Submonolayer- and monolayer-coverage structures of K/Si(100)

Using scanning tunneling microscopy we have measured K on Si(100)2×{}1 from low coverages (0.1-monolayer K) up to saturation coverage (1-monolayer K) deposited at room temperature. In the low-coverage range we have observed a structure with local order, where the atomic features are arranged in mostly threefold periodicity of the Si lattice along the rows of Si dimers. Upon increase of the coverage the surface develops a 2×{}3 reconstruction, where the initial dimer structure of the substrate is preserved. At saturation the surface is covered with a two-dimensional K layer. The possibility of tunneling with sample bias voltages in the mV range indicates the presence of states at the Fermi level and the metallic character of the K surface layer.