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Le Tellurure de Cadmium amorphe oxygéné a - CdTe:O Synthèse et étude de quelques propriétés physico-chimiques

Youssef El Azhari 1
1 Semiconducteurs II-VI
LPSCM - Laboratoire de physique des solides et des couches minces
Abstract : The work presented in this thesis is part of the study of the properties of thin layers of semiconductor materials based on cadmium telluride CdTe. The study of the influence of various deposition parameters on the properties of CdTe thin films has enabled us to develop a method of preparing a new material based on CdTe. It is the oxygenated amorphous cadmium telluride aCddTe: O. The thin film deposition of CdTe a-O from a target polycrystalline CdTe requires the use of a plasma high oxidizing power. Plasma we used is obtained from a mixture of argon Ar, oxygen and nitrous subjected to an electric field radio frequency of 13.56 MHz. We have shown that dinitrogen plays a catalytic role in the oxidation of CdTe deposition in the plasma which determines the composition of thin films of a-CdTe: O Indeed, the oxygen content of these layers can be around 60% when the oxidation conditions are pushed to the extreme. The optical properties of thin layers of a-CdTe: O highly dependent on the oxygen content of the layers. Thus the energy of the optical gap Eg varies between 1.45 eV and 1.85 eV for an oxygen content between 0 and 40 atomic%. The extrapolated value of the infrared the refractive index of these layers varies, in turn, between 2.15 and 2.75. The XPS study shows that the oxygen incorporated in the films of a-CdTe: O binds to both tellurium atoms as those of cadmium. Using X-ray reflectometry, we have highlighted the influence of plasma oxidation on previous thin CdTe. We have thus succeeded in developing a method that can significantly reduce the surface roughness of thin layers of CdTe. When pushed to the extreme oxidation conditions, we can obtain the amorphous thin stable oxide CdTeO3. The study of electrical properties of these layers can highlight their insulating nature. We were able to determine their electrical resistivity continues 3x10 ^ 6 ohm.m and relative dielectric constant (16). The optical transmission measurements were used to determine their optical gap energy Eg = 3.91 eV and the extrapolated value of their infrared refractive index (1.90). Thin layers of amorphous CdTeO3 were also deposited on CdTe thin film. Appropriate annealing structures obtained can grow CdTeO3 of polycrystalline CdTe polycrystalline.
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Youssef El Azhari. Le Tellurure de Cadmium amorphe oxygéné a - CdTe:O Synthèse et étude de quelques propriétés physico-chimiques. Autre [cond-mat.other]. Université Cadi Ayyad, 2003. Français. ⟨tel-00789199⟩

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