Table 1. Experimentally estimated cross sections for each dynamic process under the 60 keV electron irradiation.
The geometric mean provides a good estimate for the underlying Poisson expectation value (19). For comparison, typical elastic scattering cross sections for carbon are ~105 to 106 barn for high-angle annular dark-field (HAADF), while inelastic K-edge ionization is ~104 barn (both in EELS and energy-dispersive x-ray), and plasmon generation is ~106 barn (41). In graphene, the ratio of plasmon and core loss ionization cross sections can be much higher, up to 104 (42). The SW transition of P dopant from 55-77 to hexagonal is too fast to resolve with our imaging speed, so a lower limit is provided.
| Dopants | Dynamics | Cross sections (barn, geometric mean ± SE) |
| P | Direct exchange | 0.05 ± 0.02 |
| SW transition (hexagonal to 55-77) | ~11.2 | |
| SW transition (55-77 to hexagonal) | > 200 | |
| Replacement (by freely diffusing C adatoms) | 0.07 ± 0.02 | |
| Knockout (of PKA, the C neighbor) | 0.01 ± 0.003 | |
| N | SW transition (hexagonal to 55-77) | 0.9 ± 0.1 |
| SW transition (55-77 to hexagonal) | 22.0 ± 4.5 | |
| Al | Knockout (of PKA, the C neighbor) | ~0.25 |