Ion implantation-driven defect engineering in BiVO4 thin films for catalytic applications

Designing and controlling structural defects in semiconductor photocatalysts using ion implantation remains a challenging issue. This work explores the evolution of point and complex defects in 100 keV P+-implanted BiVO4 thin films using slow-positron beam (SPB) measurements combined with theoretical calculations. Variable-energy (0.1–14 keV) Doppler broadening (VEDB) and electron momentum distribution (VEEMD) analyses, together with two-component density functional theory (TC-DFT) calculations, are employed to characterize defect evolution. Complementary techniques, including SRIM simulations, Rutherford backscattering spectrometry (RBS), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy, are used to further assess the defective structures. The results indicate that a competitive formation of point defects occurs in P+-implanted BiVO4 thin films, including oxygen, bismuth, and vanadium vacancies (VO, VBi, and VV), oxygen substitution by phosphorus (PO), along with more complex defects such as VBi + PO and VV + PO. The evolution of those defects proceeds differently across different depth regions (0–30, 30–117, and 117–225 nm) and at different implanted fluences (1013–1015 ions.cm−2) in the BiVO4 thin film. Comprehensive analyses using SPB, photoluminescence (PL), and ultraviolet–visible (UV–Vis) techniques together with DFT calculations reveal that P+-induced VO, VBi, and VBi + PO defects positively modulate the electronic structure and optical properties of BiVO4 thin films, thereby offering a promising strategy to improve their photocatalytic performance. This study provides new insights into defect engineering and control in thin-film materials via ion implantation.