Atomic-Scale Imaging of Dopant Atom Distributions within Silicon δ-Doped Layers

We report measurements of the distribution of Sb atoms in δ-doped Si, over a wide 2-D concentration range. Both annular dark-field imaging and electron energy loss spectroscopy proved sufficiently sensitive to locate Sb atoms at the atomic scale. Improvements in both detector sensitivities and specimen preparation were necessary to achieve these results, which offer a surprising explanation for the dramatic difference in electrical activity between 2-D and 3D dopant distributions at the same effective volume concentrations. The prospects for the general identification of individual dopant atoms will be discussed.