The effect of different substrate-inclined angles on the characteristic properties of ZnO nanorods for UV photodetectors applications

The effect of six different substrate-inclined angle with the vessel on the characteristics properties of the Zinc Oxide (ZnO) nanorods was explored and reported. The vertically well-aligned ZnO Nanorods (NRs) were synthesized on glass substrates by using the low-cost chemical bath deposition (CBD) method at 90 °C. The RF magnetron sputtering has been employed to deposit the ZnO nanoseed layer on glass substrates and electrodes for UV photodetectors (PDs) devices. The morphological, structural, and optical properties of the synthesized ZnO NRs have been investigated using various characterization techniques for different substrate- inclined angles. Also, the high-quality UV photodetector-based ZnO NRs have been fabricated for the optimum substrate-inclined angle of 70° with the vessel by applying a different bias voltage. The results found that variation of substrate-inclined angles have the remarkable and significant effect on the shape, size, length, alignment, density distribution, structure, lattice parameters, crystalline size, energy band gap (E_g), and optical properties of ZnO NRs. The average diameters and length of grown ZnO NRs were in the range of (58–249) nm and (303–2518) nm, respectively. The high aspect ratio, length, and growth rate were observed for ZnO nanorods grown at 70° substrate-inclined angle. The preferred orientation of ZnO NRs was along (002) hexagonal wurtzite plane and the intensity of (002) diffraction peak for ZnO NRs was increased with increasing substrate-inclined angles. The average crystalline size was in range of (46.7–58.8) nm. The average transmittance of ZnO NRs showed a reduction in the range of (44.5–3.3)% as the substrate angle increased. The optical studies show that the synthesized ZnO NRs have the direct E_g in the range of (3.16–3.254) eV. The fabricated UV PD-based ZnO NRs showed high performance and quality. The different bias voltage study shows that the ZnO nanorod UV PD has higher stability and repeatability at 5 V bias voltage. The PDs device exhibited the responsivity value of 3.49903 A/W to 390 nm light wavelength at 5 V, which is higher than those reported for UV PDs-based ZnO NRs. At 5 V bias voltages, the fabricated UV PDs showed a faster response and recovery times of 0.3402 S and 0.1639 S, respectively.