Backbone‐Length‐Optimized Inhibitors Deliver Long‐Retention Selectivity in Area‐Selective ALD of VO ₂

ABSTRACT Area‐selective atomic‐layer deposition (AS‐ALD) relies on surface inhibitors; however, their molecular design remains empirical owing to the lack of a unified framework linking the molecular structure to inhibition performance. In this study, we systematically investigate the influence of the carbon‐backbone length of trimethoxyphenyl(alkyl)silane small‐molecule inhibitors (SMIs) on adsorption behavior and selectivity in the AS‐ALD of VO ₂ . We use density functional theory to show that SMI adsorption on hydroxylated SiO ₂ proceeds through a multistep pathway involving physisorption and single‐ and double‐bonded chemisorption. Longer backbones enhance physisorption via stronger dispersion interactions; however, they impose rapidly increasing kinetic barriers to form a stable double‐bonded configuration owing to severe steric and conformational constraints. Random sequential adsorption simulations show that the achievable surface coverage is dictated by a tradeoff between the molecular packing density and steric exclusion, resulting in a nonmonotonic dependence on the backbone length. These coupled chemical and geometric effects define the optimal intermediate backbone‐length range. This prediction is validated by VO ₂ AS‐ALD experiments, in which only intermediate‐length SMIs maintain high selectivity (> 90%) over extended cycling. This study establishes a predictive and chemically and geometrically grounded design principle for molecular inhibitors in AS‐ALD, and broadly for area‐selective atomic‐layer processing.