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Surface Science @ Universidad Autónoma de Madrid Roberto Otero On behalf of all the members of the Surface Science Laboratory @ Universidad Autónoma de Madrid
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Nanosciences & Surface Science Optical devices based on organic thin films Nanomechanical biosensors Molecular electronic devices Functionalized surfaces for implant applications Introduction
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Organic Optoelectronic Devices Example: Pentacene thin films Intensity (a.u.) 2θ (º) C. D. Dimitrakopoulos & P. L. Malefant, Advanced Materials 14, 99 (2002) Introduction
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Thin Film Growth Introduction For organic adsorbates : -3D molecular structure (degrees of freedom) -Specificity in intermolecular interactions
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Ultra-High Vacuum (UHV) How long does it take for an atomically clean single-crystal surface to get dirty? Nº of incident molecules/time × area = At RT, P = 1 Atm, m = 4 uma, about 7.71 × 10 27 molecules per second and square meter hit the surface. For Cu (100) (square lattice with lattice parameter 2.56 Å) this number equals 5 × 10 9 molecules/second and unit cell At P = 10 -10 Torr, only 6 × 10 -4 molecules per second and unit cell hit the surface, i.e. an average of 25 min are necessary to have all the unit cells hit by one molecule Introduction
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Ultra-High Vacuum (UHV) Introduction
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Ultra-High Vacuum (UHV) Introduction 20 × 20 nm 2 O/Cu(110) P O = 10 -8 Torr t frame = 20 s
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Experimental Techniques Introduction Structure: –Real Space (STM) –Reciprocal Space (SXRD, TEAS) Chemistry (XPS) Electronic Structure (UPS, STS) Other properties… magnetism? (SP- STM, SMOKE)
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Scanning Tunneling Microscopy and Spectroscopy
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Scanning Tunneling Microscopy (STM) STM
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Things to do in the lab when you have an STM… STM Atomic structure of solid surfaces with vertical pm resolution Morphology of epitaxial systems Subnanometer- resolution electronic spectroscopy Diffusion of atomic adsorbates Atom-by- atom nanostructure fabrication
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TIREMISU (TIme REsolved MIcroscopy of SUrfaces) STM José María Gallego Me David Écija Christian Urban Marta Trelka
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SITTA (Sistema Integral de Túnel y Técnicas de Análisis) STM Fabián Calleja Juan José Hinarejos Amadeo L. Vázquez de Parga
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STM/STS: Layer-Dependent Roughening Transition F. Calleja, M. C. G. Passeggi, Jr., J. J. Hinarejos, A. L. Vázquez de Parga, and R. Miranda, Phys. Rev. Lett. 97, 186104 (2006) STM
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Diffraction and the Reciprocal Space
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Elementary Diffraction Theory Reciprocal space vector Wavelength ≈ Lattice parameter Diffraction
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X-Rays: SXRD λ ≈ 1 Å, E ≈ 12.3 keV → X Rays Large penetration depth!!! Real SpaceReciprocal Space Diffraction
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Baby Chambers at Synchrotrons Diffraction Jesús ÁlvarezMaría José Capitán Me Hamburg
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Adenine Self-Assembly Diffraction
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Molecule Diffraction from Surfaces Diffraction
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The Atomic and Molecular Beam Diffraction Apparatus at LASUAM Diffraction Guillaume Laurent Daniel Farías Daniel Barredo Pablo Nieto
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H 2 Diffraction In-plane and out-of-plane H 2 diffraction spectra from Pt(111) recorded along the two main azimuths: P. Nieto, E. Pijper, D. Barredo, G. Laurent, R.A. Olsen, E.J. Baerends, G.J. Kroes and D. Farías, Science 312, 86 (2006) Diffraction
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Surface Phonons Diffraction Phonons on Pd(110):
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Chemical and Electronic Characterization
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Electrons in Solid Spectroscopy
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XRPS Cristina Navío Jesús Álvarez María José Capitán Spectroscopy
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X-Ray and UV Photoelectron Spectroscopy (XPS) Spectroscopy 3000 Å x 3000 Å N 1s Fe 2p Fe 4 N stoichiometry
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Other Techniques
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SMOKE (Surface Magneto-Optical Kerr Effect) Dr. Julio Camarero HeNe laser polarizer lens Wollaston prism analyser DSO Field servo-loop-control power supply FREQ FIELD fast photodiodes + – Hall signal lens air gap ferrite /2 plate 1 current sensor Magnetism
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Spin-Polarized STM SampleTip MsMs MTMT Φ EFEF EFEF High current Amadeo L. Vázquez de Parga Magnetism
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Sample: Mn/Fe(001) Mn grown at 370 K (<4x10 -10 mbar) STM image after depositing 7 ML 140 x 150 nm 2 V s = - 0.5 V I=0.5 nA 6 7 8 9 9 9 8 8 0.16 nm 0.14 nm Fe(001)-whisker Mn(001) film 6 7 8 9 9 9 8 8 dI/dV curves dI/dV map at +0.2 V STS measured with clean W tip Spin-Polarized STM Magnetism
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8 9 10 100 x 100 nm 2 V s = - 0.5V, I=0.5nA 10 11 12 Sample voltage [V] -0.50.00.5 1.0 dI/dV [nA/V] 0.5 1.5 2.5 8 9 10 11 dI/dV map at +0.2 V 8 9 10 11 10 9 STM image With the Fe-coated W tip alternating contrast with a clean W tip there is no contrast Reversed contrast with different Fe-coated W tips due to different tip magnetization 9 12 dI/dV curves STS measured at room temperature with Fe-coated W tip 100 x 100 nm 2 Spin-Polarized STM Magnetism
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80 x 80 nm 2 I map at V=0.10 V 6.5 ML of Mn/Fe(001) Topography Measured at room temperature Spin-Polarized STM Magnetism
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Conclusion A multitechnique approach to address problems related with the growth and characterization of nanostructures
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