Preparation of nanostructured FeS_2/Si heterojunction photodetector by laser ablation in water under effect of an external magnetic field

摘要

In the present work, the effect of applying an external magnetic field on the properties of one step laser-ablated iron pyrite FeS_2 nanoparticles (NPs) in water has been studied for the first time. The structural, optical properties and electrical properties of nanoparticles prepared without and with applying of magnetic field were investigated by using UV-Vis spec-troscopy, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, transmission electron microscopy, and Raman spectroscopy. X-ray diffraction studies show that the synthesized nanoparticles are pyrite FeS_2 with cubic structure and applying the magnetic field leads to increasing the intensity of XRD peaks without a change in the crystal structure. The optical energy gap increased from 2.35 eV to 2.75 eV when an external magnetic field was applied. Scanning electron microscopy investigations show that the synthesized FeS_2 NPs have a spherical shape and the average particle size of FeS_2 decreased from 30 to 14 nm when a magnetic field applied. The current-voltage properties of FeS_2NPs/p-Si heterojunction photodetector at dark and illumination were improved as the magnetic field applied. Applying the magnetic field of 3.5kOe enhances considerably the photosensitivity; the responsivity of the photodetector increases from 0.46 to 0.78 A/W at 350 nm.