and 0.8 ML on the Si(1 1 1)root3 x root3-Au surface have been stu died by means of low energy electron diffraction (LEED), scanning tunneling microscopy, and Rutherford backscattering spectroscopy (RBS). In particula r, the two surface structures of 6 x 6 and 2 root3 x 2 root3 are newly obse rved with LEED. The Ag minimal coverages determined with ex situ RBS measur ements are 0.15 and 0.25 ML for the 6 x 6-(Au,Ag) and 2 root3 x 2 root3-(Au ,Ag) surfaces, respectively. The Si(1 1 1)6 x 6-(Au,Ag) surface shows a rev ersible phase transition between 6 x 6 at room temperature and 2 root3 x 2 root3 at 150 degreesC. STM images for both the 6 x 6-(Au,Ag) and 2 root3 x 2 root3-(Au,Ag) surfaces show p1 symmetry. The 2 root3 x 2 root3 periodicit y is found additionally in the STM image of the 6 x 6-(Au,Ag) surface at sa mple biases lower than 0.5 V. Based on these results, the relationship betw een the 6 x 6-(Au,Ag) and 2 root3 x 2 root3-(Au,Ag) surfaces is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.