Effects of microstructure on the optical properties of tin-doped indium oxide thin films studied by electron energy loss spectroscopy

We have studied thin films of tin-doped indium oxide prepared by e-beam evaporation using a zone-confining arrangement and exhibiting different microstructures. Specimens prepared with 5.1 at% tin are polycrystalline in nature while those prepared with 6.6 at% tin exhibit a granular microstructure which consists of a mixture of amorphous and crystalline grains. The appearance of the amorphous phase is attributed to the segregation of impurities. Three peaks at energies of 6, 9 and 14 eV are observed on the extinction coefficient of these specimens. These peaks become much sharper for the specimen showing a mixed microstructure due to improved crystallinity and purity of crystalline grains in this specimen.