In Situ I - V Measurements of an Ultraviolet Enhanced $\hbox{ZnS:TiO}_{2}/\hbox{n-Si}$ Quantum Dot Heterojunction Photodiode Under 120 MeV $\hbox{Au}^{9+}$ Ions

This paper reports the development of a $\hbox{ZnS:TiO}_{2}/\break \hbox{n-Si}$ heterojunction photodiode structure by deposition of colloidal $\hbox{ZnS:TiO}_{2}$ quantum dots (QDs) on the n-Si substrate. To study the diode performance under harsh radiation atmospheres, in situ dark $I$–$V$ characteristics of the $\hbox{ZnS:TiO}_{2}/\hbox{n-Si}$ photodiode have been studied under the irradiation of 120 MeV $\hbox{Au}^{9+}$ ions with an incremental increase in fluences from $\hbox{3} \times \hbox{10}^{11}$ to $\hbox{1} \times \hbox{10}^{13} \ \hbox{ions/cm}^{2}$. It shows the increase in rectification behavior with the increase in irradiation fluences caused by interface smoothening and interface defect annealing at higher fluences. X-ray diffraction patterns and TEM analysis also show the increased crystallinity of $ \hbox{ZnS:TiO}_{2}$ QDs of size approximately 2–5 nm, whereas photoluminescence spectra show the reduction of defects. These results are in support of the irradiation-induced effects in in situ $I$– $V$ measurements. The studies are also made for ultraviolet light of 376 nm wavelength (laser power 50 mW) and visible light of power 60 W for pristine and irradiated (at fluence $\hbox{1} \times \hbox{10}^{13} \ \hbox{ions/cm}^{2}$) $\hbox{ZnS:TiO}_{2}/\hbox{n-Si}$ heterojunction photodiodes.