P. Dash

Structural evolution of TiO2 nanocrystalline thin films by thermal annealing and swift heavy ion irradiation

The present study probes into the transition from anatase to rutile phase of TiO2 in 100 nm thick nanocrystalline thin films under thermal annealing and swift heavy ion (SHI) irradiation. The films were prepared using sol-gel and spin coating techniques on silicon (100) substrates. The as-deposited films are found to be amorphous by glancing angle x-ray diffraction and Raman spectroscopy. Though thermal annealing is known to cause transformation from anatase to rutile phase of TiO2 in a temperature interval of 700–900 °C, in nanoparticle thin films, we found that a sizable volume fraction of anatase still remains even after annealing at 1000 °C. Irradiations by 200 MeV Ag ions on the other hand suppressed the anatase phase and almost phase pure rutile TiO2 could be obtained at a fluence of 3×1012 ions cm−2. A mechanism based on the competing effect of grain growth and conversion of anatase to rutile at the grain boundary of the anatase on annealing and conversion of anatase to rutile in the grains of the ...

Enhanced anomalous photo-absorption from TiO2 nanostructures

Two dimensional nanostructures have been created on the rutile TiO2 (110) surfaces via ion irradiation technique. Enhanced anomalous photo- absorption response is displayed, where nanostructures of 15 nm diameter with 0.5 nm height, and not the smaller nanostructures with larger surface area, delineate highest absorbance. Comprehensive investigations of oxygen vacancy states, on ion- irradiated surfaces, display a remarkable result that the number of vacancies saturates for higher fluences. A competition between the number of vacancy sites on the nanostructure in conjunction with its size is responsible for the observed anomalous photo-absorption.

Surface evolution of titanium oxide thin film with swift heavy ion irradiation

Modification of the surface morphologies of titanium oxide nanoparticle thin films under swift heavy ion (SHI) irradiation was investigated using glancing angle X-ray diffractometry and atomic force microscopy. Irradiation at low ion fluences leads to grain fragmentation and a narrowing of the grain size distribution, whereas grain growth with increased average grain size and grain size distribution occur at high fluences. Associated with the change in the grain size and size distribution there occurs topological modifications at different fluences of SHI irradiation. The SHI-induced grain fragmentation, grain growth and modification of surface topography are explained by the thermal spike model of ion–matter interaction.

Phase Transformation of TiO2 from Anatase to Rutile by Thermal Annealing and Swift Heavy Ion Irradiation

In the present study, we probe into the phase transition from anatase to rutile in nanocrystalline thin films under thermal annealing and swift heavy ion (SHI) irradiation. TiO2 thin films were prepared through chemical route using sol‐gel and spin coating techniques on silicon (100) substrates. The structural studies of the annealed films were characterized by GAXRD and Raman spectroscopy. Though thermal annealing is known to cause transformation from anatase to rutile phase of TiO2 in a temperature interval of 700 to 900 C, in nanoparticle thin films, we found ∼35 vol% of anatase still remains even after annealing at 1000 C. SHI irradiation by 200 MeV Ag ions on the other hand resulted in complete conversion to rutile phase at fluence of 3x1012 ions.cm−2. SHI induced thermal spike seems to be responsible for conversion of anatase to rutile phase.