Ultimately, the selectivity in intrinsically selective AS-ALD is determined by the chemoselectivity of the precursor (i.e., faster reactivity on the GS) leading to a nucleation delay on the NGS (Fig. .d). Thus, reactivity differences on GS and NGS are the focus for computational investigations. The first study by Kwon et al. investigated the selective ALD of Co on silicon. It was shown experimentally that the precursor only reacts with the H-terminated silicon surface (GS) while the OH-terminated surface (NGS) does not react (Fig. ). This was explained with catalytic hydrogenation of the precursor by the H-Si( ) surface. The computational study reveals the thermodynamic driving force and the lower reaction barrier for the reaction on the GS (Fig. ). Reprint with permission from reference .