ZnMgO薄膜的结构、磁性及光学性质的研究

发布时间：2018-04-01 10:20

本文选题：ZnMgO薄膜　切入点：氧空位　出处：《山西师范大学》2015年硕士论文

【摘要】：稀磁半导体材料由于其在未来半导体自旋电子学器件中的巨大潜在应用而受到人们的广泛关注。近几年，3d过渡金属元素掺杂的具有室温铁磁性的宽禁带氧化物半导体材料取得了很大进展，但其磁性来源却一直存在较大争议。最近，非磁性元素掺杂或无掺杂氧化物薄膜的d0铁磁性引起人们的研究兴趣，在这类材料中，不需要考虑第二相磁性杂质对材料磁性的贡献，可以更好地研究材料缺陷等因素对氧化物薄膜磁性的影响。本论文利用脉冲激光沉积系统，在不同的沉积条件下制备出了多个系列的ZnMgO薄膜样品，研究了沉积氧压及靶材中Mg含量的改变对薄膜结构、磁性及光学带隙的影响；并在相同沉积氧压下探究了ZnMgO薄膜中氧空位、磁性与带隙间的关系；另外还研究了不同沉积氧压下制备的ZnMgCoO薄膜，，分析了沉积氧压对薄膜结构、磁学及光学性质的影响。主要研究内容如下：（1）我们选用脉冲激光沉积系统，在双抛Al2O3(0001)基片上制备了一系列沉积氧压递变的Zn0.9Mg0.1O薄膜，发现随沉积氧压的增大，薄膜沿c轴方向的晶格常数不断减小，对应的ZnO（002）峰逐渐向右偏移；而薄膜的带隙则随着沉积氧压的增大而减小，这是由于薄膜中的Mg含量与沉积氧压成反比；Zn0.9Mg0.1O薄膜材料的室温饱和磁化强度则呈现出一种先增大后减小的趋势，这可能与氧空位的浓度变化有关，本底真空生长的薄膜中缺陷种类较多，使得氧空位的有效浓度降低，影响了材料的磁性，在沉积氧压增加的过程中，氧空位浓度会出现一个最大值，然后逐渐减小。我们在相同的制备条件下沉积了一系列Zn0.85Mg0.15O薄膜，并得到了与上述变化规律一致的实验结果。此外，我们还选用Zn0.9Mg0.1O合金陶瓷靶材，在完全相同的沉积氧压下制备了一系列Zn0.9Mg0.1O薄膜材料，研究发现氧空位可以起到同时调控薄膜磁性及光学带隙的作用。薄膜中氧空位浓度越大，磁性越强，光学带隙越窄。（2）我们选用纯ZnO陶瓷靶材以及由固相反应法制得的Zn0.95Mg0.05O、Zn0.9Mg0.1O和Zn0.85Mg0.15O合金陶瓷靶材，分别在本底真空和20mTorr氧压下，以双抛Al2O3(0001)基片为衬底制备了多种Zn1-XMgXO薄膜样品，发现随靶材中Mg含量的增加，薄膜ZnO(002)峰对应的2θ值不断增大，这是由于Mg2+半径小于Zn2+半径所致；由于MgO的带隙远大于ZnO的带隙，薄膜中的Mg含量越高，薄膜的带隙也越大；然而，随Mg摩尔百分比（X）的增加，Zn1-XMgXO薄膜的室温饱和磁化强度呈现出先升高后降低的趋势，且在X=0.10时达到最大，导致这种变化规律的原因可能是由于Mg的加入使ZnO晶体中出现更多与室温铁磁性相关的点缺陷，而当Mg的含量过多时，ZnO晶体中的缺陷种类繁复，以致有效缺陷浓度降低所致。（3）选用脉冲激光沉积技术以双抛Al2O3(0001)基片为衬底，在不同的沉积氧压下制备了过渡金属Co掺杂的Zn0.85Mg0.10Co0.05O薄膜，发现随沉积氧压的增大，薄膜ZnO（002）峰逐渐向右偏移，带隙逐渐减小，室温铁磁性先升高后减低，与Zn0.9Mg0.1O和Zn0.85Mg0.15O薄膜的变化规律相同。
[Abstract]:In recent years , it is not necessary to consider the contribution of the second - phase magnetic impurities to the magnetic properties of oxide films .
The relationship between oxygen vacancy , magnetic and gap in ZnMgO thin films was investigated under the same oxygen pressure .
The effects of deposition oxygen pressure on film structure , magnetic properties and optical properties were studied . The main research contents were as follows :

( 1 ) We chose a pulsed laser deposition system to prepare a series of Zn0.9Mg0 . 1O films deposited with oxygen pressure on a double - cast Al2O3 ( 0001 ) substrate . It was found that the lattice constant of the film in the direction of the c - axis decreased with the increase of the deposition oxygen pressure , and the corresponding ZnO ( 002 ) peak shifted to the right ;
The band gap of the film decreases with the increase of the deposition oxygen pressure , because the Mg content in the film is inversely proportional to the deposition oxygen pressure ;
A series of Zn0 . 85Mg0 . 15O films were deposited under the same conditions .

( 2 ) We chose pure ZnO ceramic target and Zn0 . 95Mg0 . 05O , Zn0 . 9Mg0 . 1O and Zn0 . 85Mg0 . 15O alloy ceramic target prepared by solid phase reaction .
As the band gap of MgO is much larger than that of ZnO , the higher the Mg content in the film , the larger the band gap of the film .
However , with the increase of Mg mole percentage ( X ) , the room temperature saturation magnetization of the Zn1 - XMgXO thin film exhibits a tendency to decrease first and reach the maximum at X = 0.10 , which may cause more point defects in the ZnO crystal due to the addition of Mg , and when the content of Mg is too much , the type of defects in the ZnO crystal is complex , so that the effective defect concentration is reduced .

( 3 ) The Zn0 . 85Mg0 . 10Co0 . 05O films doped with the transition metal Co were prepared by pulsed laser deposition . The ZnO ( 002 ) peak was shifted to the right with increasing oxygen pressure , the band gap was gradually decreased , the room temperature ferromagnetism increased first and then decreased , which was the same as that of Zn0 . 9Mg0 . 1O and Zn0 . 85Mg0 . 15O films .

【学位授予单位】：山西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O649;TB383.2

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