• An atom's diameter is about 1-5 Angstroms, or .1 - .5 nm.
• Silicon atoms have 16 atoms arranged into a diamond structure. The silicon atom diameter is 1.175 Å, the silicon interatomic distance is 2.3 Å and the lattice content is 5.4307 Å.
• Silicon has a molecular density of 5.02 x 10^22 atoms / cm^3. Roughly, this means about 2.93 x 10^22 atoms / cm^2, or 2.93 x 10^8 atoms / nm^2.
• See also this Intel announcement on 65 nm feature size

-- MattWalsh - 24 Nov 2003