Effect of La doping on key characteristics of SnO2 thin films facilely fabricated by spin coating technique

La-doped SnO2 thin films (1, 2.5, 5.0, 7.5 and 10%) have been coated on FTO substrates by a sol-gel spin coating technique. XRD studies confirms the (100) orientation of all prepared films of polycrystalline nature. Vibrational modes confirm the fabrication of single phase SnO2 films. EDX/SEM mapping confirms the presence of La in SnO2 films. AFM reveals the grain size in range of 17–82 nm along with RMS roughness in 13 and 38 nm. The direct band gap values of pure and La doped SnO2 thin films are varying between 4.15 and 3.95 eV. The refractive index (n) and absorption index (k) values were found to be reducing below 5% La doping and showed an increasing tendency beyond 5% doping. Further, the investigated values (χ1),(χ3) and n2 were found in the range of 0.032–47, 1.5 × 10−8 to 8 × 10−4 esu and 2.3 × 10−7 to 1.2 × 10−3, respectively.