Investigation of optical properties of SnO2 nanoparticles

The preparation of SnO2 nanoparticles with size below 5 nm is achieved using an inexpensive method. The study of structural properties is done by XRD, TEM and FTIR, while the optical properties are observed using UV–Visible and photoluminescence spectroscopy. The prepared SnO2 nanoparticles are annealed at low (200 °C), medium (600 °C) and high (1000 °C) temperature. The UV–Visible spectroscopy shows an interesting band type absorption for high temperature annealed sample. The oxygen vacancies play vital role in the optical properties. These vacancies are the cause of abnormal absorption in high temperature annealed SnO2 nanoparticles. The Urbach energy of all the SnO2 nanoparticles annealed at 200, 600 and 1000 °C is also calculated. A high value of Urbach energy for SnO2 nanoparticles annealed at 1000 °C is found. The band gap of SnO2 annealed at 1000 °C is found to be higher than SnO2 annealed at 200 and 600 °C, which has been explained on the basis of Burstein–Moss shift. The concentration of charge carrier is calculated using Hall effect and found to be increasing as the annealing temperature increases.