Sustainable Doping via Molecular Adsorption on Thin-Film Semiconductor Bi ₂ O ₂ Se

Doping in semiconductors is commonly achieved by incorporating foreign atoms into the crystal, which is a complex process that requires precise control. In two-dimensional or thin-film semiconductors, an alternative approach involving surface modification, such as molecular adsorption, has been proposed and attempted. However, successful doping via gas adsorption has not yet been reported. In this work, we present both first-principles calculations and experimental evidence demonstrating the feasibility of this approach in thin-film semiconductor Bi₂O₂Se, which has recently gained attention for its high carrier mobility, moderate band gap, and excellent air stability. We find that p-type doping can be achieved through surface adsorption of molecules such as NO₂, which exhibits stable chemisorption and significant charge transfer. This adsorption-induced p-doping effect significantly modulates the threshold voltage in as-grown n-type samples and remains stable for more than 10 days under ambient conditions, markedly improving electrostatic control and switching behavior in Bi₂O₂Se-based devices.