Dissertation > Excellent graduate degree dissertation topics show

Computing Studies on Magnetic Properties and Electronic Structure of Rare Earths (Gd, La, Y) Doped Materials Based on Density Function Theory

Author: YanKai
Tutor: ZhaoHaoFeng
School: Nanjing University of Information Engineering
Course: Applied Mathematics
Keywords: Density functional theory Rare Earth Elements Zinc oxide Diluted magnetic semiconductors p-type
CLC: O482.51
Type: Master's thesis
Year: 2011
Downloads: 116
Quote: 0
Read: Download Dissertation

Abstract


Based on density functional theory a First Principle package Materials Studio CASTEP for rare earth elements Re (Re = Y, La, Gd) doped oxygen vacancies (Vo) and rare earth elements Re (Re = Y La, Gd) coexist, rare earth element Re (Re = Y, La, Gd) respectively, co-doped with C and N 2 × 2 × 2 zinc oxide supercell changes in cell structure, electronic structure, magnetic properties, optical properties calculated . Finally, through analysis and comparison to experiment developed characteristics of p-type zinc oxide dilute magnetic semiconductor provide some guidance, at the same time reveal the physical mechanism behind the related phenomena. Concluded that the analysis of this paper is as follows: rare earth Y single-doped zinc oxide supercell weak moment 0.02μB. Rare Earth La doped zinc oxide supercell, although the cause local spin polarization of the atoms, but did not appear magnetic supercell. Rare earth elements Gd single doped zinc oxide supercell magnetic moment significantly increased 7μB band gap of 0.133eV. Overall, Vo supercell improve magnetic properties of rare earth elements Re doping has little effect on the magnetic supercell mainly from the rare-earth doped own. This is mainly the role of the half full 4f electron shell, in addition, the rare earth-doped more performance for a trivalent donor forms exist, while Vo As another donor forms exist, which will cause the ZnO semiconductor rendered n-type characteristics, making doped miscellaneous supercell Fermi level into the top of the valence band. Therefore, irrespective of the single rare earth doped the coexistence Vo and Re (Re = Y, La, Gd), zinc oxide supercell are unable to achieve p-type. REE Re (Re = Y, La, Gd) with N-doped zinc oxide supercell, can effectively increase the supercell band gap, but the improvement effect of the supercell magnetic moment little supercell the magnetic moments of still the main source of in doped rare earth elements. Calculated, Gd-N co-doped zinc oxide supercell higher the magnetic moment 6.96μB well as the wide band gap of 0.608eV. This is mainly due to N as by the presence of impurities, and can effectively absorb REE produce free electrons. Thus, Gd-N of zinc oxide-doped zinc oxide semiconductor of a p-type as well as improvement of the magnetic moments conducive supercell. The rare earth elements Re (Re = Y, La, Gd) and C co-doped zinc oxide supercell, can effectively improve the supercell magnetic moment, especially YC, La-C co-doped magnetic moment of the system relative Y-, La single mixed with improved significantly, which Gd-C co-doped zinc oxide supercell magnetic moment up to 8.0μB. However, co-doped with C elements the supercell band gap disappeared. This is mainly due to the rare earth element Re (Re = Y, La, Gd) larger radius, which can easily lose the valence electrons. Secondly, C atomic radius is larger than N, and C atomic number smaller than N 1, C-2p orbit can accommodate four electrons, but the binding force of electronic without N. Again, C-doped although able to absorb and reduce the free electrons generated by the rare earth element, but it also can make the increase in the number of the hole carriers, thereby improving the system conductivity, and eventually causes the disappearance of the system band gap. In addition, rare earth element Re element doped the supercell level position of the optical properties of the principal effects of ZnO, and the peak strength, the same time, so that the doped systems, a significant change in the optical properties of the high energy region. N, C alternative O bit doped ZnO supercell such that the system has significant changes in the optical properties of the low-energy region. This change was mainly due to the N, C doping at the Fermi level due to the impurity level.

Related Dissertations

  1. The Research on Space Organization and Combination of the Multiplex Cinema Builders,TU242.2
  2. The Research of Steel’s Representation in Architecture,TU-0
  3. Research of ZigBee Node Used in Smart Home,TN929.5
  4. The Value of the Heart-Type Fatty Acid Binding Protein in Early Diagnosis of Acute Myocardial Infarction,R542.22
  5. Blockage type of rheumatoid arthritis clinical research for Zhou Naiyu academic thinking and clinical experience and Bi Yu Kang I,Treatment of late alpine,R259
  6. Clinical observation of the phlegm Jiangni Treated phlegm vertigo vertigo,R255.3
  7. C-reactive protein,homocysteine ??levels in type 2 diabetic peripheral neuropathy of TCM,R259
  8. Platelet parameters in patients before and after acute myocardial infarction,R542.22
  9. Professor Zhang Shuwen academic thinking,and 59 cases of Chinese and Western medicine combined with clinical research for diagnosis and treatment of acute pancreatitis,R249.2
  10. Analyiss on Dicharge Environment and the Effect of of Dust Electrostatic Coagualation,X701.2
  11. Distribution of the Contents of Pectin and Cellulose and Their Effect on Smoking Quality in Flue-cured Tobacco of China,S572
  12. The Automatic Variable Fertilization System Based on the Steeper Motor,S224.2
  13. Analysis on Characteristics and Discriminant of Aroma Types of Flue-Cured Tobacco,S572
  14. The Thought of Environment Ethics on Two Type Society Construction,B82-058
  15. Effect of Simulating Soil Environment on Soil Bacterial Diversity by PCR-RFLP Analysis,S154.3
  16. Transcriptional Regulation of Genes Encoding MFS by LysR in Vibrio Cholerae,R378
  17. The Degradation of PET to Synthesize Phosphate Flame Retardants and the Study of Their Flame-retardant Performance,TQ314.248
  18. Study on the Design of Magnetic Drum Planting Machine for Tobacco,S223.2
  19. Effects of Host Body Size and Age on Preference and Development Performance in Brachymeria Lasus (Hymenoptera: Chalcididae),S476.3
  20. Phylogenic Analysis of Henan Populations and Feeding Behavior Comparison of Bemisia Tabaci B and Q Biotypes,S433
  21. QTL Mapping of Plant-type and Flowering Related Traits Using a Four-way Cross Population in Maize,S513

CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Solid nature of the > Magnetic properties > Magnetic theory
© 2012 www.DissertationTopic.Net  Mobile