Bonding at the K/Si(100) 2×1 interface: A surface extended x-ray-absorption fine-structure study

Using surface extended x-ray-absorption fine-structure spectroscopy we establish the K-Si bond length to be 3.14±{}0.10 {} at the K/Si(100) 2×{}1 interface for (1/2-monolayer K coverage. This value corresponds to the sum of the Si and K covalent radii and suggests weak interaction of K with the substrate relative to the interaction along the K chains on the surface. This finding, while consistent with earlier studies of this system, disagrees with recent total-energy pseudopotential calculations which determine a K-Si distance of 2.59 A{}.