At ALD conditions for PE-ALD of Ru and Co, it is reasonable to consider that the surface termination can change from H-termination to NHx-termination via the reaction with plasma generated •N, •H, •NH, and •NH2 radicals and we consider the chemistry on this surface next. In Fig. (a), for RuCp2, the overall reaction energy is positive for transfer of surface and bridging hydrogen on the NHx-terminated Si(100) surface, making CpH elimination clearly unfavourable. After the first CpH formation and desorption, the computed reaction energy is 0.83eV for H transfer from surface NH2 and 1.53eV for H transfer from bridge NH. The computed reaction energies for the 2 nd H transfer continues to be positive for both types of H transfer: after formation of the 2 nd CpH, the computed reaction energy is as high as 3.62eV for H transfer from surface NH2 and 1.79eV for H transfer from bridge NH.