Interfacial band engineering in SnO2-coated ZnO nanowires for enhanced broadband photoresponse
Chinese Journal of Physics, cilt.104, ss.1055-1073, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 104
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.cjph.2026.10.029
- Dergi Adı: Chinese Journal of Physics
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, INSPEC, MathSciNet, zbMATH
- Sayfa Sayıları: ss.1055-1073
- Anahtar Kelimeler: Interfacial band engineering, SnO2/ZnO heterojunction, Ultraviolet photodetectors, Visible-blind photoresponse, ZnO nanowires
- Erzincan Binali Yıldırım Üniversitesi Adresli: Evet
Özet
Ultraviolet (UV) photodetectors have attracted significant attention for applications in environmental monitoring, flame detection, and optoelectronics. However, pristine ZnO nanowire (NW)-based devices are limited by high dark current and fast carrier recombination, which arise from oxygen vacancies and surface-related defects. Vertically aligned ZnO NW arrays were synthesized via thermal oxidation and surface-modified with SnO2 coatings by controlled hydrolysis at precursor concentrations of 5, 10, and 25 mM. Structural and chemical analyses (SEM, TEM, EDX, XRD, and XPS) confirmed concentration-dependent SnO2/ZnO heterojunctions with progressively improved interfacial continuity. Optical characterization revealed systematic photoluminescence quenching and only minor variation in the apparent optical-transition energy (∼3.22–3.23 eV), indicating that SnO2 modification does not produce a simple concentration-dependent band-gap-narrowing trend. The PL quenching is consistent with suppressed radiative recombination and improved interfacial carrier separation, although carrier lifetime was not directly measured. Electrical measurements under broadband xenon-lamp illumination across the UV, visible, and near-infrared regions (100 mW cm−2, −1 to +1 V bias) revealed a non-monotonic concentration-dependent variation in the integrated photoresponse, with the 25 mM sample exhibiting the highest net photocurrent. Transient current–time (I–t) measurements further demonstrated repeatable short-term light ON/OFF switching, with the rise and fall times decreasing from 5.0 and 10.0 s for pristine ZnO to 1.5 and 5.0 s for the optimized 25 mM device, respectively. The optimized 25 mM SnO2/ZnO device exhibited an effective broadband responsivity of 2.168 mA W−1 and an estimated broadband specific detectivity of 2.39×108 Jones, representing approximately 108-fold and 8.9-fold improvements, respectively, over pristine ZnO NWs under the same illumination conditions. The enhanced broadband response is consistent with the combined effects of the literature-based type-II interfacial configuration, surface-state passivation, and improved inter-nanowire carrier transport. These results demonstrate the beneficial effect of controlled SnO2-induced interfacial band engineering on the broadband photoresponse of ZnO NW devices. However, wavelength-resolved responsivity measurements are required to establish UV/visible selectivity or visible-blind operation.