Carbon ion irradiation induced structural, optical and electrical effects in TiO₂ nanoparticles

Carbon irradiation effects on spin coated TiO₂ nanoparticles (NPs), deposited on glass substrates, are studied for versatile applications. 5 MeV carbon ions with fluences, 1 × 10¹⁴, 5 × 10¹⁴, and 5 × 10¹⁵ ions/cm², are used to modify NPs. The ionization energy loss and defect production in the material as a result of impinging ions is estimated using Stopping and Range of Ions in Matter (SRIM). The modification in the base parameters is studied through various structural, optical, and electrical techniques. X-ray diffraction results before and after the irradiation depict the disturbance in crystal structure at lower ion fluence, which recovers at higher fluences giving an indication of dynamic annealing during irradiation process. Carbon irradiation also produces red shift, associated with the increasing grain size, as a function of ion fluence, which is observed through Raman spectroscopy. In addition, UV-visible spectroscopy shows the reduction in bandgap and four-point probe shows decrease in resistivity by increasing the carbon fluence. It is observed that the decreased resistivity and increased transmittance are linked with fluence rate, where the decrease in resistance is associated with hopping mechanism via defect compensation.