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Contents 1. Introduction 1 2. Theoretical background 5 2.1. The challenge of stabilizing stoichiometric europium oxide ........... 5 2.2. Electronic structure of EuO .............................. 8 2.2.1. The open shell 4f 7 .............................. 9 2.2.2. Valence band, band gap, and conduction bands .............. 10 2.3. Magnetic properties of EuO ............................. 11 2.3.1. The Curie temperature of EuO ........................ 14 2.3.2. Thin film effects in EuO ........................... 15 2.3.3. Spin filter tunneling in EuO ......................... 16 2.4. Hard X-ray photoemission spectroscopy ...................... 18 2.4.1. The three-step model of photoemission .................. 19 2.4.2. Spectral features and their interpretation ................. 23 2.4.3. Implications of hard X-ray excitation .................... 25 2.5. Magnetic circular dichroism in core-level photoemission ............. 29 2.5.1. Atomic multiplet theory including MCD .................. 29 2.5.2. Coupling schemes of angular momenta in Eu 2+ core-levels ....... 31 3. Experimental details 35 3.1. Molecular beam epitaxy for oxides ......................... 35 3.2. In situ characterization techniques ......................... 38 3.2.1. Reflection high-energy electron diffraction ................. 38 3.2.2. Low-energy electron diffraction ....................... 40 3.2.3. Auger electron spectroscopy ......................... 41 3.3. Experimental developments at the Oxide-MBE setup ............... 42 3.4. Ex situ characterization techniques ......................... 45 3.4.1. Superconducting quantum interference device magnetometry ..... 45 3.4.2. X-ray diffraction methods .......................... 46 3.4.3. Hard X-ray photoemission spectroscopy .................. 48 3.4.4. Depth-selective profiling with HAXPES .................. 51 3.4.5. Hard X-ray circular magnetic dichroism in photoemission ........ 55 vii
viii Contents 4. Results I: Single-crystalline epitaxial EuO thin films on cubic oxides 57 4.1. Coherent growth: EuO on YSZ (100) ........................ 60 4.1.1. Thickness-dependent magnetic properties of EuO thin films ...... 64 4.1.2. Preparation on conductive YSZ substrates ................. 66 4.1.3. HAXPES core-level spectra of single-crystalline EuO/cYSZ ....... 68 4.1.4. Magnetic circular dichroism of single-crystalline EuO/cYSZ ...... 71 4.2. Lateral tensile strain: EuO on LaAl 3 (100) ..................... 74 4.3. Lateral compressive strain: EuO on MgO (100) .................. 79 4.4. Summary ........................................ 84 5. Results II: EuO integration directly on silicon 85 5.1. Chemical stabilization of bulk-like EuO directly on silicon ............ 86 5.2. Thermodynamic analysis of the EuO/Si interface ................. 96 5.3. Interface engineering I: Hydrogen passivation of the EuO/Si interface ..... 105 5.4. Interface engineering II: Eu passivation of the EuO/Si interface ......... 111 5.5. Interface engineering III: SiO x passivation of the EuO/Si interface ....... 117 5.6. Summary ........................................ 121 6. Conclusion and Outlook 123 A. Appendix 126 A.1. EuO-related phases and cubic oxide substrates .................. 126 A.2. In situ analysis of the Si (001) surface by AES ................... 130 Bibliography 132 Software and Internet Resources 149 List of own publications 150 List of conference contributions 152
Page 1 and 2: Member of the Helmholtz Association
Page 4 and 5: Forschungszentrum Jülich GmbH Pete
Page 6: Zusammenfassung In dieser Doktorarb
Page 12 and 13: List of Figures 2.1. Phase diagram
Page 14: List of Figures xi 5.12. Resulting
Page 18 and 19: 1. Introduction Smart and powerful
Page 20 and 21: 3 In the thesis at ha
Page 22 and 23: 2. Theoretical background . . . The
Page 24 and 25: 2.1. The challenge of stabilizing s
Page 26 and 27: 2.2. Electronic structure of EuO 9
Page 28 and 29: 2.3. Magnetic properties of EuO 11
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Page 46 and 47: 2.5. Magnetic circular dichroism in
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3.3. Experimental developments at t
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3.4. Ex situ characterization techn
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4. Results I: Single-crystalline ep
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59 Table 4.1.: Parameters for stoic
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4.1. Coherent growth: EuO on YSZ (1
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4.2. Lateral tensile strain: EuO on
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4.2. Lateral tensile strain: EuO on
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4.3. Lateral compressive strain: Eu
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5. Results II: The integration of t
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5.1. Chemical stabilization of bulk
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5.2. Thermodynamic analysis of the
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5.3. Interface engineering I: Hydro
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5.4. Interface engineering II: Eu p
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5.5. Interface engineering III: SiO
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5.5. Interface engineering III: SiO
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5.6. Summary 121
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6. Conclusion and Outlook In the th
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125 Outlook and perspectives In the
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A.1. EuO-related phases and cubic o
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A.1. EuO-related phases and cubic o
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A.2. In situ analysis of the Si (00
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Bibliography 133 [13] S. S. P. Park
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Bibliography 135 [36] R. E. Dickers
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Bibliography 137 [65] R. Sutarto, S
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Bibliography 139 [91] P. Braun, M.
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Bibliography 141 [116] S. Hüfner.
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Bibliography 143 [144] R. Feder and
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Bibliography 145 [171] H. Miyazaki,
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Bibliography 147 [197] J. Qi, T. Ma
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Software and Internet Resources [21
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List of own publications 151 [10] R
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List of conference contributions 15
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Schriften des Forschungszentrums J
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