Ball and stick model of a δ-doped Si:P layer viewed along the  direction. Thirty-two layers in the  direction are shown. Si atoms (small gray spheres), P atoms (large dark gray spheres), covalent bonds (gray sticks), repeating cell boundary (solid line).
Drumm et al. Nanoscale Research Letters 2013 8:111 doi:10.1186/1556-276X-8-111