Fabrication of V2O5/porous silicon heterostructures by simple and low-cost methods, morphological, structural, optical, and electrical characterization, and their first application as photodetectors

Abstract

This research presents the fabrication of heterostructures based on V₂O₅/porous silicon, their morphological, optical, structural, and electrical characterization, and their application as photodetectors. The fabrication of these heterostructures was performed in one step and with simple and low-cost methods compared to other more complex processes reported in the literature. The porous silicon layers were synthesized using the electrochemical anodization method and the V₂O₅ structures were obtained with the solvothermal or hydrothermal method, in this step the heterostructures were fabricated. The morphological characterization showed the formation of pores, these pores showed quasi-circular and irregular shapes, an average diameter of about 1.4 μm, and a pore length of around 22 μm perfectly aligned. The morphology of the V₂O₅ structures showed two morphologies a combination of concentric nanosheets and nanobelts with a thickness between 50 and 100 nm and a length greater than 10 μm for one sample and hollow microspheres with a diameter of about 5 μm for the second sample. The micro-Raman spectra demonstrated the formation of the orthorhombic V₂O₅ phase due to the Raman signals reported in the literature. X-ray diffraction corroborated the formation of the orthorhombic V₂O₅ phase, and it was possible to estimate the cell parameters and the size of the crystallites, which were found to be 31.5 and 16.4 nm. The optical characterization by photoluminescence showed main bands centered at 550 nm for the PS and 707 nm for the V₂O₅ structures. In addition, a passivation effect was observed after the deposition of the V₂O₅ structures on the porous silicon. Diffuse reflectance spectra together with the Kubelka-Munk method allowed us to estimate the optical bandgap which was 1.5 eV and about 2.1 eV for porous silicon and V₂O₅, respectively. Finally, electrical characterization under dark and illumination conditions showed rectifying and ohmic behaviors for the heterostructures, and a photocurrent effect was observed in the I-V curves. The photocurrent effect allowed the analysis of the I-t curves, which demonstrated the application of these heterostructures as the simplest photodetectors ever reported.