Si-based diluted magnetic semiconductors X-ray absorption spectroscopy study

　　Title: Si-based diluted magnetic semiconductors X-ray absorption spectroscopy study
　　Author: Jiang Yong
　　Degree awarded: China University of Science and Technology
　　Keywords: X-ray absorption fine structure;; Fe_xSi_ (1-x);; Mn_xSi_ (1-x);; diluted magnetic semiconductors;; magnetron sputtering;; molecular beam epitaxy;; XRD;; Raman
　　Abstract:
　　This thesis using synchrotron radiation X-ray absorption fine structure spectroscopy (XAFS) technique, combined with X-ray diffraction (XRD) and Raman spectroscopy joint study of experimental methods of sputtering magnetron sputtering and molecular beam epitaxy prepared Si-based diluted magnetic semiconductor thin film structure, to obtain the Fe-doped and Mn-doped Si-based thin films Fe and Mn atoms in the distribution and structural Neodymium Magnets parameters such as coordination environment. At the same time an effective single-particle-based self-consistent real space relativistic Green's function of FEFF8 theoretical calculations, and Mn atoms by Fe atoms doped Si-based diluted magnetic semiconductor system Fe atoms and Mn atoms occupying the typical building model, analysis the Fe atom and Mn atom in the system and the mass of the existing form, clear the Fe atom and Mn-doped Si-based diluted magnetic semiconductor thin films of Mn atoms mainly substitutional form, Fe atoms exist in the form is determined by the temperature of the sample preparation. These are Si-based diluted magnetic semiconductors provide a basis for the controllable preparation.
　　1.Fe doped Si-based diluted magnetic semiconductor thin film structure
　　The use of XAFS and Raman spectroscopy and other methods of magnetron sputtering deposition method were prepared Fe_xSi_ (1-x) thin film magnetic semiconductor structures. Raman results show that the samples prepared at room temperature does not exist in the metal clusters or Fe-Si Fe compound phase, 473K temperature prepared samples have FeSi_2 compound phase exists. Program to simulate the use of FEFF8 Fe occupy Si lattice substitution bit, square and hexagonal interstitial space bit, three theoretical models most representative of the radial structure function curve, compared with the experimental curve, a clear presence of Fe in the sample form depends on the sample preparation temperature. Preparation of the samples at room temperature, Fe atoms into the Si lattice, the main alternative to digital form Fesi exist; and when the preparation temperature reaches 473K, the Fe film samples mainly FeSi_2 compounds form. At the same time, the use of XAFS 473K under the conditions studied, using molecular beam epitaxy prepared Fe_xSi_ (1-x) thin film magnetic semiconductor structure, the findings with previous results obtained are consistent, that is, when the temperature reached 473K, after preparation, Fe Si atoms distributed to the media, the major reaction with Si http://www.everbeenmagnet.com/en/products/110-sintered-neodymium-magnets atoms to produce FeSi_2 compounds.
　　2.Mn doped Si-based diluted magnetic semiconductor thin film structure
　　Of XRD and XAFS study prepared under the conditions of 473K Mn_xSi_ (1-x) thin film magnetic semiconductor structures. XRD results show that two different Mn contents of samples do not exist in clusters or metal Mn Mn-Si compound phase. Mn K edge XAFS results show that for all Mn-doped content (3.0%, 10.0%) samples, Mn Si atoms are already distributed to the media. EXAFS fitting results show that, Mn atoms with nearest neighbor Si atoms with average bond length is 2.35 (?), With a median of about 4.1, and Mn occupy the alternative position of the structural parameters are similar. Simulation program using FEFF8 Si lattice of Mn atoms occupy the alternative position, square and hexagonal interstitial gap-bit, three theoretical models most representative of the radial structure function curve, compared with the experimental curve, clear of Mn atoms in the sample to replace the main bit of form.
　　Degree Year: 2009