Preparation and Characterization of In2O3 : Lix(x=0−1.0)

Ryuta KIYOSHIMA, Shigemi KOHIKI*, Shigenori MATSUSHIMA and Masaoki OKU††

Department of Materials Science, Faculty of Engineering, Kyusyu Institute of Technology;Tobata-ku, Kita-kyusyu-shi 804-8550 Japan
Kitakyusyu National College of Technology; Kokuraminami-ku, Kita-kyusyu-shi 803-0985 Japan
†† Institute for Material Reserch, Tohoku University; Aoba-ku, Sendai-shi 980-8577 Japan

Lithium-doped indium oxide crystals (In2O3 : Lix, x=0−1.0) were synthesized by calcination in flowing oxygen of dried powders from aqueous solutions of InCl3 with Li. Only the peaks from cubic In2O3 crystal were observed in X-ray diffraction (XD). The lattice constant increased from 10.116 to 10.163 A, and the optical absorption energy decreased from 2.72 to 2.68 eV with increasing x in In2O3 : Lix. The lattice constant estimated by XD and the optical absorption edge in UV-visible absorption spectrometry remained at constants (10.163 A and 2.68 eV) in the region of x=0.5−1.0. Tight-binding (TB) band-structure calculations were performed for studying changes in the electronic structure with Li doping. The calculated energy splitting between the top of the valence band and the bottom of the conduction band decreased by Li doping at the empty sites (8a and 16c) of pure In2O3 crystal, which was consistent with the experimental decrements of the absorption energy with x in In2O3 : Lix. Changes in the valence band spectra by X-ray photoelectron spectroscopy of the In2O3 : Lix(x=0, 0.2 and 1.0) agree with that in the density of states by the TB calculation for two Li atoms doped at 8a or at 16c sites of In2O3 crystal. Doping of Li atoms into the interstitial sites affects both on the valence band and the conduction band minimum of the In2O3 crystal.

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