Kamakhya Prakash Misra

Blueshift in optical band gap in nanocrystalline Zn1−xCaxO films deposited by sol-gel method

A blueshift in the optical band gap of nanocrystalline Zn1−xCaxO thin films has been obtained. A 12.72% enhancement in the band gap of ZnO thin films has been obtained using Ca dopant for the first time. The band gap widens from 3.38 to 3.81 eV as the Ca concentration increases from x=0 to x=0.15. The films are deposited by sol-gel method and have a hexagonal wurtzite phase with no indication of calcium. Grain size lies in the range of 12–92 nm. Atomic force micrographs indicate much smaller rms surface roughness showing significantly smooth surfaces.

Polarization Characteristics Variation of Visible Light on Reflection from ZnO Based Amorphous Films

The change in polarization characteristics of visible light reflected from amorphous ZnO and Ca doped ZnO thin films were studied. Highly transparent thin films of ZnO and Ca doped ZnO were deposited on glass substrate by sol–gel spin coating technique. Reflection studies revealed that the change in the polarization state and azimuth of the electric vector introduced by sample films are quite different as compared to those for reflected beam from uncoated substrate. The rotation of electric vector in reflected light was found to depend considerably on variation in angle of incidence as well as Ca concentration in ZnO. Films, interestingly, changed the incident plane polarized light to elliptically polarized on reflection.

Structural and morphological properties of Ce doped ZnO

Ce doped ZnO nanoparticles have been synthesized by sol-gel method and their structural properties, surface morphology and Fourier transform infrared spectra (FTIR) are studied. The XRD measurements indicate that the prepared nanoparticles have a hexagonal wurtzite structure of undoped ZnO and the presence CeO2 phase in doped ZnO samples. The calculated average crystallite size varies from 27 to 42 nm with increase in Ce concentrations. The absorption band observed 463 cm−1 is attributed to the ZnO stretching vibrations and EDX confirms the synthesis of undoped and Ce doped ZnO NPs.

Emission from Localized States in Co Doped BaTiO3 Films

Thin films of Ba(CoxTi1−x)O3 (0≤x≤0.06) are deposited by sol‐gel spin coating on fused quartz substrates. PL emission spectra are investigated in the present paper with excitation wavelengths near band gap and in visible region. PL emission is obtained in the green region for excitation wavelengths 477 and 488 nm whereas no emission is seen for band gap excitation wavelength. For both the wavelengths emission arising from localized states occur at 520 nm.

Substantial Enhancement in the Optical Band Gap of ZnO Films Using Ca Dopant

12.72% enhancement in the band gap of ZnO thin films has been obtained using Ca dopant for the first time. The films, deposited by sol-gel method, are nanocrystalline and highly transparent in the visible region.