Oxygen-doped ZnTe phosphors for synchrotron X-ray imaging detectors

Abstract

ZnTe:O powder phosphors were successfully prepared by a dry synthesis process using gaseous doping and etching media. It was found that dry doping by O 2 through ball-milling was an effective way to synthesize ZnTe:O powder phosphors and produced a red emission centered at 680 nm with a decay time of 1.1 ms. The emission intensity of dry O 2 -doped samples was three times more intense than from ZnO-doped samples, possibly due to a more uniform distribution of oxygen substitution on tellurium sites. The samples annealed in a 95% N 2 /5% H 2 forming gas atmosphere exhibited a x-ray luminescent efficiency five times higher than did powders annealed in vacuum or N 2 atmosphere. This enhancement was attributed to the removal of surface tellurium oxides. ZnTe:O phosphor screens were prepared with x-ray luminescence efficiencies equivalent to 56% of ZnSe:Cu,Ce,Cl and 76% of Gd 2 O 2 S:Tb screens under 17-keV radiation. An x-ray imaging resolution of 2.5 lines/mm was resolved, the same as that measured for commercial ZnSe:Cu,Ce,Cl and Gd 2 O 2 S:Tb screens. These results indicate that ZnTe:O is a promising phosphor candidate for synchrotron x-ray imaging applications.

Optical Characteristics of ZnTeO Thin Films Synthesized by Pulsed Laser Deposition and Molecular Beam Epitaxy

“…19 The spectral position of the optical transition near 1.8 eV observed in optical absorption and PL spectra for oxygen-doped samples is consistent with previously reported oxygen defects in ZnTe. 10,11,20,21 Since the maximum oxygen concentration in our sample is about 1 9 10 19 cm -3 , the optical transition in our samples is believed to result from oxygen pairs or oxygen cluster instead of the formation of an intermediate band alloy where a shift with oxygen concentration would be expected. The large absorption coefficient observed, however, is more consistent with a higher density of states than would be typically observed for a defect level transition.…”

“…7,8 This strong radiative transition in ZnTe:O has in fact been used in red light emission diodes, 9 and also a phosphorescent material for x-ray detectors, where long radiative lifetimes of >1 ls have been reported. 10 A higher oxygen content in ZnTe is predicted to introduce a narrow electronic band in the material, as explained by a band anticrossing model. 11 Experiments and calculations have suggested the presence of such an intermediate band in ZnTeO and the quaternary ZnMnTeO.…”

Raman scattering and photoluminescence of zinc telluride nanopowders at room temperature

“…As shown in the inset, the peak is centered at about 531.1 eV, which indicates that some oxygen atoms are incorporated into the ZnTe nanocrystals. If the ZnTe crystal surface is oxidized to form tellurium oxide, there should be two peaks associated to oxygen in the XPS spectrum, at which they locate at about 577 and 587.5 eV [15]. In addition, Ref.…”

Preparation and Optical Properties of Zn1-xMnxTe1-yOyHighly Mismatched Alloy

“…Though the band has the excitonic nature it is a very wide band, formed of numerous phonon replicas of the non-phonon line. At relatively high oxygen concentrations the non-phonon line is not visible at all [9] and only overlapping phonon replicas are present. This overall band is shifted with respect to the non-phonon line by ∆E = 0.09 eV.…”