成果報告書詳細
管理番号20110000001380
タイトル*平成22年度中間年報 希少金属代替材料開発プロジェクト 透明電極向けインジウム使用量低減技術開発
公開日2011/12/13
報告書年度2010 - 2010
委託先名国立大学法人東北大学 株式会社アルバック 三井金属鉱業株式会社 DOWAエレクトロニクス株式会社
プロジェクト番号P08023
部署名電子・材料・ナノテクノロジー部
和文要約和文要約等以下本編抜粋:研究開発項目(1)「スパッタリング法における透明電極向けインジウム使用量低減化技術開発」 【国立大学法人東北大学,株式会社アルバック,三井金属鉱業株式会社】(1)-1 新規ターゲット組成ならびにその大型ターゲット焼成技術の開発 ・新規ターゲット組成開発 【国立大学法人東北大学,三井金属鉱業株式会社,株式会社アルバック】 密度汎関数理論に基づく第一原理計算,LDA とLDA+U を,第4元素を含むITO に適用した.
計算結果は酸化状態(格子間酸素がある場合),還元状態(格子間酸素が無い場合)ともに,スズの置換サイトはdサイトではなく,bサイトであることを示していた.また、構造緩和に伴うSn原子周囲の原子変位量も実験値を再現し,硬X線光電子分光測定によって得られているITO の状態密度を再現できることを確認した.さらに,可視光から近赤外にかけての波長領域の光透過率計算も実施し,第4元素を添加しても高い透過度を有していることが明らかになった.図1に第4 元素としてアンチモンをドープした計算結果と文献値の比較を示す。
英文要約In order to reduce use of indium resources with 50% decrease, we are developing a novel ITO target with original composition (4th metal addition), innovative process adequate to this target, and mono-dispersed ITO nano-ink prepared by the novel synthesis method. DFT (density functional theory) and DFT+U (DFT with on-site Coulomb repulsion corrections) calculations show that the indium b-site is preferential site over d-site for tin atom substitution in indium oxide under both the oxidized and reduced conditions. Ti,Sb,Fe and Al are working as effective additive elements to reduce indium content in ITO films. Furthermore, DFT+U significantly modifies the electronic structure and consequently induce modifications in the calculated optical spectra of ITO. A new method was developed to achieve reducing indium content in ITO films. They were synthesized the following procedure : 1. Very thin(less than 10nm) normal ITO film(90% indium oxide) was sputtered on the glass sample at 523K. 2. New ITO film(50% indium oxide) was sputtered on a very thin normal ITO film at 523K. The performances on volume resistivity and transparency of the multi layer ITO film became better than those of normal ITO film(90% indium oxide). Highly-crystalline ITO nanoparticles with a cubic shape were successfully synthesized by way of a solvothermal system. Synthesis of the ITO nanoparticles was carried out by following procedure: A methanolic solution of indium and tin chlorides was poured into a same volume of a quaternary ammonium hydroxides solution in methanol under agitation at room temperature. The resulting solution was aged at 200 °C for 24 h in an autoclave. From XRD measurements, thus obtained solid products have an ITO crystal structure as a single-phase. TEM observation indicated that the ITO nanoparticle have cubic morphology with sharp edges, and the particle mean sizes were about 20 - 50 nm. ITO nano-inks, obtained by use of the ITO nanoparticles, showed high dispersibility and transparency in organic solvents. ITO thin-films with low haze and high transparency were also successfully preprared by use of the ITO nano-inks. Resistivity of the films was reached to 10-3 ohm /cm. Electric conductance of 3D percolation clusters is analyzed by means of random circuit approximation under a variety of particle size distributions. It should be also noted that this is the simplest method to realize a “correlated” version of percolation cluster. For example, when binary distributions of the size of conducting particles are introduced in a 3D problem, a significant change in the critical point and general conductance level was observed. Additionally, we investigated several theoretical approaches that can address the behavior of these modulated percolation models much more accurately than any previously proposed methods.
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