Improving the photoresponse of UV-Vis regions of multi-layered ZnO/NiO/Au photodetectors by controlling the number of laser pulses

Pulsed laser ablation in liquids (PLAL) using an Nd: YAG laser was employed to fabricate high-performance multilayer photodetectors from ZnO/NiO/Au. This study investigated the effect of pulse modulation of the ZnO specifically at 600, 700, and 800 pulses on the structural, morphological, and optoelectronic properties of the hybrid system, while maintaining constant concentrations of nickel oxide and gold. X-ray diffraction (XRD) analysis confirmed the presence of a pure-phase Wurtzite ZnO structure with a dominant (002) orientation, indicating a significant improvement in crystallinity as the pulse count increased. Morphological observations using atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM) revealed changes in surface topography, with sample C (800 pulses) exhibiting the highest film cohesion and a reduction in surface roughness to 9.7 nm. In summary, this material had remarkable photoelectric properties with the highest possible spectral response of 40 mA/W, photocurrent of 350 µA, EQE value of 7.5%, and the high specific sensitivity (D*) value of 1.35 × 10¹⁰ Jones. As such, the above enhancements were due to the effective interaction between the Au nanoparticle layer and the crystalline ZnO/NiO heterojunction, which lowered charge-carrier recombination and minimized dark current. Therefore, careful manipulation of pulse accumulation is an essential technique for creating superior photodetectors across the UV, visible, and infrared spectra.