金红石TiO_2中本征缺陷扩散性质的第一性原理计算  

Density functional theory calculation of diffusion mechanism of intrinsic defects in rutile TiO_2

作　　者：刘汝霖 方粮[1,2] 郝跃[3] 池雅庆[2] Liu Ru-Lin;Fang Liang;Hao Yue;Chi Ya-Qing(State Key Laboratory of High Performance Computing,National University of Defense Technology,Changsha 410073,China;College of Computer,National University of Defense Technology,Changsha 410073,China;State Key Discipline Laboratory of Wide Bandgap Semiconductor Technologies,School of Microelectronics,Xidian University,Xi＇an 710071,China)

机构地区：[1]国防科技大学高性能计算国家重点实验室,长沙410073 [2]国防科技大学计算机学院,长沙410073 [3]西安电子科技大学微电子学院宽禁带半导体材料与器件教育部重点实验室,西安710071

出　　处：《物理学报》2018年第17期198-205,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61332003);湖南省自然科学基金(批准号:2015JJ3024)资助的课题~~

摘　　要：基于密度泛函理论的爬坡弹性带方法,对金红石相二氧化钛晶体中钛间隙、钛空位、氧间隙、氧空位4种本征缺陷的扩散特征进行了研究.对比4种本征缺陷在晶格内部沿不同扩散路径的过渡态势垒后发现,缺陷扩散过程呈现出明显的各向异性.其中,钛间隙和氧间隙沿[001]方向具有最小的扩散势垒路径,激活能分别为0.505 eV和0.859 eV;氧空位和钛空位的势垒最小的扩散路径分别沿[110]方向和[111]方向,激活能分别为0.735 eV和2.375 eV.Diffusion mechanisms of four intrinsic point defects in rutile TiO2, titanium interstitial（TiI）, titanium vacancy（V（ti））, oxygen interstitial（OI） and oxygen vacancy（VO） are studied in the framework of density functional theory with quantum ESPRESSO suite. Diffusion processes are simulated by defect movement between two stable atomic configurations through using the climbing image nudged elastic band（CI-NEB） method.The initial and final atomic structure in the minimum energy path（MEP） are constructed with 3 × 3 × 4 perfect supercell matrix of 216 atoms. Considering that oxygen atoms build up TiO6 octahedron and half of the octahedral centers are occupied by Ti atoms in rutile, interstitial defect is constructed by adding one Ti or O atom to the empty oxygen octahedral center, and vacancy defect is constructed by removing one atom from crystal lattice grid. Structural relaxation is performed before performing the NEB calculation with gamma k point sampling in irreducible Brillouin zone with an energy cutoff of 650 eV. As rutile TiO2 has tetragonal symmetry（P42/mnm）, the diffusion channel along the [100] direction is equivalent to the [010] direction. Then, the diffusion paths along the direction parallel to c axis（[001] direction） and perpendicular to the c axis（[100] or [110] direction） are chosen to find the minimum diffusion energy path of TiI and OI. As for VTi and VO, diffusion paths are established from the vacancy site to nearest lattice site of the same kind.Calculation results exhibit significant anisotropy of energy barrier and diffusion mechanism. Of all defect species,TiI diffusion along the [001] direction through interstitial mechanism has the lowest activation barrier of 0.5057 eV.In addition, diffusions along the [100] and [110] direction through kick-out mechanism show higher energy barriers of1.0024 eV and 2.7758 eV, respectively. Compared with TiI, OI shows small barrier discrepancy between different diffusion directions, which is 0.859 eV along [001] and

关 键 词：金红石 本征缺陷 扩散 第一性原理 

分 类 号：O472[理学—半导体物理]