Plasmonic Gold Nanoparticle-Decorated Ultrathin SnO2 Nanosheets with Superior Ultraviolet and Visible Photoresponsivity

Ultrathin transparent semiconducting oxides have attracted considerable attention in multifunctional electronic and optoelectronic devices, owing to their exciting physical properties and excellent stability. However, due to their wide bandgap, absorption in the visible region is very limited. Here, we show enhanced light–matter interactions by integrating plasmonic gold nanoparticles onto ultrathin SnO2 nanosheets, leading to higher optical absorption in the visible spectra. In this work, a vacuum-free liquid metal printing technique is used to deposit large-area ∼1.9 nm thick SnO2 nanosheets, which were then decorated with gold nanoparticles by utilizing an electrostatic self-assembly technique. The enhancement of the electric field due to localized surface plasmon resonance and plasmon-induced hot electron generation at the Au–SnO2 interface is verified utilizing COMSOL simulations. Moreover, experimental observations of fabricated photodetectors based on the Au–SnO2 hybrid structure demonstrate a broadband spectral response ranging from ultraviolet to visible wavelengths. In particular, we observe an improved room temperature photoresponsivity of ∼950 mA W–1 and a 17-fold enhancement in photocurrent at a 400 nm wavelength as compared to bare SnO2. This work provides a viable route to tune the optical properties of wide bandgap 2D functional oxides, making them attractive for large-area nanoscale broadband photodetectors and optoelectronic devices.