Band gap tailoring and photosensitivity study of Al-doped SnO₂ nanocrystallites prepared by sol–gel technique

Electrical, optical and photosensitivity of aluminium-doped tin oxide (Al-SnO₂) nanocrystallites prepared by sol–gel technique and annealed at 400 °C and 500 °C are studied. The synthesized nanocrystallites are characterized using spectroscopic techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX) and UV–VIS-DRS spectroscopy. The PXRD data confirm the development of polycrystalline nanocrystallites having crystal size ≈ 6.8 nm at 400 °C which increases to ≈ 8.7 nm on annealing at 500 °C. SEM images illustrate the formation of nanoclusters. Broad characteristics bands of FTIR spectra demonstrate the presence of physical interaction between SnO₂ and Al₂O₃. EDX spectra illustrate the presence of aluminium, tin and oxygen in the particles annealed at 400 °C and 500 °C with composition Sn_0.726Al_0.274O₂ and Sn_0.809Al_0.191O₂, respectively. UV–VIS-DRS spectroscopy illustrates that the band gap energy of 400 °C and 500 °C annealed materials are 3.42 and 3.35 eV, respectively. First time, the electrical properties and photosensitivity of the Al-SnO₂ nanocrystallites annealed at two different temperatures are studied by making the particles into thin films of thickness 103µ (400 °C) and 106µ (500 °C) on glass substrate.