Optimizing the properties of In–N dual-doped SnO2 films: incorporation of nitrogen into the SnO2 lattice at the optimal content via direct current sputtering

Direct current magnetron sputtering was employed to fabricate In–N dual-doped SnO₂ films, with varying concentrations of N₂ in a mixed sputtering gas of N₂ and argon (Ar). The quantity of N-substituted O elements in the SnO₂ lattice was confirmed through energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). A comprehensive investigation of properties of the In–N dual-doped SnO₂ films was conducted using various techniques, including X-ray diffraction analysis, field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), ultraviolet absorption spectroscopy, Hall effect measurements, and current–voltage (I–V) characteristic assessments. The results indicated that when the ratio of N₂ to the mixed gas (Ar + N₂) exceeded 15%, the films exhibited p-type conductivity. The films demonstrated optimal electrical and structural properties at an N₂ content of 45%, with a resistivity of 5.1 × 10⁻³ Ω cm, hole mobility of 12.75 cm² V⁻¹ s⁻¹, crystal grain size of 25.74 nm, and a root mean square (RMS) roughness of 0.61 nm, resulting in the highest photocurrent at the INTO-45/Si interface.