ATOMIC STRUCTURES OF AG ISLANDS ON SI(001)(2X1)

Atomic structures of the three-dimensional (3D) Ag islands and the gro wth mode of Ag grown on Si(001)(2 x 1) have been studied by coaxial im pact collision ion scattering spectroscopy. At room temperature (RT), Ag grows in Stransky-Krastanov (SK) mode. Although the crystallinity i s not good, the 3D Ag islands have a structure of Ag(011)/Si(001) with an interlayer spacing between the first and third layers of d(13) = 2 .80 Angstrom. After the sample grown at RT was annealed at 600 degrees C, the two-dimensional (2D) Ag layer disappeared and the 3D Ag island s are reconstructed to a structure of Ag(001)//Si(001) and Ag[100]//Si [100] with a good crystallinity. The interlayer spacing between the fi rst and third layers was d(13) = 4.09 Angstrom. For deposition at a su bstrate temperature of 600 degrees C, Ag also grows in SK mode and the 3D Ag islands have a structure of Ag(001)//Si(001) and Ag[100]//Si[10 0]. We found that our results on the 2D Ag layer support the surface u nwetting due to the free energy difference between the 2D layer and th e 3D islands, and the surface unwetting characterizes the behavior of the Ag on the Si(001) surface. (C) 1998 Elsevier Science B.V.