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Electronic characteristics of Metal/Insulator Super-lattice, based on the first principle electronic structure calculation

基于第一原理电子结构计算的金属/绝缘体超晶格的电子特性

基本信息

批准号：
13640333
负责人：
MATSUURA Mitsuru
金额：
$ 1.92万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640333/
关键词：
Metal Insulator Superlattice FLAPW method density functional theory band offset tunneling current Xray phoyoelectron spectroscopy (XPS)FLAPW 状態密度光電子分光

项目摘要

Based on the density functional theory and the FLAPW method, the first principle electronic structure calculation has been performed for the metal Ti/Insulator MgO Superlattice.At first, atomic configuration in the superlattice interface is determined from the comparison of calculated total energies. The calculated result shows that Ti atom is in contact with the 0 atom at the interface. Based on this atomic configuration at the interface, electronic band structure of the superlattice is calculated. It is found that there are two kinds of electronic states.One is the states, which exist mainly in only the Ti or MgO layer and receive the quantum confinement effects (quasi-two dimensional electronic states). Another is the states which exist in the both Ti and MgO layers and have the finite dispersion for energy. Also there are metallic states in a Ti layer within the band gap in an insulator MgO layer and then the metallic states constitute the quasi two-dimensional electronic states in a metallic Ti layer.Based on the electronic structure and the experimental band gap in MgO, band diagram of Ti/MgO superlattices, which shows the relative position of the conduction and valence electronic states in Ti and MgO layers is obtained.Also, calculated electronic band structure is used to calculate a tunneling current, i.e., a tunneling of an electron between two metallic Ti layers through the thin MgO layer under an electric field.Xray photoelectron spectra (XPS) has been measured in the metal Ti/insulator MgO superlattice and has been discussed in relation to the valence band density of states. Two spectra before etching and after 5-minutes etching show the difference, which reflect the electronic states in MgO layer and Ti layer, being in good agreement of the theoretical density of the state. This XPS experiment is considered to show the reliability of our theoretical electronic structure calculation.

基于密度泛函理论和FLAPW方法，对金属钛/绝缘体氧化镁超晶格进行了第一性原理电子结构计算，首先通过计算总能量的比较确定了超晶格界面的原子构型。计算结果表明，钛原子在界面上与0原子接触。根据界面原子构型，计算了超晶格的电子能带结构。发现存在两种电子态，一种是主要存在于钛层或氧化镁层中，受量子限制效应的电子态(准二维电子态)。另一种是同时存在于钛层和氧化镁层中的能量色散有限的态。此外，在绝缘层中的带隙内，钛层中还存在金属态，这些金属态构成了金属钛层中的准二维电子态。根据金属氧化镁的电子结构和实验带隙，得到了钛/氧化镁超晶格的能带图，它显示了导电态和价电子态在钛层和氧化镁层中的相对位置。同时，利用计算的电子能带结构计算了隧穿电流，即电子能带结构。在电场作用下，两个金属钛之间的电子通过薄的氧化镁层的隧穿。在金属钛/绝缘体氧化镁超晶格中测量了X射线光电子能谱，并讨论了它与价带态密度的关系。刻蚀前和刻蚀5min后的两个光谱显示出差异，反映了氧化镁层和钛层的电子态，与理论态密度符合得很好。这一XPS实验表明了我们理论电子结构计算的可靠性。