112 research outputs found
Two-dimensional long-range-ordered growth of uniform cobalt nanostructures on a Au(111) vicinal template
No full textA novel approach based on strain-relief vicinal patterned substrates is demonstrated for two-dimensional (2D) self-ordered growth. Long-range ordered cobalt nanodots growth is achieved using a Au(788) vicinal surface which is spontaneously patterned in two dimensions at a nanometer scale with a macroscopic coherence length. Performing the cobalt growth on a substrate cooled down to 130 K allows a high degree of nanostructure uniformity. The atomic processes responsible for such a behavior are discussed. Such a high quality of both long-range and local ordered cobalt growth opens up the possibility of making measurements of physical properties of such nanostructures by macroscopic integration techniques
Identification and manipulation of defects in black phosphorus
No full textWe identify and manipulate commonly occurring defects in black phosphorus, combining scanning tunneling microscopy experiments with density functional theory calculations. A ubiquitous defect, imaged at negative bias as a bright dumbbell extending over several nanometers, is shown to arise from a substitutional Sn impurity in the second sublayer. Another frequently observed defect type is identified as arising from an interstitial Sn atom; this defect can be switched to a more stable configuration consisting of a Sn substitutional defect + P adatom, by application of an electrical pulse via the STM tip. DFT calculations show that this pulse-induced structural transition switches the system from a non-magnetic configuration to a magnetic one. We introduce States Projected Onto Individual Layers (SPOIL) quantities which provide information about atom-wise and orbital-wise contributions to bias-dependent features observed in STM images.We acknowledge the Indo-French Centre for the Promotion of Advanced Scientific Research (CEFIPRA) for funding our collaboration. We are especially grateful for assistance provided by the Late Ms. A. Sathidevi. We are grateful to the ANR and MOST (DEFINE2D Project No. ANR-20-CE09-0023, MOST 110-2923-M-002-010) for financial support and the TUE-CMS, JNCASR, and the Sheikh Saqr Laboratory, JNCASR, for computational resources. D.S. acknowledges support from the NPDF of the Science and Engineering Research Board (SERB), Government of India.Peer reviewe
Dance in the literary reflection of the early XXth century: a variety of trends
No full textThe paper deals with the role of dance in the Silver Age art world. Maximilian Voloshin is considered to be one of the most outstanding dance metaphysics expounder, and the author focuses on his assessments. The research subjects is two trends in dance and ball culture at the beginning of the XXth century. They are the reform made by an American dancer Icadora Duncan and the repain-ball which conveyed a specific feeling of a person’s freedom. These two trends are connected with appeal to global historical and cultural heritage on its various stages. Paying attention to Voloshin’s literary and critical works the author reveals the importance of personal expound in different periods and its correspondence to the audience’s expectations.Статья посвящена роли танца в художественном мире Серебряного века. Одним из интересных интерпретаторов метафизики танца является Максимилиан Волошин, чьи оценки и суждения находятся в фокусе внимания статьи. Предметом исследования в ней являются две тенденции в танцевальной и бальной культуре начала XX века: реформа американской танцовщицы Айседоры Дункан и балрепэнов, по-своему создавший ощущение свободы человека. Обе они связаны с обращением к всемирному культурно-историческому наследию, его различным эпохам. Обращение к литературно-критическим работам Волошина позволяет обнаружить, насколько важны были субъективные элементы интерпретаций различных эпох и соответствие ожиданиям аудитории
Electronic and structural study of Pt-modified Au vicinal surfaces: a model system for Pt–Au catalysts
No full textFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOTwo single crystalline surfaces of Au vicinal to the (111) plane were modified with Pt and studied using scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) in ultra-high vacuum environment. The vicinal surfaces studied are Au(332) and Au(887) and different Pt coverage (θPt) were deposited on each surface. From STM images we determine that Pt deposits on both surfaces as nanoislands with heights ranging from 1 ML to 3 ML depending on θPt. On both surfaces the early growth of Pt ad-islands occurs at the lower part of the step edge, with Pt ad-atoms being incorporated into the steps in some cases. XPS results indicate that partial alloying of Pt occurs at the interface at room temperature and at all coverage, as suggested by the negative chemical shift of Pt 4f core line, indicating an upward shift of the d-band center of the alloyed Pt. Also, the existence of a segregated Pt phase especially at higher coverage is detected by XPS. Sample annealing indicates that the temperature rise promotes a further incorporation of Pt atoms into the Au substrate as supported by STM and XPS results. Additionally, the catalytic activity of different PtAu systems reported in the literature for some electrochemical reactions is discussed considering our findings. © 2014 The Owner Societies.Two single crystalline surfaces of Au vicinal to the (111) plane were modified with Pt and studied using scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) in ultra-high vacuum environment. The vicinal surfaces studied are Au(332) and Au(887) and different Pt coverage (yPt) were deposited on each surface. From STM images we determine that Pt deposits on both surfaces as nanoislands with heights ranging from 1 ML to 3 ML depending on yPt. On both surfaces the early growth of Pt ad-islands occurs at the lower part of the step edge, with Pt ad-atoms being incorporated into the steps in some cases. XPS results indicate that partial alloying of Pt occurs at the interface at room temperature and at all coverage, as suggested by the negative chemical shift of Pt 4f core line, indicating an upward shift of the d-band center of the alloyed Pt. Also, the existence of a segregated Pt phase especially at higher coverage is detected by XPS. Sample annealing indicates that the temperature rise promotes a further incorporation of Pt atoms into the Au substrate as supported by STM and XPS results. Additionally, the catalytic activity of different PtAu systems reported in the literature for some electrochemical reactions is discussed considering our findings.Two single crystalline surfaces of Au vicinal to the (111) plane were modified with Pt and studied using scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) in ultra-high vacuum environment. The vicinal surfaces studied are Au(332) and Au(887) and different Pt coverage (yPt) were deposited on each surface. From STM images we determine that Pt deposits on both surfaces as nanoislands with heights ranging from 1 ML to 3 ML depending on yPt. On both surfaces the early growth of Pt ad-islands occurs at the lower part of the step edge, with Pt ad-atoms being incorporated into the steps in some cases. XPS results indicate that partial alloying of Pt occurs at the interface at room temperature and at all coverage, as suggested by the negative chemical shift of Pt 4f core line, indicating an upward shift of the d-band center of the alloyed Pt. Also, the existence of a segregated Pt phase especially at higher coverage is detected by XPS. Sample annealing indicates that the temperature rise promotes a further incorporation of Pt atoms into the Au substrate as supported by STM and XPS results. Additionally, the catalytic activity of different PtAu systems reported in the literature for some electrochemical reactions is discussed considering our findings.16261332913339FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO07/54829-5; 2011/12.566-3; 2012/16860-6160172/2011-0Greeley, J., Stephens, I.E.L., Bondarenko, A.S., Johansson, T.P., Hansen, H.A., Jaramillo, T.F., Rossmeisl, J., Nørskov, J.K., (2009) Nat. Chem., 1, pp. 552-556Wu, G., More, K.L., Johnston, C.M., Zelenay, P., (2011) Science, 332, pp. 443-447Chu, Y.H., Shul, Y.G., (2010) Int. J. Hydrogen Energy, 35, pp. 11261-11270Kowal, A., Li, M., Shao, M., Sasaki, K., Vukmirovic, M.B., Zhang, J., Marinkovic, N.S., Adzic, R.R., (2009) Nat. 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Chem., 607, pp. 47-53Kobiela, T., Moors, M., Linhart, W., Cebula, I., Krupski, A., Becker, C., Wandelt, K., (2010) Thin Solid Films, 518, pp. 3650-3657Petkov, V., Wanjala, B.N., Loukrakpam, R., Luo, J., Yang, L., Zhong, C.-J., Shastri, S., (2012) Nano Lett., 12, pp. 4289-4299Authors thank Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP-07/54829-5) and Conselho Nacional de Pesquisa (CNPq) for financial support. Specially thank to L. H. Lima for experimental assistance with STM measurements and Prof. G. Tremiliosi-Filho for lending the Au(332) crystal. MJP, SF and EAC thank FAPESP and CNPq for the fellowships granted (Procs. FAPESP 2011/12.566-3 and 2012/16860-6; Proc. CNPq 160172/2011-0)
Interplay between ordered growth and intermixing of Pt on patterned Au surfaces
No full textInternational audienceWe have investigated the growth of submonolayer coverage of platinum on two gold surfaces (Au(1 1 1) and Au(7 8 8)), at temperatures ranging from 110 K to 300 K. The Scanning Tunneling Microscope images reveal a competition between the ordered growth of nanodots and a random intermixing between Pt and Au. The Pt deposition on the Au(1 1 1) surface at room temperature shows an ordered growth limited by the insertion of Pt atoms into the surface layer and the subsequent modifications of the herringbone surface pattern. In contrast, for Pt on the Au(7 8 8) stepped surface, perfect ordered growth is observed over a wide temperature range. (C) 2010 Elsevier By. All rights reserved
Self-ordering of Au(111) vicinal surfaces and application to nanostructure organized growth
No full textThis paper reports on Au(111) vicinal surfaces, either regularly stepped surfaces, reconstructed or not, or periodically faceted surfaces, which are well suited to be used as templates for organized growth of clusters. Angles of misorientation with respect to the (111) plane lie between 1degrees and 12degrees and two opposite azimuths are considered: (i) [2 (1) over bar(1) over bar], that leads to steps with \100\ microfacets, and (ii) [(2) over bar 11], that leads to steps with \111\ microfacets. The behaviour of the Au(111) reconstruction in the vicinity of steps depends drastically on the step microstructure, and this is a key point for understanding the various periodic morphologies existing on Au(111) vicinal surfaces. The interaction between the reconstruction and the close-packed steps of the Au(111) surface is interpreted in terms of the relative stability of both types of step. Self-organized morphologies between 10 and 100 nm are interpreted within the framework of elastic theory and by pointing out the crucial role played by the atomic boundary energy term. The microscopic origin of faceting is discussed, proposing two different models depending on each azimuth. Then, we illustrate the use of Au(111) vicinal surfaces as templates for growing long range ordered nanostructures. Examples are given in the case of cobalt growth
Reconstruction, step edges and self-organization on the Au(111) surface
No full text5th International Conference on Atomic Controlled Surfaces, Interfaces and Nanostructures (ACSIN 5), UNIV AIX MARSEILLE, AIX PROVENCE, FRANCE, JUL 06-09, 1999It has been shown recently that vicinal surfaces of Au(lll) are unstable towards faceting. The period of the faceted morphology is very sensitive to the step edge atomic structure and can vary from about 10 up to 200 nm. We report a scanning tunneling microscopy (STM) study demonstrating that the famous 22 x root 3 reconstruction of the Au(lll) surface interacts differently with both types of close-packed step edges that can be found on a (111) surface: the lines of discommensuration cross (111) step edges and are stopped by (100) ones. This observation could be essential in order to explain the drastic change in the faceted morphology of Au(111) vicinal surfaces with different step edges. Furthermore, it is promising in the way of realizing original nanostructures on these vicinal surfaces. Preliminary results are shown. (C) 2000 Elsevier Science B.V. All rights reserved
Interaction between steps and reconstruction on Au(111)
No full textDue to its famous 22x root 3 reconstruction, the Au(lll) surface can he considered as an ideal substrate to grow nanostructured arrays of metallic clusters. In this letter, we report a complete investigation of the interaction between this reconstruction and the close-packed steps of the Au(lll) surface. Scanning tunneling microscopy experiments clearly demonstrate that the behaviour of the reconstruction in the vicinity of steps depends drastically on the step microstructure. This result, of particular interest for the managing of new nanostructured substrates, is interpreted in terms of the relative stability of both types of steps
Site selective nucleation on surfaces: the rate equation model compared with VT-STM experiment of Co on Au(788)
No full textHetero-epitaxial growth on patterned surface is a promising way to improve the size distribution of clusters compared to homogeneous growth. Moreover, the use of a self-organized surface provides 2D long range ordered growth such as ordered growth of Co on Au(788). Using variable temperature scanning tunneling microscopy (VT-STM) we have identified an ordered growth regime for a 65-300K temperature range. We compare our experimental results with a rate equation model for the growth on a surface which contains traps. This allows us to explain the different growth behavior versus temperature. In particular, we give an interpretation of the high temperature behavior. Then we discuss the influence of different atomistic mechanisms on the organization. (C) 2004 Elsevier B.V. All rights reserved
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