铟锡氧化物电子结构和光学性质的第一性原理研究

THE ELECTRONIC STRUCTURE AND OPTICAL PROPERTIES OF INDIUM TIN OXIDE: THE FIRST-PRINCIPLES CALCALTION STUDY

透明导电氧化物薄膜具有高的可见光透明度和较低的电阻系数,已成为当前的研究热点.早期关于氧化铟材料的理论研究没有考虑In原子4d电子的交换关联库伦位能,使得计算的带隙值远低于实验值;另外关于Sn原子掺杂的氧化铟物理特性的研究比较少,不同掺杂位置对材料结构和电子结构的影响缺乏系统的研究.本文采用基于密度泛函理论的第一性原理的LDA+U方法系统研究了Sn掺杂In_2O_3材料的电子结构和光学性质.研究表明Sn的引入能降低In_2O_3体系的禁带宽度,并在禁带中引入主要由Sn-5p轨道上的电子构成的杂质能级,禁带宽度的降低和杂质能级的引入可以改变In_2O_3材料对可见光的透明度,并可提高其电导率.Sn离子掺杂后体系的几何结构和电子结构发生改变是导致体系一系列性质发生改变的原因.通过Mulliken布局分析得知掺杂后的Sn-O键相比于掺杂前的In-O键的键长变短,同时前者比后者的离子键成份更强.

Transparent conducting oxide thin film with high visible light transparency and low resistivity, has been an attractive research focus. However, the early theoretical study underestimated band-gap of In2O3 because of the lack of considering the exchange-correlation potential about In-4d. Moreover, few researches focus on physical properties of Sn doped In2O3, and there is little systematic study about the effect of doped configuration on the electronic structures. In this paper, the electronic structure and optical properties of Sn doped In2O3 are researched systemically by the first-principles calculation based on the density functional theory with the LDA＋U method. It is found that the doped Sn makes the band-gap of In2O3 narrower, and introduces impurity level which mainly includes the Sn-5p. The narrower band-gap and the impurity level can enhance the In2O3 transparency to visible light, and improve the conductivity. The changed crystal and electronic structures of Sn doped system lead to the varying properties. According to the Mulliken distribution analysis, Sn-O bond is shorter than the In-O bond in the undoped system, and the intensity of the ionic bonding of Sn-O is stronger than that of In-O.