The Experts below are selected from a list of 28440 Experts worldwide ranked by ideXlab platform
Horst Rogalla - One of the best experts on this subject based on the ideXlab platform.
-
Surface morphology determined by 001 singel crystal srtio3 termination
Physica C-superconductivity and Its Applications, 2000Co-Authors: Gertjan Koster, Guus Rijnders, Dave H A Blank, Horst RogallaAbstract:The terminating layer of a perovskite (0 0 1) ABO3 crystal, with A as an alkaline earth metal and B as a transition metal, influences the characteristics of the Surface. The morphology during thermal treatment of the Surface and epitaxial growth are determined by the composition of the Surface, i.e., whether it is BO2, AO, or a mixed-Terminated Surface. Since the morphology of a thin film is the result of the evolution of the Surface during deposition, control from the very first layer is essential for smooth films. In the case of perovskite materials, this means control of the terminating layer. Here, we study the SrTiO3 Surface as a model system and the effects of the composition of the terminating layer, determined by the treatment and/or deposition of SrO and TiO2, on homo-epitaxial and hetero-epitaxial growth of SrCuO2 and YBa2Cu3O7. A single-Terminated Surface turns out to be optimal with respect to a smooth morphology and perfect epitaxy of high-Tc superconducting materials.
-
quasi ideal strontium titanate crystal Surfaces through formation of stontium hydroxide
Applied Physics Letters, 1998Co-Authors: Gertjan Koster, Guus Rijnders, Dave H A Blank, B L Kropman, Horst RogallaAbstract:In recent years, well-defined and nearly perfect single crystal Surfaces of oxide perovskites have become increasingly important. A single Terminated Surface is a prerequisite for reproducible thin film growth and fundamental growth studies. In this work, atomic and lateral force microscopy have been used to display different terminations of SrTiO3. We observe hydroxylation of the topmost SrO layer after immersion of SrTiO3 in water, which is used to enhance the etch-selectivity of SrO relative to TiO2 in a buffered HF solution. We reproducibly obtain perfect and single Terminated Surfaces, irrespective of the initial state of polished Surfaces and the pH value of the HF solution. This approach to the problem might be used for a variety of multi-component oxide single crystals. True two-dimensional reflection high-energy electron diffraction intensity oscillations are observed during homo epitaxial growth using pulsed laser deposition on these Surfaces.
-
quasi ideal strontium titanate crystal Surfaces through formation of strontium hydroxide
Applied Physics Letters, 1998Co-Authors: Gertjan Koster, Guus Rijnders, Dave H A Blank, B L Kropman, Horst RogallaAbstract:In recent years, well-defined and nearly perfect single crystal Surfaces of oxide perovskites have become increasingly important. A single Terminated Surface is a prerequisite for reproducible thin film growth and fundamental growth studies. In this work, atomic and lateral force microscopy have been used to display different terminations of SrTiO3. We observe hydroxylation of the topmost SrO layer after immersion of SrTiO3 in water, which is used to enhance the etch-selectivity of SrO relative to TiO2 in a buffered HF solution. We reproducibly obtain perfect and single Terminated Surfaces, irrespective of the initial state of polished Surfaces and the pH value of the HF solution. This approach to the problem might be used for a variety of multi-component oxide single crystals. True two-dimensional reflection high-energy electron diffraction intensity oscillations are observed during homo epitaxial growth using pulsed laser deposition on these Surfaces.
Hansjoachim Freund - One of the best experts on this subject based on the ideXlab platform.
-
ferryl fe o termination of the hematite α fe2o3 0001 Surface
Physical Review Letters, 2005Co-Authors: Celine Lemire, Serena Bertarione, Adriano Zecchina, Domenica Scarano, Anne M Chaka, Shamil K Shaikhutdinov, Hansjoachim FreundAbstract:Using scanning tunneling microscopy and infrared reflection absorption spectroscopy we have observed that the alpha-Fe2O3(0001) Surface exhibits ferryl (Fe=O) groups, which may coexist with domains of the Fe-Terminated Surface. We therefore fully support ab initio calculations recently reported in the literature [W. Bergmeyer, H. Schweiger, and E. Wimmer, Phys. Rev. B 69, 195409 (2004)]. The close similarity to the results on the (0001) Surfaces of Cr2O3 and V2O3 strongly suggests that the M=O termination under certain oxygen pressure conditions is the most stable for the close-packed Surfaces of transition metal oxides with the corundum structure.
-
ferryl fe o termination of the hematite α fe2o3 0001 Surface
Physical Review Letters, 2005Co-Authors: Celine Lemire, Serena Bertarione, Adriano Zecchina, Domenica Scarano, Anne M Chaka, Shamil K Shaikhutdinov, Hansjoachim FreundAbstract:Using scanning tunneling microscopy and infrared reflection absorption spectroscopy we have observed that the $\ensuremath{\alpha}\mathrm{\text{\ensuremath{-}}}\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{3}(0001)$ Surface exhibits ferryl ($\mathrm{Fe}\mathrm{O}$) groups, which may coexist with domains of the Fe-Terminated Surface. We therefore fully support ab initio calculations recently reported in the literature [W. Bergmeyer, H. Schweiger, and E. Wimmer, Phys. Rev. B 69, 195409 (2004)]. The close similarity to the results on the (0001) Surfaces of $\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ strongly suggests that the $M\mathrm{O}$ termination under certain oxygen pressure conditions is the most stable for the close-packed Surfaces of transition metal oxides with the corundum structure.
Gertjan Koster - One of the best experts on this subject based on the ideXlab platform.
-
Surface morphology determined by 001 singel crystal srtio3 termination
Physica C-superconductivity and Its Applications, 2000Co-Authors: Gertjan Koster, Guus Rijnders, Dave H A Blank, Horst RogallaAbstract:The terminating layer of a perovskite (0 0 1) ABO3 crystal, with A as an alkaline earth metal and B as a transition metal, influences the characteristics of the Surface. The morphology during thermal treatment of the Surface and epitaxial growth are determined by the composition of the Surface, i.e., whether it is BO2, AO, or a mixed-Terminated Surface. Since the morphology of a thin film is the result of the evolution of the Surface during deposition, control from the very first layer is essential for smooth films. In the case of perovskite materials, this means control of the terminating layer. Here, we study the SrTiO3 Surface as a model system and the effects of the composition of the terminating layer, determined by the treatment and/or deposition of SrO and TiO2, on homo-epitaxial and hetero-epitaxial growth of SrCuO2 and YBa2Cu3O7. A single-Terminated Surface turns out to be optimal with respect to a smooth morphology and perfect epitaxy of high-Tc superconducting materials.
-
quasi ideal strontium titanate crystal Surfaces through formation of stontium hydroxide
Applied Physics Letters, 1998Co-Authors: Gertjan Koster, Guus Rijnders, Dave H A Blank, B L Kropman, Horst RogallaAbstract:In recent years, well-defined and nearly perfect single crystal Surfaces of oxide perovskites have become increasingly important. A single Terminated Surface is a prerequisite for reproducible thin film growth and fundamental growth studies. In this work, atomic and lateral force microscopy have been used to display different terminations of SrTiO3. We observe hydroxylation of the topmost SrO layer after immersion of SrTiO3 in water, which is used to enhance the etch-selectivity of SrO relative to TiO2 in a buffered HF solution. We reproducibly obtain perfect and single Terminated Surfaces, irrespective of the initial state of polished Surfaces and the pH value of the HF solution. This approach to the problem might be used for a variety of multi-component oxide single crystals. True two-dimensional reflection high-energy electron diffraction intensity oscillations are observed during homo epitaxial growth using pulsed laser deposition on these Surfaces.
-
quasi ideal strontium titanate crystal Surfaces through formation of strontium hydroxide
Applied Physics Letters, 1998Co-Authors: Gertjan Koster, Guus Rijnders, Dave H A Blank, B L Kropman, Horst RogallaAbstract:In recent years, well-defined and nearly perfect single crystal Surfaces of oxide perovskites have become increasingly important. A single Terminated Surface is a prerequisite for reproducible thin film growth and fundamental growth studies. In this work, atomic and lateral force microscopy have been used to display different terminations of SrTiO3. We observe hydroxylation of the topmost SrO layer after immersion of SrTiO3 in water, which is used to enhance the etch-selectivity of SrO relative to TiO2 in a buffered HF solution. We reproducibly obtain perfect and single Terminated Surfaces, irrespective of the initial state of polished Surfaces and the pH value of the HF solution. This approach to the problem might be used for a variety of multi-component oxide single crystals. True two-dimensional reflection high-energy electron diffraction intensity oscillations are observed during homo epitaxial growth using pulsed laser deposition on these Surfaces.
Seiji Takeda - One of the best experts on this subject based on the ideXlab platform.
-
silicon nanowhiskers grown on a hydrogen Terminated silicon 111 Surface
Applied Physics Letters, 1998Co-Authors: Nobuhiko Ozaki, Yutaka Ohno, Seiji TakedaAbstract:Using a hydrogen-Terminated Si {111} Surface as a substrate, we have grown Si nanowhiskers along the 〈112〉 direction by the vapor–liquid–solid mechanism. The minimum silicon core diameter was 3 nm and the maximum length was about 2 μm. The minimum silicon core diameter is close to the critical value for visible light emission due to the quantum confinement effect. In contrast to an oxidized Si Surface, the hydrogen-Terminated Surface facilitates the formation of small molten Au–Si catalysts at a lower temperature (500 °C) which is slightly above the eutectic temperature. The formation of catalysts and the subsequent growth at the low temperature yield thin Si nanowhiskers on a Si substrate.
Anne M Chaka - One of the best experts on this subject based on the ideXlab platform.
-
ferryl fe o termination of the hematite α fe2o3 0001 Surface
Physical Review Letters, 2005Co-Authors: Celine Lemire, Serena Bertarione, Adriano Zecchina, Domenica Scarano, Anne M Chaka, Shamil K Shaikhutdinov, Hansjoachim FreundAbstract:Using scanning tunneling microscopy and infrared reflection absorption spectroscopy we have observed that the alpha-Fe2O3(0001) Surface exhibits ferryl (Fe=O) groups, which may coexist with domains of the Fe-Terminated Surface. We therefore fully support ab initio calculations recently reported in the literature [W. Bergmeyer, H. Schweiger, and E. Wimmer, Phys. Rev. B 69, 195409 (2004)]. The close similarity to the results on the (0001) Surfaces of Cr2O3 and V2O3 strongly suggests that the M=O termination under certain oxygen pressure conditions is the most stable for the close-packed Surfaces of transition metal oxides with the corundum structure.
-
ferryl fe o termination of the hematite α fe2o3 0001 Surface
Physical Review Letters, 2005Co-Authors: Celine Lemire, Serena Bertarione, Adriano Zecchina, Domenica Scarano, Anne M Chaka, Shamil K Shaikhutdinov, Hansjoachim FreundAbstract:Using scanning tunneling microscopy and infrared reflection absorption spectroscopy we have observed that the $\ensuremath{\alpha}\mathrm{\text{\ensuremath{-}}}\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{3}(0001)$ Surface exhibits ferryl ($\mathrm{Fe}\mathrm{O}$) groups, which may coexist with domains of the Fe-Terminated Surface. We therefore fully support ab initio calculations recently reported in the literature [W. Bergmeyer, H. Schweiger, and E. Wimmer, Phys. Rev. B 69, 195409 (2004)]. The close similarity to the results on the (0001) Surfaces of $\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ strongly suggests that the $M\mathrm{O}$ termination under certain oxygen pressure conditions is the most stable for the close-packed Surfaces of transition metal oxides with the corundum structure.
-
effect of the environment on alpha al2o3 0001 Surface structures
Physical Review Letters, 2000Co-Authors: Xiaogang Wang, Anne M Chaka, Matthias SchefflerAbstract:We report that calculating the Gibbs free energy of the alpha-Al2O3 (0001) Surfaces in equilibrium with a realistic environment containing both oxygen and hydrogen species is essential for obtaining theoretical predictions consistent with experimental observations. Using density-functional theory we find that even under conditions of high oxygen partial pressure the metal-Terminated Surface is surprisingly stable. An oxygen-Terminated alpha-Al2O3 (0001) Surface becomes stable only if hydrogen is present on the Surface. In addition, including hydrogen on the Surface resolves discrepancies between previous theoretical work and experimental results with respect to the magnitude and direction of Surface relaxations.
