The first-principles calculations are employed to investigate the electrical properties of polar MgO/BaTiO3（110）interfaces. Both n-type and p-type polar interfaces show a two-dimensional metallic behavior. For the n...The first-principles calculations are employed to investigate the electrical properties of polar MgO/BaTiO3（110）interfaces. Both n-type and p-type polar interfaces show a two-dimensional metallic behavior. For the n-type polar interface,the interface Ti3d electrons are the origin of the metallic and magnetic properties. Varying the thickness of Ba TiO3 may induce an insulator–metal transition, and the critical thickness is 4 unit cells. For the p-type polar interface, holes preferentially occupy the interface O 2p y state, resulting in a conducting interface. The unbalance of the spin splitting of the O 2p states in the interface Mg O layer leads to a magnetic moment of about 0.25μB per O atom at the interface.These results further demonstrate that other polar interfaces, besides LaAlO3/SrTiO3, can show a two-dimensional metallic behavior. It is helpful to fully understand the role of polar discontinuity on the properties of the interface, which widens the field of polar-nonpolar interfaces.展开更多
ZnO thin film growth prefers different orientations on the etched and unetched SrTiO 3（STO）（110） substrates.Inclined ZnO and cobalt-doped ZnO（ZnCoO） thin films are grown on unetched STO（110） substrates using o...ZnO thin film growth prefers different orientations on the etched and unetched SrTiO 3（STO）（110） substrates.Inclined ZnO and cobalt-doped ZnO（ZnCoO） thin films are grown on unetched STO（110） substrates using oxygen plasma assisted molecular beam epitaxy,with the c-axis 42 inclined from the normal STO（110） surface.The growth geometries are ZnCoO[100]//STO[110] and ZnCoO[111]//STO[001].The low temperature photoluminescence spectra of the inclined ZnO and ZnCoO films are dominated by D 0 X emissions associated with A 0 X emissions,and the characteristic emissions for the 2 E（2G）→ 4A2（4F） transition of Co 2＋ dopants and the relevant phonon-participated emissions are observed in the ZnCoO film,indicating the incorporation of Co 2＋ ions at the lattice positions of the Zn 2＋ ions.The c-axis inclined ZnCoO film shows ferromagnetic properties at room temperature.展开更多
为研究亚硝酸(HONO)在γ-Al_(2)O_(3)(110)表面非均相氧化SO_(2)的机理,基于密度泛函理论(density functional theory,DFT)的第一性原理计算了SO_(2)和HONO在γ-Al_(2)O_(3)(110)表面的吸附机制和氧化机制。结果表明,SO_(2)以分子的形...为研究亚硝酸(HONO)在γ-Al_(2)O_(3)(110)表面非均相氧化SO_(2)的机理,基于密度泛函理论(density functional theory,DFT)的第一性原理计算了SO_(2)和HONO在γ-Al_(2)O_(3)(110)表面的吸附机制和氧化机制。结果表明,SO_(2)以分子的形式吸附在完整或缺陷的γ-Al_(2)O_(3)(110)表面,而HONO仅在完整表面上以分子的形式存在。表面氧缺陷的存在不仅会增强SO_(2)和HONO的吸附强度,而且能诱导HONO在含氧缺陷表面的分解(HONO→NO+·OH)。通过局域态密度(partial density of states,PDOS)和Mulliken电荷布局分析表明,HONO的分解遵循Haber-Weiss机制。当SO_(2)和HONO共同吸附在氧缺陷表面时,HONO分解产生·OH,氧化SO_(2)形成HOSO_(2)团簇分子。该研究不仅有助于理解HONO在矿物氧化物表面氧化SO_(2)的作用,而且为解释大气硫酸盐气溶胶的形成提供了理论依据。展开更多
Pure In2O3 is considered as an efficient methanol steam reforming catalyst. Despite of several studies in the past decades, the mechanism of MSR on In2O3 is still not fully understood. In this work, a periodic density...Pure In2O3 is considered as an efficient methanol steam reforming catalyst. Despite of several studies in the past decades, the mechanism of MSR on In2O3 is still not fully understood. In this work, a periodic density functional theory study of the initial dissociation of methanol and water over the In2O3 （110） surface is presented. The activation energy barriers and thermochemistry for several elementary steps are reported. It is found that the energy barri- ers for O--H bond cleavage of both CH3OH and H20 to produce CH30 and OH species at a surface ln-O pair site are very low, indicating that In2O3 （110） can facilely catalyze these two important processes at low temperatures. In addition, the subsequent dehydrogenation of CH30 to CH20 is also found to proceed with a low barrier.展开更多
The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAIO3/SrTiO3 （110）. By comparing their interface energies, it is obta...The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAIO3/SrTiO3 （110）. By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAIO3/SrTiO3 （110） heterostructure, the Ti-O octahedron distortions cause the Ti tzg orbitals to split into the two- fold degenerate dxz/dyz and nondegenerate dxy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaA103 and SrTiO3 leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAIO3/SrTiO3 （110）.展开更多
基金supported by the National Basic Research Program of China(Grant No.2013CB632506)the National Natural Science Foundation of China(Grant Nos.11374186,51231007,51202132,and 51102153)the Independent Innovation Foundation of Shandong University,China(Grant No.2012TS027)
文摘The first-principles calculations are employed to investigate the electrical properties of polar MgO/BaTiO3（110）interfaces. Both n-type and p-type polar interfaces show a two-dimensional metallic behavior. For the n-type polar interface,the interface Ti3d electrons are the origin of the metallic and magnetic properties. Varying the thickness of Ba TiO3 may induce an insulator–metal transition, and the critical thickness is 4 unit cells. For the p-type polar interface, holes preferentially occupy the interface O 2p y state, resulting in a conducting interface. The unbalance of the spin splitting of the O 2p states in the interface Mg O layer leads to a magnetic moment of about 0.25μB per O atom at the interface.These results further demonstrate that other polar interfaces, besides LaAlO3/SrTiO3, can show a two-dimensional metallic behavior. It is helpful to fully understand the role of polar discontinuity on the properties of the interface, which widens the field of polar-nonpolar interfaces.
基金Project supported by the National Basic Research Program of China (Grant No. 2009CB929202)the National Natural ScienceFoundation of China (Grant Nos. 10834001 and 51125004)
文摘ZnO thin film growth prefers different orientations on the etched and unetched SrTiO 3（STO）（110） substrates.Inclined ZnO and cobalt-doped ZnO（ZnCoO） thin films are grown on unetched STO（110） substrates using oxygen plasma assisted molecular beam epitaxy,with the c-axis 42 inclined from the normal STO（110） surface.The growth geometries are ZnCoO[100]//STO[110] and ZnCoO[111]//STO[001].The low temperature photoluminescence spectra of the inclined ZnO and ZnCoO films are dominated by D 0 X emissions associated with A 0 X emissions,and the characteristic emissions for the 2 E（2G）→ 4A2（4F） transition of Co 2＋ dopants and the relevant phonon-participated emissions are observed in the ZnCoO film,indicating the incorporation of Co 2＋ ions at the lattice positions of the Zn 2＋ ions.The c-axis inclined ZnCoO film shows ferromagnetic properties at room temperature.
文摘为研究亚硝酸(HONO)在γ-Al_(2)O_(3)(110)表面非均相氧化SO_(2)的机理,基于密度泛函理论(density functional theory,DFT)的第一性原理计算了SO_(2)和HONO在γ-Al_(2)O_(3)(110)表面的吸附机制和氧化机制。结果表明,SO_(2)以分子的形式吸附在完整或缺陷的γ-Al_(2)O_(3)(110)表面,而HONO仅在完整表面上以分子的形式存在。表面氧缺陷的存在不仅会增强SO_(2)和HONO的吸附强度,而且能诱导HONO在含氧缺陷表面的分解(HONO→NO+·OH)。通过局域态密度(partial density of states,PDOS)和Mulliken电荷布局分析表明,HONO的分解遵循Haber-Weiss机制。当SO_(2)和HONO共同吸附在氧缺陷表面时,HONO分解产生·OH,氧化SO_(2)形成HOSO_(2)团簇分子。该研究不仅有助于理解HONO在矿物氧化物表面氧化SO_(2)的作用,而且为解释大气硫酸盐气溶胶的形成提供了理论依据。
文摘Pure In2O3 is considered as an efficient methanol steam reforming catalyst. Despite of several studies in the past decades, the mechanism of MSR on In2O3 is still not fully understood. In this work, a periodic density functional theory study of the initial dissociation of methanol and water over the In2O3 （110） surface is presented. The activation energy barriers and thermochemistry for several elementary steps are reported. It is found that the energy barri- ers for O--H bond cleavage of both CH3OH and H20 to produce CH30 and OH species at a surface ln-O pair site are very low, indicating that In2O3 （110） can facilely catalyze these two important processes at low temperatures. In addition, the subsequent dehydrogenation of CH30 to CH20 is also found to proceed with a low barrier.
基金Project supported by the National Basis Research Program of China(Grant No.2013CB632506)the National Natural Science Foundation of China(Grant Nos.11374186,51231007,and 51202132)the Independent Innovation Foundation of Shandong University,China(Grant No.2012TS027)
文摘The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAIO3/SrTiO3 （110）. By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAIO3/SrTiO3 （110） heterostructure, the Ti-O octahedron distortions cause the Ti tzg orbitals to split into the two- fold degenerate dxz/dyz and nondegenerate dxy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaA103 and SrTiO3 leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAIO3/SrTiO3 （110）.
