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A.1. EuO-related phases and cubic oxide substrates 129 Figure A.2.: Structure and (001) plane of yttria-stabilized zirconia (YSZ). In the following, we describe the crystal structure of substrates used in this thesis. Yttriastabilized zirconia (YSZ) is used as a seed for coherent EuO growth of reference quality. Pure zirconium dioxide (ZrO 2 ) undergoes a phase transformation from monoclinic (stable at the room temperature) to tetragonal (at about 1000 ◦ C) and then to cubic (at about 2370 ◦ C). A stabilization of the desired cubic phase of zirconia can be accomplished by substitution of some of the Zr 4+ ions (ionic radius of 0.82 Å, too small for ideal cubic lattice) in the crystal lattice with slightly larger ions, e. g. those of Y 3+ (ionic radius of 0.96 Å). The result is cubic yttria-stabilized zirconia (YSZ). Doping with Y 3+ ions produces oxygen vacancies, as three O 2− ions are bound to Y 3+ rather than four O 2− ions in case of Zr 4+ . This permits YSZ to conduct O 2− ions (and thus conduct an electrical current), provided there is a sufficient vacancy site mobility, a property that increases with temperature. 227 Figure A.3.: Rhombohedral structure, conversion, and pseudocubic structure with (001) plane of LaAlO 3 (LAO). Pseudocubic LaAlO 2 (LAO) is used for epitaxial EuO/LAO (100) heterostructures with tensile biaxial strain. The transformation between rhombohedral and cubic structure for LAO is illustrated in Fig. A.3b. 218 The LAO (100) cubic plane is parallel to the (0¯12) rhomb plane, and [01¯1] cubic ‖ [100] rhomb and [011] cubic ‖ [121] rhomb . The LAO substrates are cut along (100) cubic planes. We will use the cubic indexing for LAO in this work. LAO is rhombohedral (pseudocubic) at room temperature, and undergoes a structural displacement transition at ∼540 ◦ C. 164
130 A. Appendix The MgO and Si cubic unit cells rely on the well-known rock-salt and diamond lattice, respectively, and are not further discussed. A.2. In situ analysis of the Si (001) surface after different treatments, conducted by Auger electron spectroscopy In order to control the chemical quality of Si (001) surfaces in our studies, we conduct Auger electron spectroscopy (AES) routinely on clean (i. e. after a flashing procedure) and in situ surface-passivated Si substrates. The results of AES are summarized in Fig. A.4. Untreated Si (“as introduced”) shows a large fraction of oxidized silicon (a). Here, the Si peak is hardly observable, according to a closed native SiO 2 surface layer. DHF-etched Si has a reduced oxide signal (b), however, this procedure introduces C contaminations. Flashed Si (c) is observed to be chemically clean and serves as a reference. The same is true for Si after an in situ hydrogen passivation (d, e), whereas an oxygen contribution near the detection limit can be observed.
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Member of the Helmholtz Association
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Forschungszentrum Jülich GmbH Pete
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Zusammenfassung In dieser Doktorarb
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Contents 1. Introduction 1 2. Theor
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List of Figures 2.1. Phase diagram
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List of Figures xi 5.12. Resulting
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1. Introduction Smart and powerful
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3 In the thesis at ha
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2. Theoretical background . . . The
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2.1. The challenge of stabilizing s
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2.2. Electronic structure of EuO 9
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2.3. Magnetic properties of EuO 11
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2.4. Hard X-ray photoemission spect
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2.5. Magnetic circular dichroism in
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3. Experimental details Die Pläne
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3.1. Molecular beam epitaxy for oxi
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3.2. In situ characterization techn
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3.2. In situ characterization techn
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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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Page 102 and 103: 5. Results II: The integration of t
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Page 140 and 141: 6. Conclusion and Outlook In the th
Page 142 and 143: 125 Outlook and perspectives In the
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Page 150 and 151: Bibliography 133 [13] S. S. P. Park
Page 152 and 153: Bibliography 135 [36] R. E. Dickers
Page 154 and 155: Bibliography 137 [65] R. Sutarto, S
Page 156 and 157: Bibliography 139 [91] P. Braun, M.
Page 158 and 159: Bibliography 141 [116] S. Hüfner.
Page 160 and 161: Bibliography 143 [144] R. Feder and
Page 162 and 163: Bibliography 145 [171] H. Miyazaki,
Page 164 and 165: Bibliography 147 [197] J. Qi, T. Ma
Page 166 and 167: Software and Internet Resources [21
Page 168 and 169: List of own publications 151 [10] R
Page 170 and 171: List of conference contributions 15
Page 172 and 173: Schriften des Forschungszentrums J
Page 175: Schlüsseltechnologien / Key Techno
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