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1.
A class of nanostructured surface phases on SrTiO3(001) is reported and characterized through atomic-resolution scanning tunneling microscopy and Auger electron spectroscopy. These surface phases are created via argon ion sputtering and UHV annealing and form close-packed domains of highly ordered nanostructures. Depending on the type of nanostructures present, the domain ordering exhibit either (6 x 2), (9 x 2), (12 x 2), (6 x 8), or (7 x 4) surface patterning. The nanostructures are composed of TiO2-derived complexes surrounded by a TiO2 surface termination. Such surface ordering phenomena introduce another level of complexity in the chemistry of perovskite oxide surfaces and provide a basis from which potential photocatalytic and molecular-ordering applications may be developed. 相似文献
2.
Surface structures of defective SrTiO(3) (001) have been studied by using scanning probe microscopy and density functional theory calculations. We observed several defective surface structures with true atomic resolution under reducing ultrahigh vacuum conditions. It is found that all the defects are terminated by (001), (100) and (010) microfacets of the TiO(2) plane. We propose microfaceting TiO(2) termination with Sr adatom models. The formation of various types of defects is driven by the changes of the surface stoichiometry depending on surface preparations. 相似文献
3.
Radović M Salluzzo M Ristić Z Di Capua R Lampis N Vaglio R Miletto Granozio F 《The Journal of chemical physics》2011,135(3):034705
We report on a systematic study of the growth of epitaxial TiO(2) films deposited by pulsed laser deposition on Ti-terminated SrTiO(3) (001) single crystals. By using in situ reflection high energy electron diffraction, low energy electron diffraction, x-ray photoemission spectroscopy, and scanning probe microscopy, we show that the stabilization of the anatase (001) phase is preceded by the growth of a few nanometers thick pseudomorphic Sr(x)TiO(2+y) (x, y < 1) intermediate layer. The data demonstrate that the formation of this intermediate phase is related to the activation of a long range Sr migration from the SrTiO(3) substrate into the film. Our results enrich the phase diagram of the Sr-Ti-O system under epitaxial strain opening a route for the study of the electronic and dielectric properties of the reported Sr-deficient SrTiO(3) phase. 相似文献
4.
5.
Surface structures of rutile TiO(2) (011) are determined by a combination of noncontact atomic force microscopy (NC-AFM), scanning tunneling microscopy (STM), and density functional calculations. The surface exhibits rowlike (n x 1) structures running along the [01] direction. Microfaceting missing-row structural models can explain the experimental results very well. Calculated images for NC-AFM and STM are in good agreement with the experimental results. A decrease of the density of dangling bonds stabilizes the surface energy, which results in the microfaceting missing-row reconstructions. 相似文献
6.
TiO2是一种优异的光电功能材料,被广泛用于有机污染物光降解及太阳能光电转换[1~3].近年来的研究表明,表面原子排布对TiO2光电效能有决定性的影响.如Lowckamp[3]的研究表明,TiO2的(101)晶面与其它晶面相比具有高的光化学还原Ag+的能力.本文结合偏振光技术与表面光电压谱技术对金红石型TiO2单晶(001)面的光伏响应特性进行了研究,通过对TiO2不同晶面的电子跃迁形式的区分及其对偏振光的不同响应,揭示了表面原子排布与TiO2光电性质之间的关系,实现了对材料功能特性的调控. 相似文献
7.
Winn DL Hale MJ Grassman TJ Sexton JZ Kummel AC Passlack M Droopad R 《The Journal of chemical physics》2007,127(13):134705
A systematic experimental and theoretical study was performed to determine the causes of oxide-induced Fermi level pinning and unpinning on GaAs(001)-c(2 x 8)/(2 x 4). Scanning tunneling spectroscopy (STS) and density functional theory (DFT) were used to study four different adsorbates' (O(2), In(2)O, Ga(2)O, and SiO) bonding to the GaAs(001)-c(2 x 8)/(2 x 4) surface. The STS results revealed that out of the four adsorbates studied, only one left the Fermi level unpinned, Ga(2)O. DFT calculations were used to elucidate the causes of the Fermi level pinning. Two distinct pinning mechanisms were identified: direct (adsorbate induced states in the band gap region) and indirect pinnings (generation of undimerized As atoms). For O(2) dissociative chemisorption onto GaAs(001)-c(2 x 8)/(2 x 4), the Fermi level pinning was only indirect, while direct Fermi level pinning was observed when In(2)O was deposited on GaAs(001)-c(2 x 8)/(2 x 4). In the case of SiO on GaAs(001)-c(2 x 8)/(2 x 4), the Fermi level pinning was a combination of the two mechanisms. 相似文献
8.
TiO2由于其优异的光电性质及高的化学稳定性而受到广泛关注,并且被应用于有机污染物光降解[1]、太阳能光电转换[2]等诸多领域.由于制备方法不同,TiO2往往会呈现出不同的光电性质,尽管其晶型与粒度可能相差甚微[3].近年来研究表明,除晶型、粒度等因素外,表面原子排布在决定材料光电性质方面同样有重要贡献[4,5].本文采用表面光电压谱(SPS)及场诱导表面光电压谱(EFSPS)研究了TiO2单晶(001)面的光伏响应. 相似文献
9.
Riley DJ Jardine AP Alexandrowicz G Hedgeland H Ellis J Allison W 《The Journal of chemical physics》2008,128(15):154712
Measurements of (3)He scattering from the Cu(001)c(2 x 2)CO surface using (3)He spin-echo spectroscopy show a number of selective adsorption resonance features. The features cannot be reproduced by close coupled scattering calculations based on the existing Cu(001)c(2 x 2)CO-He interaction potential. An empirical potential is created by adjusting the shape, depth, and width of the existing potential to improve agreement with the experimental data. 相似文献
10.
Liangliang Liu Prof. Zhu Wang Prof. Chunxu Pan Prof. Wei Xiao Prof. Kyeongjae Cho 《Chemphyschem》2013,14(5):996-1002
The effect of hydrogen on the adsorption and dissociation of the oxygen molecule on a TiO2 anatase (001) surface is studied by first‐principles calculations coupled with the nudged elastic band (NEB) method. Hydrogen adatoms on the surface can increase the absolute value of the adsorption energy of the oxygen molecule. A single H adatom on an anatase (001) surface can lower dramatically the dissociation barrier of the oxygen molecule. The adsorption energy of an O2 molecule is high enough to break the O?O bond. The system energy is lowered after dissociation. If two H adatoms are together on the surface, an oxygen molecule can be also strongly adsorbed, and the adsorption energy is high enough to break the O?O bond. However, the system energy increases after dissociation. Because dissociation of the oxygen molecule on a hydrogenated anatase (001) surface is more efficient, and the oxygen adatoms on the anatase surface can be used to oxidize other adsorbed toxic small gas molecules, hydrogenated anatase is a promising catalyst candidate. 相似文献
11.
Feng Xiong Yan‐Yan Yu Zongfang Wu Guanghui Sun Liangbing Ding Yuekang Jin Prof. Dr. Xue‐Qing Gong Prof. Dr. Weixin Huang 《Angewandte Chemie (International ed. in English)》2016,55(2):623-628
Exploring reactions of methanol on TiO2 surfaces is of great importance in both C1 chemistry and photocatalysis. Reported herein is a combined experimental and theoretical calculation study of methanol adsorption and reaction on a mineral anatase TiO2(001)‐(1×4) surface. The methanol‐to‐dimethyl ether (DME) reaction was unambiguously identified to occur by the dehydration coupling of methoxy species at the fourfold‐coordinated Ti4+ sites (Ti4c), and for the first time confirms the predicted higher reactivity of this facet compared to other reported TiO2 facets. Surface chemistry of methanol on the anatase TiO2(001)‐(1×4) surface is seldom affected by co‐chemisorbed water. These results not only greatly deepen the fundamental understanding of elementary surface reactions of methanol on TiO2 surfaces but also show that TiO2 with a high density of Ti4c sites is a potentially active and selective catalyst for the important methanol‐to‐DME reaction. 相似文献
12.
Rangan S Bournel F Gallet JJ Kubsky S Le Guen K Dufour G Rochet F Sirotti F Piaszenski G Funke R Kneppe M Köhler U 《The journal of physical chemistry. B》2005,109(26):12899-12908
Using a combination of local -- scanning tunneling microscopy -- and spatially integrated, but chemically sensitive probes -- X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy -- we have examined how 3-butenenitrile reacts with the Si(001)-2 x 1 surface at room temperature. Electron spectroscopies indicate three different nitrogen chemical bonds: a Si-C=N-Si bond, a C=C=N cumulative double bond, and a CN moiety datively bonded to a silicon atom. All molecular imprints detected by scanning tunneling microscopy (STM) involve two adjacent silicon dimers in the same row. The three geometries we propose -- a double di-sigma bonding via the CN and the C=C, a cumulative double bond formation associated with alphaC-H bond dissociation, and a di-sigma vinyl bonding plus a CN datively bonded to a silicon atom -- are all compatible with electron spectroscopies and data. Real-time Auger yield kinetic measurements show that the double di-sigma bonding geometry is unstable when exposed to a continuous flux of 3-butenenitrile molecules, as the Si-C=N-Si unit transforms into a CN moiety. A model is proposed to explain this observation. 相似文献
13.
We have performed first-principles calculations on the (001) surface of cubic SrHfO(3) and SrTiO(3) with SrO and BO(2) (B = Ti or Hf) terminations. Surface structure, partial density of states, band structure, and surface energy have been obtained. For the BO(2)-terminated surface, the largest relaxation appears on the second-layer atoms but not on the first-layer ones. The analysis of the structure relaxation parameters reveals that the rumpling of the (001) surface for SrHfO(3) with SrO termination is stronger than that for SrTiO(3). For the HfO(2)-terminated surface of SrHfO(3), the surface state appears near the M point of its band structure. 相似文献
14.
Prof. Dr. Doris Grumelli Tim Wiegmann Dr. Sara Barja Dr. Finn Reikowski Dr. Fouad Maroun Dr. Philippe Allongue Dr. Jan Balajka Prof. Dr. Gareth S. Parkinson Prof. Dr. Ulrike Diebold Prof. Dr. Klaus Kern Prof. Dr. Olaf M. Magnussen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22088-22092
Establishing the atomic-scale structure of metal-oxide surfaces during electrochemical reactions is a key step to modeling this important class of electrocatalysts. Here, we demonstrate that the characteristic (√2×√2)R45° surface reconstruction formed on (001)-oriented magnetite single crystals is maintained after immersion in 0.1 M NaOH at 0.20 V vs. Ag/AgCl and we investigate its dependence on the electrode potential. We follow the evolution of the surface using in situ and operando surface X-ray diffraction from the onset of hydrogen evolution, to potentials deep in the oxygen evolution reaction (OER) regime. The reconstruction remains stable for hours between −0.20 and 0.60 V and, surprisingly, is still present at anodic current densities of up to 10 mA cm−2 and strongly affects the OER kinetics. We attribute this to a stabilization of the Fe3O4 bulk by the reconstructed surface. At more negative potentials, a gradual and largely irreversible lifting of the reconstruction is observed due to the onset of oxide reduction. 相似文献
15.
Atomic-Scale Studies of Fe3O4(001) and TiO2(110) Surfaces Following Immersion in CO2-Acidified Water
Dr. Francesca Mirabella Dr. Jan Balajka Dr. Jiri Pavelec Markus Göbel Florian Kraushofer Prof. Dr. Michael Schmid Prof. Dr. Gareth S. Parkinson Prof. Dr. Ulrike Diebold 《Chemphyschem》2020,21(16):1788-1796
Difficulties associated with the integration of liquids into a UHV environment make surface-science style studies of mineral dissolution particularly challenging. Recently, we developed a novel experimental setup for the UHV-compatible dosing of ultrapure liquid water and studied its interaction with TiO2 and Fe3O4 surfaces. Herein, we describe a simple approach to vary the pH through the partial pressure of CO2 ( ) in the surrounding vacuum chamber and use this to study how these surfaces react to an acidic solution. The TiO2(110) surface is unaffected by the acidic solution, except for a small amount of carbonaceous contamination. The Fe3O4(001)-( × )R45° surface begins to dissolve at a pH 4.0–3.9 ( =0.8–1 bar) and, although it is significantly roughened, the atomic-scale structure of the Fe3O4(001) surface layer remains visible in scanning tunneling microscopy (STM) images. X-ray photoelectron spectroscopy (XPS) reveals that the surface is chemically reduced and contains a significant accumulation of bicarbonate (HCO3−) species. These observations are consistent with Fe(II) being extracted by bicarbonate ions, leading to dissolved iron bicarbonate complexes (Fe(HCO3)2), which precipitate onto the surface when the water evaporates. 相似文献
16.
We studied chemical reactions between ultrathin metal films (Al, Cr, Fe, Mo) and single-crystal oxides (SrTiO3 (100), TiO2 (110)) with X-ray photoelectron spectroscopy (XPS). The work function of the metal and the electron density in the oxide strongly influence the reaction onset temperature (T(RO)), where metal oxidation is first observed, and the rate of metal oxidation at the metal/oxide interfaces. The Fermi levels of the two contacting phases affect both the space charges formed at the interfaces and the diffusion of ionic defects across the interfaces. These processes, which determine metal oxidation kinetics at relatively low temperatures, can be understood in the framework of the Cabrera-Mott theory. The results suggest that the interfacial reactivity is tunable by modifying the Fermi level (E(F)) of both contacting phases. This effect is of great technological importance for a variety of devices with heterophase boundaries. 相似文献
17.
Tetsuya Kawano Hisanori Yamane 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(10):i92-i94
Single crystals of pentamagnesium titanium(IV) tetraoxide bis(borate), Mg5TiO4(BO3)2, were prepared by slow cooling of the melt from 1623 K in air. The crystal is isostructural with the mineral ludwigite (Mg2FeO2BO3). The Mg and Ti atoms are coordinated by six O atoms and the B atom is coordinated by three O atoms. There are three Mg sites and one mixed site statistically occupied by Mg and Ti atoms. Atoms are at the following special positions: 2a (0, 0, 0) and 2d (0, , ) for two Mg atoms, 4g (x, y, 0) for the mixed Ti/Mg site and the BO3 group, and 4h (x, y, ) for a third Mg and two oxide O atoms. MgO6 and (Ti/Mg)O6 octahedra are connected by sharing of edges to form zigzag folding layers along the c axis. Triangular prismatic tunnels are formed between the folding layers by sharing apical O atoms of the MgO6 and (Ti/Mg)O6 octahedra. 相似文献
18.
Dr. Liang Bao Qinyu Bao Dr. Huaiwei Zhang Prof. Dr. Yongjun Yuan 《Chemphyschem》2021,22(21):2168-2171
A feasible tuning method for oxygen vacancies was realized by annealing under 3 atm H2 with (001)-exposed TiO2 nanosheets. The colored TiO2 sample exhibits an excellent N2 photo-fixation rate owing to the abundant oxygen vacancies (OVs) thus demonstrating that annealing with high pressure H2 is exceedingly efficient for tuning surface OVs. 相似文献
19.
Barbora Laskova Marketa Zukalova Ladislav Kavan Alison Chou Paul Liska Zhang Wei Liu Bin Pavel Kubat Elham Ghadiri Jacques E. Moser Michael Gr?tzel 《Journal of Solid State Electrochemistry》2012,16(9):2993-3001
A nanocrystalline TiO2 (anatase) nanosheet exposing mainly the (001) crystal faces was tested as photoanode material in dye-sensitized solar cells. The nanosheets were prepared by hydrothermal growth in HF medium. Good-quality thin films were deposited on F-doped SnO2 support from the TiO2 suspension in ethanolic or aqueous media. The anatase (001) face adsorbs a smaller amount of the used dye sensitizer (C101) per unit area than the (101) face which was tested as a reference. The corresponding solar cell with sensitized (001)-nanosheet photoanode exhibits a larger open-circuit voltage than the reference cell with (101)-terminated anatase nanocrystals. The voltage enhancement is attributed to the negative shift of flatband potential for the (001) face. This conclusion rationalizes earlier works on similar systems, and it indicates that careful control of experimental conditions is needed to extract the effect of band energetic on the current/voltage characteristics of dye-sensitized solar cell. 相似文献
20.
Föhlisch A Wurth W Stichler M Keller C Nilsson A 《The Journal of chemical physics》2004,121(10):4848-4852
The atom specific electronic structure of (2 square root of 3 x 2 square root of 3)R30 degrees CO on hcp Ru(0001) has been determined with resonantly excited x-ray emission spectroscopy. We find that the general features of the local adsorbate electronic structure are similar to the situation of CO adsorbed on the fcc metals Ni(100) and Cu(100). The interpretation of the surface chemical bond of (2 square root of 3 x 2 square root of 3)R30 degrees CO/Ru(0001) based on the direct application of the local, allylic model from on-top adsorption on the fcc(100) surfaces Ni(100) and Cu(100) explains many aspects of the surface chemical bond. However, also nonlocal contributions like adsorbate-adsorbate interaction and the deviation from upright on-top adsorption on the Ru(0001) surface influence observables like the heat of adsorption and the Me-CO bond strength. 相似文献