I. John Berlin

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.

Structural and optical characterisation of tin dioxide thin films by sol-gel dip coating technique

Tin oxide (SnO2) thin films were deposited on quartz substrates using sol-gel dip coating technique. X-ray diffraction (XRD) pattern indicated that the film annealed in air at 350°C was amorphous in nature, whereas, the films annealed in oxygen atmosphere at 350°C showed crystalline phase. The films were further annealed in oxygen atmosphere at 450°C and 550°C. All the diffraction peaks can be indexed to the tetragonal phase of SnO2 The surface morphology (SEM) showed that surface of all films were continuous and without micro cracks. The Energy dispersive X-ray spectroscopy (EDXS) spectra indicated an increase in the concentration of oxygen content with increase in annealing temperature. The energy band gap value for the film annealed in air was 3.88 eV. The optical band gap increased to 4.05 eV when annealed in O2 atmosphere. The photoluminescence (PL) spectra showed the presence of emission peaks in UV region and visible region of the electromagnetic spectra. Transparent oxide semiconductor SnO2 film finds potential application as an active channel layer for transparent thin film transistor.

Annealing effects on structural, electrical and optical properties of antimony-tinoxide thin films deposited by sol gel dip coating technique

Antimony-doped tin dioxide possess interesting physical and chemical properties. These properties have a wide range of applications such as catalysis and optoelectronic devices. In the present study, antimony-doped tin oxide (SnO2:Sb) thin films were deposited on the quartz substrates by sol-gel dip coating technique. The films were annealed at temperatures 350°C, 550°C and 850°C in air for 2 hours. The structure and surface morphologies were observed by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD patterns shows tetragonal structure for the SnO2:Sb films annealed at different temperatures. Crystallite size increased from 6 to 14 nm as annealing temperature increased from 350°C to 850°C. SEM studies reveals crack free and smooth surface for all the films. The grains are found to be homogenously distributed for films annealed at higher temperature. The electrical conductivity of the films annealed at 350°C and 550°C decreased and increased for the films annealed at 850°C. The optical...

Effect of annealing temperature on optical and electrical properties of ZrO2−SnO2 based nanocomposite thin films

ZrO2–SnO2 nanocomposite thin films were deposited onto quartz substrate by sol–gel dip-coating technique. Films were annealed at 500, 800 and 1,200 °C respectively. X-ray diffraction pattern showed a mixture of three phases: tetragonal ZrO2 and SnO2 and orthorhombic ZrSnO4. ZrSnO4 phase and grain size increased with annealing temperature. Fourier transform infra-red spectroscopy spectra indicated the reduction of –OH groups and increase in ZrO2–SnO2, by increasing the treatment temperature. Scanning electron microscopy observations showed nucleation and particle growth on the films. The electrical conductivity decreased with increase in annealing temperature. An average transmittance greater than 80 % (in UV–visible region) was observed for all the films. The optical constants of the films were calculated. A decrease in optical band gap from 4.79 to 4.59 eV was observed with increase in annealing temperature. Photoluminescence (PL) spectra revealed an emission peak at 424 nm which indicates the presence of oxygen vacancy in ZrSnO4. PL spectra of the films exhibited an increase in the emission intensity with increase in temperature which substantiates enhancement of ZrSnO4 phase and reduction in the non-radiative defects in the films. The nanocomposite modifies the structure of the individual metal oxides, accompanied by the crystallite size change and makes it ideal for gas sensor and optical applications.