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The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.

The interface formation between PbTiO₃ and SrTiO₃ has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1eV, corresponding to a conduction band offset of 1.3±0.1eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO₃ and PbTiO₃ surfaces. The observed band offsets are also in line with a ~1.1eV difference in barrier heights of PbTiO₃ in contact with different electrode materials as compared to barrier heights of SrTiO₃ with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO₃ and PbTiO₃, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO₃ is consistent with the metallic conduction of donor doped or reduced SrTiO₃, while barrier heights ≳1eV for PbTiO₃ are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties.

The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.

The interface formation between PbTiO₃ and SrTiO₃ has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1eV, corresponding to a conduction band offset of 1.3±0.1eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO₃ and PbTiO₃ surfaces. The observed band offsets are also in line with a ~1.1eV difference in barrier heights of PbTiO₃ in contact with different electrode materials as compared to barrier heights of SrTiO₃ with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO₃ and PbTiO₃, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO₃ is consistent with the metallic conduction of donor doped or reduced SrTiO₃, while barrier heights ≳1eV for PbTiO₃ are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties.

The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.

The interface formation between PbTiO₃ and SrTiO₃ has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1eV, corresponding to a conduction band offset of 1.3±0.1eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO₃ and PbTiO₃ surfaces. The observed band offsets are also in line with a ~1.1eV difference in barrier heights of PbTiO₃ in contact with different electrode materials as compared to barrier heights of SrTiO₃ with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO₃ and PbTiO₃, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO₃ is consistent with the metallic conduction of donor doped or reduced SrTiO₃, while barrier heights ≳1eV for PbTiO₃ are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties.

The interface formation between PbTiO₃ and SrTiO₃ has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1eV, corresponding to a conduction band offset of 1.3±0.1eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO₃ and PbTiO₃ surfaces. The observed band offsets are also in line with a ~1.1eV difference in barrier heights of PbTiO₃ in contact with different electrode materials as compared to barrier heights of SrTiO₃ with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO₃ and PbTiO₃, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO₃ is consistent with the metallic conduction of donor doped or reduced SrTiO₃, while barrier heights ≳1eV for PbTiO₃ are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties.

The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.

The interface formation between PbTiO₃ and SrTiO₃ has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1eV, corresponding to a conduction band offset of 1.3±0.1eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO₃ and PbTiO₃ surfaces. The observed band offsets are also in line with a ~1.1eV difference in barrier heights of PbTiO₃ in contact with different electrode materials as compared to barrier heights of SrTiO₃ with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO₃ and PbTiO₃, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO₃ is consistent with the metallic conduction of donor doped or reduced SrTiO₃, while barrier heights ≳1eV for PbTiO₃ are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties.

The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.

The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.

The interface formation between PbTiO₃ and SrTiO₃ has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1eV, corresponding to a conduction band offset of 1.3±0.1eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO₃ and PbTiO₃ surfaces. The observed band offsets are also in line with a ~1.1eV difference in barrier heights of PbTiO₃ in contact with different electrode materials as compared to barrier heights of SrTiO₃ with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO₃ and PbTiO₃, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO₃ is consistent with the metallic conduction of donor doped or reduced SrTiO₃, while barrier heights ≳1eV for PbTiO₃ are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties.

The interface formation between Ba₀.₆Sr₀.₄TiO₃ and Al₂O₃ has been studied using photoelectron spectroscopy with in situ sample preparation. A negligible valence band discontinuity, corresponding to a ∼5.6 eV barrier for electron transport at the BST/Al₂O₃ interface is determined. Current-voltage measurements show that the leakage current can be significantly reduced by inserting the Al₂O₃ barrier layer between barium strontium titanate (BST) and Pt electrode. Different charge injection behavior depending on Al₂O₃ thickness is observed, which correspond well with the experimentally determined energy band diagrams. Direct tunneling from the metal electrode into the BST conduction band through the Al₂O₃ barrier layer is observed.

The interface formation between Ba₀.₆Sr₀.₄TiO₃ and Al₂O₃ has been studied using photoelectron spectroscopy with in situ sample preparation. A negligible valence band discontinuity, corresponding to a ∼5.6 eV barrier for electron transport at the BST/Al₂O₃ interface is determined. Current-voltage measurements show that the leakage current can be significantly reduced by inserting the Al₂O₃ barrier layer between barium strontium titanate (BST) and Pt electrode. Different charge injection behavior depending on Al₂O₃ thickness is observed, which correspond well with the experimentally determined energy band diagrams. Direct tunneling from the metal electrode into the BST conduction band through the Al₂O₃ barrier layer is observed.

The interface formation between Ba₀.₆Sr₀.₄TiO₃ and Al₂O₃ has been studied using photoelectron spectroscopy with in situ sample preparation. A negligible valence band discontinuity, corresponding to a ∼5.6 eV barrier for electron transport at the BST/Al₂O₃ interface is determined. Current-voltage measurements show that the leakage current can be significantly reduced by inserting the Al₂O₃ barrier layer between barium strontium titanate (BST) and Pt electrode. Different charge injection behavior depending on Al₂O₃ thickness is observed, which correspond well with the experimentally determined energy band diagrams. Direct tunneling from the metal electrode into the BST conduction band through the Al₂O₃ barrier layer is observed.

The interface formation between Ba₀.₆Sr₀.₄TiO₃ and Al₂O₃ has been studied using photoelectron spectroscopy with in situ sample preparation. A negligible valence band discontinuity, corresponding to a ∼5.6 eV barrier for electron transport at the BST/Al₂O₃ interface is determined. Current-voltage measurements show that the leakage current can be significantly reduced by inserting the Al₂O₃ barrier layer between barium strontium titanate (BST) and Pt electrode. Different charge injection behavior depending on Al₂O₃ thickness is observed, which correspond well with the experimentally determined energy band diagrams. Direct tunneling from the metal electrode into the BST conduction band through the Al₂O₃ barrier layer is observed.

The interface formation between Ba₀.₆Sr₀.₄TiO₃ and Al₂O₃ has been studied using photoelectron spectroscopy with in situ sample preparation. A negligible valence band discontinuity, corresponding to a ∼5.6 eV barrier for electron transport at the BST/Al₂O₃ interface is determined. Current-voltage measurements show that the leakage current can be significantly reduced by inserting the Al₂O₃ barrier layer between barium strontium titanate (BST) and Pt electrode. Different charge injection behavior depending on Al₂O₃ thickness is observed, which correspond well with the experimentally determined energy band diagrams. Direct tunneling from the metal electrode into the BST conduction band through the Al₂O₃ barrier layer is observed.

In der vorliegenden Arbeit wurden die Grenzflächeneigenschaften steuerbarer Kondensatoren auf Basis kathodenzerstäubter Bariumstrontiumtitanat (BST)-Dünnschichten, die als Schlüsselkomponenten zum Aufbau neuartiger passiver Hochfrequenzschaltungen und Systeme in moderner Mikrowellentechnik dienen, modifiziert und umfassend untersucht. Der zentrale Schwerpunkt dieser Arbeit liegt auf der Korrelation von Grenzflächen-, elektrischen und dielektrischen Eigenschaften. Zur Grenzflächenmodifizierung wurden hoch isolierende Aluminiumoxid-Zwischenschichten bzw. transparente leitfähige Zinn-dotierte Indiumoxid (ITO)-Elektroden eingesetzt. Die Untersuchung der Grenzflächenausbildung, d. h. der Bandanpassung und der Barrierenhöhe zwischen BST und Aluminiumoxid bzw. ITO, erfolgte mittels in situ Photoelektronenspektroskopie. Basierend auf einer Parallelplattenstruktur wurden die elektrischen und dielektrischen Eigenschaften der BST-Kondensatoren im Hinblick auf die durch die Grenzflächenmodifizierung veränderte Ladungsträgerinjektion charakterisiert. Ausgeprägte Strom-Spannungs-Charakteristiken wurden beobachtet und auf unterschiedliche Injektionsmechanismen zurückgeführt. Das dadurch gewonnene Verständnis über die Einflüsse der Grenzflächen wurde in dieser Arbeit für die Modifizierung bzw. Verbesserung der dielektrischen Eigenschaften ausgenutzt, zum Beispiel für die Erhöhung des Gütefaktors oder die Entwicklung neuer Funktionalitäten. Es konnte gezeigt werden, dass die elektronische Struktur der Materialien und deren Grenzflächen eine entscheidende Rolle für die Eigenschaften der Dünnschicht-Bauteile spielen.

In der vorliegenden Arbeit wurden die Grenzflächeneigenschaften steuerbarer Kondensatoren auf Basis kathodenzerstäubter Bariumstrontiumtitanat (BST)-Dünnschichten, die als Schlüsselkomponenten zum Aufbau neuartiger passiver Hochfrequenzschaltungen und Systeme in moderner Mikrowellentechnik dienen, modifiziert und umfassend untersucht. Der zentrale Schwerpunkt dieser Arbeit liegt auf der Korrelation von Grenzflächen-, elektrischen und dielektrischen Eigenschaften. Zur Grenzflächenmodifizierung wurden hoch isolierende Aluminiumoxid-Zwischenschichten bzw. transparente leitfähige Zinn-dotierte Indiumoxid (ITO)-Elektroden eingesetzt. Die Untersuchung der Grenzflächenausbildung, d. h. der Bandanpassung und der Barrierenhöhe zwischen BST und Aluminiumoxid bzw. ITO, erfolgte mittels in situ Photoelektronenspektroskopie. Basierend auf einer Parallelplattenstruktur wurden die elektrischen und dielektrischen Eigenschaften der BST-Kondensatoren im Hinblick auf die durch die Grenzflächenmodifizierung veränderte Ladungsträgerinjektion charakterisiert. Ausgeprägte Strom-Spannungs-Charakteristiken wurden beobachtet und auf unterschiedliche Injektionsmechanismen zurückgeführt. Das dadurch gewonnene Verständnis über die Einflüsse der Grenzflächen wurde in dieser Arbeit für die Modifizierung bzw. Verbesserung der dielektrischen Eigenschaften ausgenutzt, zum Beispiel für die Erhöhung des Gütefaktors oder die Entwicklung neuer Funktionalitäten. Es konnte gezeigt werden, dass die elektronische Struktur der Materialien und deren Grenzflächen eine entscheidende Rolle für die Eigenschaften der Dünnschicht-Bauteile spielen.

In der vorliegenden Arbeit wurden die Grenzflächeneigenschaften steuerbarer Kondensatoren auf Basis kathodenzerstäubter Bariumstrontiumtitanat (BST)-Dünnschichten, die als Schlüsselkomponenten zum Aufbau neuartiger passiver Hochfrequenzschaltungen und Systeme in moderner Mikrowellentechnik dienen, modifiziert und umfassend untersucht. Der zentrale Schwerpunkt dieser Arbeit liegt auf der Korrelation von Grenzflächen-, elektrischen und dielektrischen Eigenschaften. Zur Grenzflächenmodifizierung wurden hoch isolierende Aluminiumoxid-Zwischenschichten bzw. transparente leitfähige Zinn-dotierte Indiumoxid (ITO)-Elektroden eingesetzt. Die Untersuchung der Grenzflächenausbildung, d. h. der Bandanpassung und der Barrierenhöhe zwischen BST und Aluminiumoxid bzw. ITO, erfolgte mittels in situ Photoelektronenspektroskopie. Basierend auf einer Parallelplattenstruktur wurden die elektrischen und dielektrischen Eigenschaften der BST-Kondensatoren im Hinblick auf die durch die Grenzflächenmodifizierung veränderte Ladungsträgerinjektion charakterisiert. Ausgeprägte Strom-Spannungs-Charakteristiken wurden beobachtet und auf unterschiedliche Injektionsmechanismen zurückgeführt. Das dadurch gewonnene Verständnis über die Einflüsse der Grenzflächen wurde in dieser Arbeit für die Modifizierung bzw. Verbesserung der dielektrischen Eigenschaften ausgenutzt, zum Beispiel für die Erhöhung des Gütefaktors oder die Entwicklung neuer Funktionalitäten. Es konnte gezeigt werden, dass die elektronische Struktur der Materialien und deren Grenzflächen eine entscheidende Rolle für die Eigenschaften der Dünnschicht-Bauteile spielen.

In der vorliegenden Arbeit wurden die Grenzflächeneigenschaften steuerbarer Kondensatoren auf Basis kathodenzerstäubter Bariumstrontiumtitanat (BST)-Dünnschichten, die als Schlüsselkomponenten zum Aufbau neuartiger passiver Hochfrequenzschaltungen und Systeme in moderner Mikrowellentechnik dienen, modifiziert und umfassend untersucht. Der zentrale Schwerpunkt dieser Arbeit liegt auf der Korrelation von Grenzflächen-, elektrischen und dielektrischen Eigenschaften. Zur Grenzflächenmodifizierung wurden hoch isolierende Aluminiumoxid-Zwischenschichten bzw. transparente leitfähige Zinn-dotierte Indiumoxid (ITO)-Elektroden eingesetzt. Die Untersuchung der Grenzflächenausbildung, d. h. der Bandanpassung und der Barrierenhöhe zwischen BST und Aluminiumoxid bzw. ITO, erfolgte mittels in situ Photoelektronenspektroskopie. Basierend auf einer Parallelplattenstruktur wurden die elektrischen und dielektrischen Eigenschaften der BST-Kondensatoren im Hinblick auf die durch die Grenzflächenmodifizierung veränderte Ladungsträgerinjektion charakterisiert. Ausgeprägte Strom-Spannungs-Charakteristiken wurden beobachtet und auf unterschiedliche Injektionsmechanismen zurückgeführt. Das dadurch gewonnene Verständnis über die Einflüsse der Grenzflächen wurde in dieser Arbeit für die Modifizierung bzw. Verbesserung der dielektrischen Eigenschaften ausgenutzt, zum Beispiel für die Erhöhung des Gütefaktors oder die Entwicklung neuer Funktionalitäten. Es konnte gezeigt werden, dass die elektronische Struktur der Materialien und deren Grenzflächen eine entscheidende Rolle für die Eigenschaften der Dünnschicht-Bauteile spielen.

In der vorliegenden Arbeit wurden die Grenzflächeneigenschaften steuerbarer Kondensatoren auf Basis kathodenzerstäubter Bariumstrontiumtitanat (BST)-Dünnschichten, die als Schlüsselkomponenten zum Aufbau neuartiger passiver Hochfrequenzschaltungen und Systeme in moderner Mikrowellentechnik dienen, modifiziert und umfassend untersucht. Der zentrale Schwerpunkt dieser Arbeit liegt auf der Korrelation von Grenzflächen-, elektrischen und dielektrischen Eigenschaften. Zur Grenzflächenmodifizierung wurden hoch isolierende Aluminiumoxid-Zwischenschichten bzw. transparente leitfähige Zinn-dotierte Indiumoxid (ITO)-Elektroden eingesetzt. Die Untersuchung der Grenzflächenausbildung, d. h. der Bandanpassung und der Barrierenhöhe zwischen BST und Aluminiumoxid bzw. ITO, erfolgte mittels in situ Photoelektronenspektroskopie. Basierend auf einer Parallelplattenstruktur wurden die elektrischen und dielektrischen Eigenschaften der BST-Kondensatoren im Hinblick auf die durch die Grenzflächenmodifizierung veränderte Ladungsträgerinjektion charakterisiert. Ausgeprägte Strom-Spannungs-Charakteristiken wurden beobachtet und auf unterschiedliche Injektionsmechanismen zurückgeführt. Das dadurch gewonnene Verständnis über die Einflüsse der Grenzflächen wurde in dieser Arbeit für die Modifizierung bzw. Verbesserung der dielektrischen Eigenschaften ausgenutzt, zum Beispiel für die Erhöhung des Gütefaktors oder die Entwicklung neuer Funktionalitäten. Es konnte gezeigt werden, dass die elektronische Struktur der Materialien und deren Grenzflächen eine entscheidende Rolle für die Eigenschaften der Dünnschicht-Bauteile spielen.

In der vorliegenden Arbeit wurden die Grenzflächeneigenschaften steuerbarer Kondensatoren auf Basis kathodenzerstäubter Bariumstrontiumtitanat (BST)-Dünnschichten, die als Schlüsselkomponenten zum Aufbau neuartiger passiver Hochfrequenzschaltungen und Systeme in moderner Mikrowellentechnik dienen, modifiziert und umfassend untersucht. Der zentrale Schwerpunkt dieser Arbeit liegt auf der Korrelation von Grenzflächen-, elektrischen und dielektrischen Eigenschaften. Zur Grenzflächenmodifizierung wurden hoch isolierende Aluminiumoxid-Zwischenschichten bzw. transparente leitfähige Zinn-dotierte Indiumoxid (ITO)-Elektroden eingesetzt. Die Untersuchung der Grenzflächenausbildung, d. h. der Bandanpassung und der Barrierenhöhe zwischen BST und Aluminiumoxid bzw. ITO, erfolgte mittels in situ Photoelektronenspektroskopie. Basierend auf einer Parallelplattenstruktur wurden die elektrischen und dielektrischen Eigenschaften der BST-Kondensatoren im Hinblick auf die durch die Grenzflächenmodifizierung veränderte Ladungsträgerinjektion charakterisiert. Ausgeprägte Strom-Spannungs-Charakteristiken wurden beobachtet und auf unterschiedliche Injektionsmechanismen zurückgeführt. Das dadurch gewonnene Verständnis über die Einflüsse der Grenzflächen wurde in dieser Arbeit für die Modifizierung bzw. Verbesserung der dielektrischen Eigenschaften ausgenutzt, zum Beispiel für die Erhöhung des Gütefaktors oder die Entwicklung neuer Funktionalitäten. Es konnte gezeigt werden, dass die elektronische Struktur der Materialien und deren Grenzflächen eine entscheidende Rolle für die Eigenschaften der Dünnschicht-Bauteile spielen.