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Showing papers by "Debnarayan Jana published in 2007"


Journal ArticleDOI
TL;DR: In this paper, the structural and optical properties of mechanically milled high purity ZnO powder are investigated and a correlation between the structural properties of the powder and its optical properties is reported.
Abstract: The correlation between the structural and optical properties of mechanically milled high purity ZnO powder is reported in the present work. Reduction of average grain size and enhancement of strain as a result of milling have been estimated from the broadening of x-ray powder diffraction patterns. After milling, the optical bandgap, revealed from absorption spectroscopy, has been red-shifted and the width of the localized states, calculated from the analysis of the Urbach tail below the absorption edge, has been extended more and more into the bandgap. Moreover, the band tailing parameter is seen to vary exponentially with the inverse of the grain size. Finally, the positron annihilation technique has been employed to identify the nature of defects present (or generated due to milling) in the system and thereby to correlate the defect mediated modification of optical absorption in ZnO.

83 citations


Journal ArticleDOI
01 Jun 2007-Carbon
TL;DR: In this article, the optical properties of small radius single wall carbon nanotubes (SWCNTs) alloyed with boron were examined using relaxed C-C bond length ab initio calculations in the long wavelength limit.

40 citations