Dopant Activation in Ta‐Doped SnO ₂ via Postdeposition Annealing for Transparent Electrodes

The scarcity and rising cost of indium drive the search for indium‐free transparent conducting oxides (TCOs). Ta‐doped SnO 2 (Ta:SnO 2 ) is a promising candidate due to its stable Ta 5+ state and resonant doping behavior. In this study, Ta:SnO 2 thin films are fabricated by pulsed laser deposition at room temperature, and the effects of deposition pressure (4–40 μbar), Ta doping concentration (2 and 7 wt% Ta 2 O 5 :SnO 2 targets), and ex situ annealing temperature (300°C–500°C) are systematically investigated. XPS and Hall effect analyses confirm that postdeposition annealing at ≥400°C effectively activates Ta 5+ dopants in films grown at low pressure (4–9 μbar), as evidenced by a concurrent increase in free carrier density despite the reduction of the surface‐adsorbed oxygen signature in XPS, suggesting vacancy annihilation and surface reoxidation. Successful dopant activation enables low resistivities, with an optimized resistivity of 1.9 × 10 −3 Ω cm achieved in films deposited using the 2 wt% target at 9 μbar and postannealed at 500°C, while maintaining >80% average visible to near‐infrared (vis–NIR) transmittance. While 500°C is not yet device‐compatible, this work motivates the exploration of postdeposition treatments that can locally crystallize and activate dopants in indium‐free TCOs without affecting the adjacent layers of the device.