A Study On Preparation,Microstructrue And Magnetic Property Of Cu Doped ZnO DMS

ZnO-based diluted magnetic semiconductors (DMSs) play an important role in realizing the manipulation of electron’s charge and spin at the same time. It is a kind of preferred material for spinctronics device. How to develop ZnO-based DMS with room temperature ferromagnetism and make the spinctronics device applied at room temperature are the research hotspot. There are a lot of reports on room temperature ferromagnetism for ZnO-based DMS, but it is still controversial whether these observed ferromagnetism comes from the substitutional effect of doped ion or the precipitates such as clusters and/or secondary phase. This is because traditional analysis method like XRD can not detect the particular structure information of doped ion with the low concentration in ZnO-based DMS. Moreover, the microstructure of ZnO-based DMS plays an important role in understanding ferromagnetic origin. Therefore, it is a key for employing the analysis method with high sensitivity to study the microstucture of ZnO-based DMS. To avoid the precipitate problem, choosing non-magnetic ion like Cu as dopant is the attentive focus nowadays. In this thesis, Cu is used as dopant and microstructre and magnetic property for ZnO-based DMS are studied by SR-XRD and XAFS with high sensitivity combining with PIXE, XPS, Raman spectrum and AGM. Some valuable results as follows:1. Using coating film machine with magnetron sputtering restored and reconstructed by us, a series of Zn1-xCuxO films are prepared on the sapphire substrate by RF magnetron sputtering with composite target.2. Cu concentration is measured by PIXE. The result shows that besides Cu element, no other impurity like Mn、Fe、Co and Ni is found. Both traditional XRD and SR-XRD show that our samples has the wurtzite ZnO structure and no secondary phase such as Cu cluster or CuO、Cu2O is detected. EXAFS indicates that Cu incorporated into ZnO crystal lattice through substitution of Zn atoms. However, the substitution makes Zn1-xCuxO locate in the middle disorder state, which well agrees with the results from Raman. XPS spectrum has the typical satellite peak, which indicates the there must be substitutional Cu with+2valency that can provide local magnetic moment.3. The result from AGM shows that room temperature ferromagnetism obviously appears in Znl-xCuxO DMS. According to microstructure analysis, these observed ferromagnetism should be intrinsic not exterior. Due to destruction of long range lattice order and nonuniform distribution of substitutional Cu, the magnetic moment provided by Cu can not be fully utilized. Thus, the observed ferromagnetism of samples is smaller than the theoretic value. Taking account of the electric property of samples, the ferromagnetism of samples should be explained by the defect-mediated model.