Swift heavy ion irradiation induced modifications on the structure, optical and electrical properties of pulsed laser deposited anatase TiO₂ thin films

The swift heavy ions of Ag⁷⁺ (100 MeV) were used to irradiate the anatase TiO₂ thin films prepared by pulsed laser deposition (PLD) technique on quartz substrates. The effect of ion fluences (1×10¹², 1×10¹³ and 1×10¹⁴ ions/cm²) on the structure, surface morphology, optical and electrical properties are investigated through several analytical techniques such as XRD, Micro-Raman, FTIR, XPS, AFM, FESEM, UV–visible and Hall measurements. The analysis of XRD data shows a gradual shift in the (101) plane toward higher diffraction angle on increasing the ion fluence which increases the lattice strain in the films. The EDS spectra reveal a modest Ti-rich composition with a significant shift following irradiation for both as-grown and irradiated films. The development of hillocks at increased ion fluence and considerable grain splitting following irradiation are observed in SEM micrographs. AFM images exhibit increase in surface roughness with the increase in ion fluence. Moreover, there is a significant drop in the band gap of the irradiated thin films from 3.92 to 3.44 eV with the increase in ion fluence. The various electrical parameters such as carrier concentrations (n), Hall mobility (μ), electrical resistivity (ρ), Hall coefficient (R_H), etc., are determined by the Hall measurements at room temperature. This study indicates that the SHI irradiation plays a significant role in tunning the physical properties of anatase TiO₂ thin films.