Abstract:
Vertically aligned Zinc oxide nanorods (ZnO NRs) were successfully synthesized in this study using the sonochemical
method to improve the intrinsic properties of UV photodetector (PD). Three different thin films: Ti/Zn,
Ti/ZnO, and Ti/ZnO/Zn, with the thicknesses of 10 nm/55 nm, 10 nm/85 nm, and 10 nm/85 nm/55 nm respectively,
were deposited on glass substrates using the RF-sputtering technique. The synthesized ZnO NRs were
investigated using XRD, FESEM and Raman spectroscopy to determine the effect of Zn and ZnO as seed layers,
and ZnO as a buffer layer on the surface morphology, crystal structure, optical properties of ZnO NRs. The ZnO
NRs grown on Zn/Ti, ZnO/Ti, and Zn/ZnO/Ti are characterized by hexagonal crystal structure with preferential
growth in the c-axis direction. The ZnO NRs grown on Zn/ZnO/Ti displayed the highest density, uniform size
distribution, vertically aligned rods and aspect ratio. The UV device fabricated from the ZnO NRs grown on Zn
/ZnO/Ti also showed the highest photocurrent (360 μA) and responsivity of (878 mA/W). ZnO NRs grown on
Zn/ZnO/Ti were also observed to be highly stable and exhibited a relatively rapid response and recovery times
for different time intervals when exposed to the UV light of 365 nm wavelength. Thus, the inclusion of the ZnO
as a buffer layer (Zn as a seed layer/ZnO as buffer layer/Ti as a buffer layer) improve the properties of the ZnO
NRs. In addition, the current gain of ZnO NRs grown on Zn (55 nm)/ZnO (85 nm)/Ti (10 nm) – based ultraviolet
(UV) photodetector (PD) is about two times higher than that of conventional Zn (55 nm)/ZnO (85 nm)/Ti
(10 nm) thin-films UV PD, which is due to the higher surface-to-volume ratio of ZnO nanorods (NRs) compared
with their thin films. This study confirms the possibility of sonochemically fabricating vertically aligned ZnO
nanorods as well as its applicability as a viable UV photodetector
