Growth mode and electrical conductance of Ag atomic layers on Si(0 0 1) surface

The difference in growth mode of Ag films at room temperature between on Si(0 0 1)-2×1 clean and Si(0 0 1)–2×3-Ag surfaces was studied by four-probe electrical resistance measurements, reflection-high-energy electron diffraction, low-energy electron diffraction, ultraviolet photoelectron spectroscopy and scanning tunneling microscopy. A peculiar change in resistance was observed during deposition of Ag on the 2×1 surface; the electrical resistance rose temporarily around 40 ML coverage, and then, it dropped steeply due to percolation among Ag islands. On the other hand, only a slow resistance drop was observed during Ag deposition on the 2×3-Ag surface. This difference in changes of electrical resistance was revealed to relate to the difference in Ag growth styles. Ag grew in island-growth mode with three-dimensional (3D) islands of Ag(1 1 1) and Ag(0 0 1) orientations up to around 40 ML coverage on the 2×1 surface, and Ag(1 1 1) islands dominated and percolated each other beyond this coverage. On the other hand, Ag grew only with Ag(0 0 1) 3D islands on the 2×3-Ag surface, among which the percolation occurred more slowly by further deposition.