Growth of Au capped GeO₂ nanowires for visible-light photodetection

A single step process to grow Au capped oxygen deficient GeO₂ crystalline nanowires via generation of growth species through the metal induced surface decomposition of Ge substrate is reported. Without the external source supply, the growth of the Au-GeO₂ nanowires on the Ge substrate is addressed with possible mechanism. Despite high band gap, application of GeO₂ as a possible new material for visible light photodetection is presented. The as-grown samples were found to have a photo-response of ≥10² with 17% external quantum efficiency at -2.0 V applied bias upon visible-light illumination (λ = 540 nm, 0.2 mW/cm²). This visible-light detection can be attributed to the oxygen vacancy related defect states as well as localized surface plasmon resonance induced absorption and subsequent hot electron injection from Au to conduction band of GeO₂. The photodetection performance of the devices has been understood by the proposed energy band diagrams. In addition, 4 times enhancement in the efficiency has been achieved by further decoration of the Au nanoparticles on the as-grown nanowire surfaces.