Effect of 200 MeV Ag15+ ion beam irradiation at different fluences on WO3 thin films

Abstract

The physical properties of thin films can be modified by swift heavy ion (SHI) beam irradiation of the target material. Spray-deposited tungsten trioxide (WO3) thin films of thickness 89 nm were irradiated with 200 MeV Ag15+ ion beam at various fluences of 5 × 1011, 1 × 1012, 5 × 1012, and 1 × 1013 ions/cm2. The X-ray diffraction pattern of the pristine film was orthorhombic, while the irradiated film became amorphous at different fluences except for 5 × 1012 ions/cm2; this may be due to the re-crystallization effect induced by irradiation. The observed Raman modes for the pristine film were in good agreement with those reported for the irradiated WO3 films. The intensity of Raman peaks decreased upto 5 × 1012 ions/cm2 and vanished completely at further higher fluences. The optical transparency of the pristine film was much higher than that of irradiated ones. Both the direct and indirect band gaps showed a red shift. AFM data revealed significant surface modifications after irradiation. Transport properties were also studied for both the pristine and irradiated films by the Hall effect. A decrease in resistivity was observed with the increase in fluence. These results are discussed in this paper.