Ferromagnetism in wide band gap materials Mn-ZnO and Mn-Si3N4 thin films

• Autores: Eva Céspedes Montoya
• Directores de la Tesis: Carlos A. Prieto Castro (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2009
• Idioma: inglés
• Tribunal Calificador de la Tesis: Francisco Jaque Rechea (presid.), Jesús Chaboy Nalda (secret.), Rafael Ramírez Jiménez (voc.), Agnes Traverse (voc.), José María González Calbet (voc.), María del Carmen Muñoz de Pablo (voc.), Francisco Javier García López (voc.)
• Materias:
  • Física
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • Contents 1. Introduction ..................................................................................1 1.1. State of the art ............................................................................1 1.2. Outlook of this dissertation ..........................................................................6 1.3. Dissertation structure .....................................................................................7 2. Thin Film Preparation Method and Experimental Techniques ...........................................................13 2.1. Sputtering technique ............................................................................................13 2.1.1. Experimental equipment .....................................................................17 2.2. SQUID magnetometry ...............................................................................20 2.3. X-Ray Diffraction (XRD) .............................................................................................21 2.4. X-Ray Reflectivity (XRR) ..............................................................................................22 2.5. Rutherford Backscattering Spectroscopy (RBS) .........................................................25 2.6. X-ray Absorption Spectroscopy (XAS) .........................................................26 2.6.1. XAS experiments at the Mn and Zn K -edges .............................................................27 2.6.1.1. X-Ray Absorption Near-Edge Structure (XANES)................................................................28 2.6.1.2. Extended X-Ray Absorption Fine Structure (EXAFS) ............................................29 2.6.2. XAS at the Mn L3,2 .edge..................................31 2.6.3. X-ray Magnetic Circular Dichroism (XMCD) .........................................................34 I. Mn-ZnO system 3. Mn/ZnO Multilayers .....................................................................................41 3.1. Motivation ................................................................................41 3.2. Preparation of multilayers ...............................................................42 3.3. Magnetic properties ......................................................................43 3.4. X-Ray Reflectivity (XRR) ..........................................................46 3.5. Rutherford Backscattering Spectroscopy (RBS) .........................................................50 3.6. X-Ray Diffraction (XRD) .................................................................................53 3.7. Transmission Electron Microscopy (TEM) ............................................................................58 3.8. X-Ray Absorption Spectroscopy (XAS) ...............................................................61 3.8.1. X-Ray Absorption Near-Edge Structure (XANES) ......................................................61 3.8.2. Extended X-Ray Absorption Fine Structure (EXAFS) ..........................................64 3.9. Structural and magnetic scheme .................................................................73 3.10. Conclusions .........................................................................................77 4. MnOx/ZnO Multilayers.....................................................................81 4.1. Motivation....................................................................................81 4.2. Preparation of multilayers ..................................................................................81 4.3. Magnetic properties ...............................................................................82 4.4. Rutherford Backscattering Spectroscopy (RBS) ..................................................................83 4.5. X-Ray Reflectivity (XRR) ...............................................................85 4.6. X-Ray Diffraction (XRD) .......................................................................86 4.7. X-Ray Absorption (XAS) ........................................................................88 4.7.1. XANES at the Mn K-edge ..................................................89 4.7.2. XAS at the Mn L3,2-edge .............................................................90 4.8. Thermal post-deposition annealing ......................................................91 4.9. Discussion and remarks: The origin of FM in MnOx/ZnO multilayers versus the origin in the so-called Mn/ZnO multilayers ...................................................92 4.10. Conclusions ...........................................................98 5. Mn:ZnO Thin Films ........................................................101 5.1. Motivation .............................................................................101 5.2. Preparation of Mn:ZnO films ......................................................102 5.3. X-Ray Reflectivity (XRR) .............................................................104 5.4. Rutherford Backscattering Spectroscopy (RBS) ................................................106 5.5. X-Ray Diffraction (XRD)..........................................................107 5.6. Magnetic properties ............................................................109 5.7. X-Ray Absorption Near-Edge Structure (XANES).....................................................111 5.8. UV-VIS Absorption .........................................................................115 5.9. Conclusions .........................................117 A. Effect of Thermal Treatments and Substrate Temperature on Mn/ZnO Multilayers..................................................................121 B. ZnO Crystal Structures ...............................................143 II. Mn-Si3N4 system 6. Mn/Si3N4 Multilayers ....................................................147 6.1. Motivation ...............................................147 6.2. Preparation of multilayers ....................................................149 6.3. X-Ray Reflectivity (XRR) ......................................................150 6.4. Transmission Electron Microscopy (TEM) .........................................153 6.5. Rutherford Backscattering Spectroscopy (RBS) and Nuclear Reaction Analysis (NRA) .................................................................154 6.6. Magnetic properties .............................................................156 6.7. X-Ray Photoemission Spectroscopy (XPS) .....................................................159 6.8. X-Ray Absorption Spectroscopy (XAS) ......................................................161 6.8.1. X-Ray Absorption Near-Edge Structure (XANES) ...........................................162 6.8.2. Computational methods: XANES simulations ....................................................164 6.8.3. Extended X-Ray Absorption Fine Structure (EXAFS) ........................................................169 6.8.4. XAS at the Mn L3,2-edge and XMCD .....................................................172 6.9. Remarks and discussion ....................................................................175 6.10. Conclusions ..................................................................178 C. From Ferromagnetism to Noble Metal Nanoparticles Formation in Si3N4 and ZnO Systems .................................................. 183 C.1. Au/Si3N4 Multilayers .....................................................................................................183 C.1.1. Motivation ...............................................................................................................183 C.1.2. Preparation of samples ..........................................................................................185 C.1.3. X-Ray Reflectivity (XRR) .....................................................................................186 C.1.4. Rutherford Backscattering Spectroscopy (RBS) .............................................188 C.1.5. X-Ray Absorption Spectroscopy (XAS) ............................................................190 C.1.5.1. X-Ray Absorption Near-Edge Structure (XANES) .........................190 C.1.5.2. Extended X-Ray Absorption Fine Structure (EXAFS) ....................191 C.1.6. Grazing Incidence Small Angle X-ray Scattering (GISAXS) .........................193 C.1.7. UV-VIS Absorption ................................................................................................198 C.1.8. Conclusions ..............................................................................................................203 C.2. Au/ZnO Multilayers .......................................................................................................207 C.2.1. Motivation ...............................................................................................................207 C.2.2. Preparation of samples ...........................................................................................207 C.2.3. X-Ray Reflectivity (XRR) ......................................................................................209 C.2.4. Rutherford Backscattering Spectroscopy (RBS) ..............................................212 C.2.5. X-Ray Absorption Spectroscopy (XAS) .............................................................213 C.2.5.1. X-Ray Absorption Near-Edge Spectroscopy (XANES) ..................213 C.2.5.2. Extended X-Ray Absorption Fine Structure (EXAFS) ....................213 C.2.6. X-Ray Diffraction (XRD) ......................................................................................215 C.2.7. Grazing Incidence Small Angle X-ray Scattering (GISAXS) .........................218 C.2.8. UV-vis Absorption ..................................................................................................221 C.2.9. Conclusions ..............................................................................................................223