Changes in Structural and Optical Properties of TiO2 Thin Films Irradiated by Various Doses of 300 keV Carbon Ions.

TiO₂ thin films are synthesized by using DC magnetron sputtering system on Si (100) substrates and then annealed in a muffled furnace at 450 °C. Annealed samples are irradiated with carbon ions accelerated at the energy of 300 keV at various carbon ion doses of 4.2 × 10¹², 6.3 × 10¹³, 1.2 × 10¹⁴ and 2.5 × 10¹⁴ ions/cm². Structural and optical properties are studied by using different techniques such as x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, photo-luminescence spectroscopy and diffuse reflectance spectroscopy (DRS). The results show that structural and optical properties of the thin films modify with the amount of carbon ion doses. The synthesized thin film without ions irradiation has the rutile phase preferably, and by increasing the ion dose, it is changing into the anatase phase. Smaller crystallite size results in to the agglomeration process, and however, crystal size decreases with ion dose. PL spectra also confirm the formation of anatase phase from the rutile phase and different energy states due to the carbon ion implantation within the TiO₂ phase. The creation of energy states are linked with defects induced into the thin films and are required to improve the photocatalytic properties due to the hopping mechanism. DRS results show that bandgap of the pure TiO₂ thin film is 2.4 eV and it decreases to 2.1 eV by increasing the carbon ions dose. The achievement of this small band gap is attributed to the decrease in crystallite sizes and the defects induced by the ion implantation. [ABSTRACT FROM AUTHOR]