Enhanced Photocurrent and Dynamic Response in Vertically Aligned In<sub>2</sub>S<sub>3</sub>/Ag Core/Shell Nanorod Array Photoconductive Devices

Enhanced photocurrent values were achieved through a semiconductor-core/metal-shell nanorod array photoconductive device geometry. Vertically aligned indium sulfide (In<sub>2</sub>S<sub>3</sub>) nanorods were formed as the core by using glancing angle deposition technique (GLAD). A thin silver (Ag) layer is conformally coated around nanorods as the metallic shell through a high pressure sputter deposition method. This was followed by capping the nanorods with a metallic blanket layer of Ag film by utilizing a new small angle deposition technique combined with GLAD. Radial interface that was formed by the core/shell geometry provided an efficient charge carrier collection by shortening carrier transit times, which led to a superior photocurrent and gain. Thin metal shells around nanorods acted as a passivation layer to decrease surface states that cause prolonged carrier lifetimes and slow recovery of the photocurrent in nanorods. A combination of efficient carrier collection with surface passivation resulted in enhanced photocurrent and dynamic response at the same time in one device structure. In<sub>2</sub>S<sub>3</sub> nanorod devices without the metal shell and with relatively thicker metal shell were also fabricated and characterized for comparison. In<sub>2</sub>S<sub>3</sub> nanorods with thin metal shell showed the highest photosensitivity (photocurrent/dark current) response compared to two other designs. Microstructural, morphological, and electronic properties of the core/shell nanorods were used to explain the results observed.