Comparative Study of Ti- and Cu-Doped Zn2SnO4 Films Deposited by Spray Pyrolysis for UV Photodetection

This study aims to clarify how Ti and Cu doping differently influence the structural, morphological, electrical, and UV photodetection properties of Zn2SnO4 films prepared by spray pyrolysis. The comparison is based on the different chemical and electronic characteristics of the dopants and their resulting effects on charge transport and photoresponse. Zn2SnO4 films doped with 1–3 vol.% Ti or Cu were deposited under identical conditions and characterized using X-ray diffraction, atomic force microscopy, electrical measurements, and transient UV photoresponse at 365 nm. The results demonstrate distinct dopant-dependent structure–property relationships. Ti doping maintains a relatively homogeneous surface morphology and results in higher sheet resistance, whereas Cu doping produces stronger concentration-dependent morphological changes and lower sheet resistance at 1–2 vol.% Cu. The different electrical characteristics are reflected in the UV photodetection performance. The 1 vol.% Ti-doped film exhibits the highest responsivity of 239 mA/W, specific detectivity of 2.73 × 1010 Jones and a recovery time (τ90) of 74 ms, while the 3 vol.% Cu-doped film achieves the highest photo-to-dark current ratio of approximately 763 and a fast recovery time (τ90) of 70 ms. These results demonstrate that Ti and Cu provide different routes for tailoring Zn2SnO4 films for UV photodetection: Ti doping favors high responsivity and detectivity, whereas Cu doping enables efficient dark current suppression and rapid photoresponse. This study therefore establishes a direct relationship between dopant-dependent material properties and UV photodetector performance.