Mixed-Dimensional 1D ZnO-2D WSe2 van der Waals Heterojunction Device for Photosensors

2D layered van der Waals (vdW) atomic crystals are an emerging class of new materials that are receiving increasing attention owing to their unique properties. In particular, the dangling-bond-free surface of 2D materials enables integration of differently dimensioned materials into mixed-dimensional vdW heterostructures. Such mixed-dimensional heterostructures herald new opportunities for conducting fundamental nanoscience studies and developing nanoscale electronic/optoelectronic applications. This study presents a 1D ZnO nanowire (n-type)-2D WSe2 nanosheet (p-type) vdW heterojunction diode for photodetection and imaging process. After amorphous fluoro-polymer passivation, the ZnO-WSe2 diode shows superior performance with a much-enhanced rectification (ON/OFF) ratio of over 106 and an ideality factor of 3.4-3.6 due to the carbon-fluorine (C-F) dipole effect. This heterojunction device exhibits spectral photoresponses from ultraviolet (400 nm) to near infrared (950 nm). Furthermore, a prototype visible imager is demonstrated using the ZnO-WSe2 heterojunction diode as an imaging pixel. To the best of our knowledge, this is the first demonstration of an optoelectronic device based on a 1D-2D hybrid vdW heterojunction. This approach using a 1D ZnO-2D WSe2 heterojunction paves the way for the further development of electronic/optoelectronic applications using mixed-dimensional vdW heterostructures.