钴掺杂氧化锌是室温稀磁半导体的重要候选材料,其磁学特性和钴掺杂浓度、显微结构及光学性质密切相关。磁控溅射具有成本低、易于大面积沉积高质量薄膜等特点,是广受关注的稀磁半导体薄膜制备方法。利用磁控溅射方法制备了不同浓度的钴掺杂氧化锌薄膜,并对其显微结构、光学性质和磁学特性进行了系统分析。结果表明: 当掺杂原子分数在8%以内时,钴掺杂氧化锌薄膜保持单一的铅锌矿晶体结构,钴元素完全溶解在氧化锌晶格之中;薄膜在可见光区域有很高的透射率,但在567, 615和659 nm处有明显吸收峰,这些吸收峰源于Co2+处于O2-形成的四面体晶体场中的特征d-d跃迁。磁学特性测试结果表明钴掺杂氧化锌薄膜具有室温铁磁性,且钴的掺杂浓度对薄膜的磁学特性有重要影响。结合薄膜结构、光学和电学性质分析,实验中观察到的室温铁磁性应源于钴掺杂氧化锌薄膜的本征属性,其铁磁耦合机理可由束缚磁极化子模型进行解释。

A systematic investigation on the microstructure, optical, and magnetic properties of Co-doped ZnO films is reported. Zn1-xCoxO films were synthesized using magnetron sputtering technique, which could produce economically feasible large area films with good crystalline properties even at a low substrate temperature. Structural analysis indicates that the wurtzite ZnO crystal can be well retained up to a Co composition of atom fraction 8%. All the samples show high transparency in the visible region. There are three absorption bands located on 567, 615, and 659 nm in the optical transmittance spectra for Co doped ZnO films, which correspond to the electronic transition of Co 3d orbitals in the oxygen tetrahedron, showing the incorporation of Co into the Zn sites in the wurtzite ZnO host lattice. The magnetic measurements indicate that all the Co doped ZnO films are ferromagnetic at room temperature and the concentration of Co doping plays an important role in the magnetic properties of Zn1-xCoxO thin films. Considering the structural, electrical, and magnetic investigations, the ferromagnetism observed in our samples should be an intrinsic property of Co doped ZnO films and can be described by bound magnetic polarons models with respect to defect-bound carriers.