Atomic structures of Ag islands on Si(001)(2x1)

Atomic structures of the three-dimensional (3D) Ag islands and the growth mode of Ag grown on Si(001)(2 x 1) have been studied by coaxial impact collision ion scattering spectroscopy. At room temperature (RT), Ag grows in Stransky-Krastanov (SK) mode. Although the crystallinity is 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 islands are reconstructed to a structure of Ag(001)//Si(001) and Ag[100]//Si[100] with a good crystallinity. The interlayer spacing between the first and third layers was d(13) = 4.09 Angstrom. For deposition at a substrate 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[100]. We found that our results on the 2D Ag layer support the surface unwetting due to the free energy difference between the 2D layer and the 3D islands, and the surface unwetting characterizes the behavior of the Ag on the Si(001) surface. (C) 1998 Elsevier Science B.V.