P.V. Thomas

Band gap tuning and improved optical properties of ZrO2-SnO2 nanocomposite thin films prepared by sol-gel route

Transparent nanocomposite ZrO2-SnO2 thin films (0.1/0.9 (ZS19), 0.5/0.5 (ZS55) and 0.9/0.1 (ZS91) of ZrO2/SnO2 were prepared by sol-gel dip-coating technique. X-ray diffraction (XRD) pattern of ZS55 shows a mixture of three phases: tetragonal ZrO2 and SnO2 with the crystal sizes of 11 nm and 8 nm, respectively and orthorhombic ZrSnO4 with the crystal size of 14 nm. Scanning electron microscopy (SEM) observations show that microstructure of ZS55 consists of isolated SnO2 particles dispersed in ZrO2 matrix. An average transmittance greater than 85% (in UV–visible region) is observed in ZS55 thin film. The band gap of the nanocomposite thin film decreases from 5.33 to 4.24eV with increase in Sn concentration which can be directly employed in extending the range of tunability of the band gap. Photoluminescence (PL) spectra reveal an intense emission peak at 426nm in ZS55 sample which indicate the presence of oxygen vacancies in ZrSnO4.