Fe掺杂ZnO基稀磁半导体微结构和铁磁性的研究

发布时间：2018-05-28 02:02

  本文选题：稀磁半导体 + 磁控溅射　； 参考：《西北师范大学》2015年硕士论文

【摘要】：ZnO作为一种性能优良的宽带隙半导体材料,具有较高居里温度以及室温铁磁性而成为制备稀磁半导体的重要材料之一,因过渡金属掺杂的Zn O基稀磁半导体材料同时具备电子的电荷特性和自旋特性,使其在自旋电子学和光电子领域具有广泛应用前景。利用其电学性质可制作高速缓冲存储器;利用其磁学性质可制作出永久性信息存储器,使其有望成为新一代信息存储的载体。本论文利用磁控溅射制备了Fe掺杂ZnO半导体样品,研究了Fe的掺杂量、退火温度、退火气氛对样品的微结构和室温铁磁性的影响,将纳米薄膜的微结构缺陷和铁磁性联系起来,对Fe掺杂ZnO纳米薄膜室温铁磁性的来源进行了解释。1.采用磁控溅射法在Si衬底上制备了纯ZnO和Zn1-xFexO(x=1.0%,3.0%,5.0%,7.0%)纳米薄膜,分别在真空和空气中用不同温度对样品进行退火处理后得到Fe掺杂ZnO稀磁半导体纳米薄膜材料。利用X光衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、以及X射线光电子能谱仪(XPS)和振动样品磁强计(VSM)对样品的微结构、表面形貌、元素成分、元素化学价态和室温铁磁特性进行测试。2.XRD测试结果表明,样品均为六角纤锌矿结构,沿c轴择优生长,Fe掺杂量和退火温度对薄膜微结构有一定程度的影响,随着Fe掺杂量的增加,样品的衍射峰强度先增大后减小,薄膜中的应力逐渐增大,晶粒尺寸逐渐减小;当退火温度为450oC时,出现了最强的(002)衍射峰,晶粒大小变为最大,薄膜的结晶度和取向性都明显变好,之后随着退火温度的上升薄膜晶粒变小,衍射峰强明显变弱。利用SEM对样品表面形貌和断面观测结果表明,Fe的掺杂能提高ZnO:Fe纳米薄膜的晶粒均匀性和表面致密性;随着退火温度的升高,薄膜表面平整性逐渐改善,晶粒变大,但大小仍不均匀。薄膜厚度随着掺杂浓度的增大先增加后减小,退火温度和气氛对薄膜的生长有一定的影响,空气中450℃温度退火时薄膜平均厚度为最大。通过对其EDS谱的分析,确定我们成功将Fe掺入ZnO纳米薄膜中,并且XPS分析发现Fe在薄膜中以Fe2+和Fe3+两种价态存在。3.利用VSM对薄膜的铁磁性进行了测量,结果表明所有样品均出现一条S形的完整的磁滞回线,说明具有较明显的室温铁磁性。Fe元素的掺杂量、退火温度、退火气氛均对薄膜铁磁性有一定程度的影响。随着Fe元素的掺杂量增加,薄膜饱和磁化强度逐渐减小,但仍大于纯Zn O薄膜的饱和磁化强度;随着退火温度的上升,薄膜磁化强度有逐渐增大的趋势;空气中退火的样品磁化强度均小于纯ZnO薄膜的磁化强度。对其铁磁性用缺陷与周围的磁性离子形成的束缚磁极化子(BMP)理论进行了解释。
[Abstract]:As a kind of wide band gap semiconductor material with excellent properties, ZnO is one of the important materials for preparing dilute magnetic semiconductors due to its high Curie temperature and ferromagnetism at room temperature. ZnO-based diluted magnetic semiconductors doped with transition metals have both charge and spin properties of electrons, which makes them widely used in the fields of spin electronics and optoelectronics. Cache memory can be made by using its electrical property, and permanent information memory can be made by using its magnetic property, which is expected to become the carrier of the new generation of information storage. In this paper, Fe doped ZnO semiconductor samples were prepared by magnetron sputtering. The effects of Fe doping amount, annealing temperature and annealing atmosphere on the microstructure and room temperature ferromagnetism of the samples were studied. The source of room temperature ferromagnetism of Fe doped ZnO nanocrystalline films was explained. Pure ZnO and Zn1-xFexOX1.0 nanocrystalline films were prepared on Si substrates by magnetron sputtering. Fe doped ZnO thin films were prepared by annealing in vacuum and air at different temperatures. The microstructure, surface morphology and elemental composition of the samples were characterized by X-ray diffractometer, scanning electron microscope (SEM), energy spectrometer (EDS), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The chemical valence state of elements and ferromagnetic properties at room temperature were measured. 2. The results of XRD showed that the samples were hexagonal wurtzite structure, and the doping amount of Fe and annealing temperature along the c-axis had some influence on the microstructure of the films. With the increase of Fe doping content, the diffraction peak intensity of the sample first increases and then decreases, the stress in the film increases gradually, the grain size decreases gradually, and the strongest diffraction peak appears when the annealing temperature is 450oC, and the grain size becomes the largest. The crystallinity and orientation of the films improved obviously, and the diffraction peak strength became weaker with the increase of annealing temperature. The results of surface morphology and cross section observation by SEM show that the doping of Fe can improve the grain uniformity and surface compactness of ZnO:Fe nanocrystalline films, and with the increase of annealing temperature, the surface smoothness and grain size of the films are improved gradually. But the size is still uneven. The thickness of the films increases first and then decreases with the increase of doping concentration. Annealing temperature and atmosphere have a certain influence on the growth of the films. The average thickness of the films annealed at 450 鈩，

本文编号：1944760