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

Abstract

This paper reports the development of a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{ZnS:TiO}_{2}/\break \hbox{n-Si}$</tex></formula> heterojunction photodiode structure by deposition of colloidal <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{ZnS:TiO}_{2}$</tex></formula> quantum dots (QDs) on the n-Si substrate. To study the diode performance under harsh radiation atmospheres, in situ dark <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$I$</tex></formula> – <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V$</tex> </formula> characteristics of the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{ZnS:TiO}_{2}/\hbox{n-Si}$</tex></formula> photodiode have been studied under the irradiation of 120 MeV <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Au}^{9+}$ </tex></formula> ions with an incremental increase in fluences from <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{3} \times \hbox{10}^{11}$</tex></formula> to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{1} \times \hbox{10}^{13} \ \hbox{ions/cm}^{2}$</tex></formula> . 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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{ZnS:TiO}_{2}$</tex></formula> QDs of size approximately 2–5 nm, whereas photoluminescence spectra show the reduction of defects. These results are in support of the irradiation-induced effects in in situ <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$I$</tex></formula> – <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V$</tex></formula> measurements. The studies are also made for ultraviolet light of 376 nm wavelength (laser power 50 mW) and visible light of power 60 W for pristine and irradiated (at fluence <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{1} \times \hbox{10}^{13} \ \hbox{ions/cm}^{2}$</tex></formula> ) <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{ZnS:TiO}_{2}/\hbox{n-Si}$</tex></formula> heterojunction photodiodes.