Abstract
Pure and Gd-doped nano-crystalline GeSe 2 were prepared by the melt-quenching technique. The crystal structure, local structure and emission properties are investigated. Structure analysis using Rietveld program suggests monoclinic structure for both virgin and doped samples with nano-particle size 41nm for GeSe 2 and 48nm for Gd-doped sample. A wide optical band gap as estimated from absorbance measurements is 4.1ev and 4.8ev for pure and doped samples in accordance with the confinement effects. Raman spectra show two unresolved components at ~ 202 cm-1 with broad line width. Also, well identified low intensity (υ -1 ) and high intensity (υ > 250 cm -1 ) bands are detected. For Gd-doped sample, the main band is shifted to lower energies and its FWHM is reduced by ~ 50% accompanied by an intensity increase of about ~ 17 fold times. The photoluminescence analysis of the pure sample shows a main emission band at ~ 604 nm. This band is splitted into two separated bands with higher intensity. The detected emission bands at wavelength > 650 nm are assigned to transmission from 6 G J to the different 6 P J terms.
Highlights
Chalcogenides based Ge-Selenides have significant infrared (IR) transparency in the wavelength region between ~1 and 12μm which makes them suitable for passive IR optics, for example as optical fibers, wave guides, sensors, nano-lens and photo-resist materials for the micro and nano fabrication [1,2,3,4,5,6]
The search-match program showed no diffraction lines related to the elements or their oxides; only one phase of GeSe2 was present according to the ICDD card number (71-0117)with the monoclinic space group P21/c
During Rietveld analysis, a preferred orientation along the [0 0 l] direction was detected. The latter could not be avoided during measurements in spite of back-loading and fine grinding of samples
Summary
First Investigation of Optical Properties and Local Structure of Gd3+ Doped Nano-Crystalline GeSe2 as x-ray phosphors [22,23,24]. Gd3+ activated phosphors have attracted much attention for their well defined emission in the ultraviolet region [14, 26, 27]. All Raman and PL investigations have been performed for Ge-Se system in the glassy and crystalline states. In this work we present new diagnostic Raman and PL data on nanocrystalline GeSe2 and GeSe2:Gd. From absorbance measurements a wide optical band gap of 4.8 for the doped sample is reported. New Raman activities and PL emission bands were recorded for virgin and Gd-doped samples over the visible range. The main objective for the present work is the development of visible source based on the radiative transition of Gd3+ in nano-crystalline GeSe2
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