Studies of dense electronic excitation induced modification in cobalt doped SnO2 thin films prepared by RF sputtering technique

Crystalline thin films of cobalt doped SnO2 undergoes modification by dense electronic excitation induced by Swift Heavy Ion (SHI) irradiation using 100 MeV Au8+ ion beam. Atomic Force Microscopy (AFM) and Power Spectral Density (PSD) analysis shows that the surface modification is dominated by diffusion of surface adatoms. Modification in surface features viz. grain size, rms roughness and roughness exponent can be controlled with homogeneity in surface features due to dense electronic excitation as observed from AFM-PSD and MFM analysis. X-ray diffraction results shows formation of new crystalline phase due to dense electronic excitation. The variation in strain along (101) and (110) crystal plane are nearly equal at irradiation fluence of 5 × 1012 ions/cm2 as calculated using X-ray diffraction results. UV-Visible studies shows formation of local energy states within the optical band gap region due to modification in electronic state of the system. The significant variation in Urbach's energy at irradiation fluence of 5 × 1012 ions/cm2 was observed. Transition in magnetic property after critical irradiation fluence of 5 × 1012 ions/cm2 with high coercivity and lowest saturated magnetization is observed. Resonance RBS studies shows Impurity free phase formation and amorphization causes reduction in density of the target due to amorphization. Very small modification in room temperature electrical conductivity was observed. Overall results shows that the modification in impurity free phase occurred by 100 MeV Au8+ ion irradiation in cobalt doped SnO2 thin films is tough to achieve by other techniques.