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XRD and TEM study on microstructure of ITO

Tin doped indium oxide (ITO) is a transparent conductive oxide (TCO). Its electrical and optical properties are associated with its structure and microstructure as well with the preparation methods. Both, indium oxide In2O3 and ITO crystallize in a cubic bixbyite-type structure. A detailed structural study of ITO was reported recently. The aim of this work is to study the microstructural properties of ITO samples. Powder ITO samples with Sn doping level up to 12.3 at% were prepared by a sol-gel technique from InCl3 and SnCl4. The samples were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Diffraction lines were broadened. The line broadening increased with Sn content. Analysis of the line broadening was performed in the Rietveld structure refinement by the PANalytical X'Pert HighScore Plus program. Silicon powder was used as an instrumental standard. All the samples were nanocrystalline, crystallite sizes decreased and strain increased with the increase of tin content. Selected area electron diffraction (SAED) of doped samples showed that the observed regions were nanocrystalline having a bixbyite-type structure, giving strong evidence on ITO formation. TEM studies showed that grains had nearly spherical shape at lower tin doping level, while at higher doping level (>8 at% Sn) they appeared to be elongated. The crystallite sizes measured by TEM well agreed with those obtained by XRD line broadening analysis. High resolution transmission electron microscopy (HRTEM) gave an additional insight into the ITO microstructure.

indium tin oxide (ITO); microstructure; XRD; TEM

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