Surface trapping induced negative photoconductivity in Au nanoparticles functionalized SnO2/SnSe2 nanosheets under visible and NIR light

In this study, we report negative photoconductivity in SnO 2 /SnSe 2 nanosheets . We synthesized 2D n-type SnSe 2 nanosheets by the hydrothermal route and observed highly stable and repeatable negative photoconductivity (NPC) in the presence of both visible (532 nm) and near-infrared (NIR, 905 nm) irradiation. The existence of native SnO 2 skin on SnSe 2 nanosheets was confirmed with X-ray photoelectron spectroscopy (XPS). Negative photoresponse was improved significantly after Au nanoparticles (∼3.4 nm) functionalization of SnO 2 /SnSe 2 nanosheet. Au-SnO 2 /SnSe 2 exhibited responsivity/detectivity of 47.55 mA/W & 1.49 × 10 10 Jones and 47.8 mA/W &1.5 × 10 10 Jones at 10 V bias in visible and NIR light intensity of 50 µW/cm 2 , respectively, and quite a faster fall time of 841 µs and 791 µs in NIR exposure. The origin of NPC in SnSe 2 is attributed to the trapping of photogenerated hot carriers by surface adsorption of oxygen in ambient air. The NPC was further increased due to a significant increment of dark current (as well as I dark /I light ) after Au nanoparticles functionalization on SnO 2 /SnSe 2 .