Ultrahigh-gain single SnO2 nanowire photodetectors made with ferromagnetic nickel electrodes

Abstract

We report the first attempt at magnetic manipulation of the photoresponse in a one-dimensional device in which a highly sensitive ultraviolet photodetector, composed of tin dioxide nanowire (SnO2 NW) and ferromagnetic nickel (Ni) electrodes, has been fabricated and characterized. Surprisingly, as the Ni electrodes were magnetized, the photocurrent gain was greatly enhanced by up to 20 times, which is far beyond all of the previously reported enhancement factors for functionalized NW photodetectors. The underlying mechanism enabling the enhanced gain is attributed to both oxygen molecules adsorbed and surface band-bending effects due to the migration of electrons to the surface of SnO2 NW caused by the magnetic field of ferromagnetic electrodes. The novel approach presented here can provide a new route for the creation of highly efficient optoelectronic devices based on the coupling between ferromagnetic materials and nanostructured semiconductors. Yang-Fang Chen and co-workers from the National Taiwan University have dramatically enhanced the photoresponse of tin oxide semiconductor nanowires using a magnetic field. Tin oxide nanowires can produce a photocurrent under irradiation through the separation of electron–hole pairs at an irradiated location — an effect that makes the nanowires attractive components for a variety of devices including gas sensors and solar cells. The photoresponse depends on the nanowires' morphology, the presence of other ‘dopant’ species, and can be typically tuned through an electric field. The researchers have now devised a system in which the photocurrent can be amplified — by up to 20 times — using a magnetic field instead. A tin oxide nanowire is placed between two nickel ‘ferromagnetic’ electrodes and the resulting device subjected to a magnetic field. The high photoresponse observed is attributed to a migration of electrons towards the surface of the nanowires, induced by the electrodes' magnetization. This combination of nanowires with ferromagnetic materials may serve in future to fabricate efficient optoelectronic devices. We report the first attempt of magnetic manipulation of photoresponse in an one-dimensional device, in which a highly sensitive photodetector in the UV region composed of tin oxide nanowire and ferromagnetic nickel electrodes have been fabricated and characterized. Surprisingly, as the Nickel electrodes were magnetized, the photocurrent gain can be greatly enhanced by up to 20 times. The underlying mechanism is attributed to both oxygen molecules adsorbed and surface band bending effects due to the migration of electrons to the surface of tin oxide nanowire caused by the magnetic field of ferromagnetic electrodes.