Destabilization of Sn²⁺ 5s² Lone-Pair States of SnO through Dimensional Crossover

Abstract

Materials exhibiting unique electronic properties arising from a characteristic crystal structure have physical properties that are sensitive to structural dimensionality. This study involves the destabilization of Sn 5s2 lone-pair states of SnO films by decreasing their structural dimensionality in the out-of-plane direction. The inherent dispersive band structure of the SnO films remained unchanged between 80 and 11 nm. Below 11 nm, their dispersive band structure disappeared, the O/Sn ratio increased, and the carrier type changed from the p type to the n type, whereas the Sn valency remained constant at +2. These unconventional changes arose from the electronic separation corresponding to the Debye length, which is proportional to permittivity, and were attributed to weakened interactions between Sn 5s2 lone-pair electrons. Therefore, designing low-permittivity materials is beneficial for reducing the crystallite size required for stabilizing lone-pair states. These results are essential for designing emergent p-type oxides and improving their semiconducting properties and performance in transparent or high-power electronics.

Band Gap Narrowing by Suppressed Lone-Pair Activity of Bi3+

“…The orbital interactions in these materials can be described within the revised lone-pair model, which explains the asymmetric coordination environment of these cations in many crystal structures. − The metal s–anion p interactions create filled bonding and antibonding combinations as illustrated in Figure . The antibonding combination further interacts with the empty metal p orbitals.…”