Structural, optical and photoelectric properties of Mn-doped ZnO films used for ultraviolet detectors.

Mn-doped ZnO (MZO) films were prepared on glass substrates using sol-gel dip-coating technology. The microstructural, morphological, optical and photoelectric properties of MZO films were investigated at different withdrawal speeds (WS: 20, 40, 60 and 80 mm s). The X-ray diffraction (XRD) patterns showed that all the films obtained were polycrystalline with a hexagonal structure, and the highest crystallinity of MZO films was observed as films were deposited at 40 mm s. The UV-Vis spectra revealed that the average optical transmittance of all samples was over 60% and the energy band gap of films decreased from 3.616 to 3.254 eV with the increase in withdrawal speed. The formed Au/MZO/Au photodetectors (PDs) indicate that a device prepared at 40 mm s shows superior properties both in response speed and detection capability, and the rise time is 1.871 s and fall time is 3.309 s at 365 nm for 3 V bias and the detectivity (*) reaches ∼1.7 × 10 Jones. Moreover, the responsivity of PDs is also affected by the distance between Au electrodes and external bias. This research provides a simple way to fabricate the UV PDs based on MZO films with faster response and higher detectivity.