Tunnelspitzen. Vorlesung. Rastersondenmikroskopie WS 2010/11. Spitzenätzung. Themenüberblick. Priv. Doz. Dr. A. Schirmeisen

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1 Vorlesung Rastersondenmikroskopie WS 2010/11 Priv. Doz. Dr. A. Schirmeisen Themenüberblick 0. Einführung 1. Rastertunnelmikroskopie (STM) 2a. Manipulation: Atome verschieben mit dem STM 2b. Reduzierte Dimensionalität: STM und Graphen 3. Rasterkraftmikroskopie (AFM) und intermolekulare Kräfte 4. Reibungskraftmikroskopie (FFM) in der Nanotribologie 5. Dynamisches AFM Topographie und Energie Dissipation 6. Non-contact AFM 3D Kraft-Spektroskopie 7. Nano-Optik: SNOM und TERS Spitzenätzung Tunnelspitzen

2 Spitzenätzung Spitzenanalyse - TEM W tip just after etching, exhibiting oxide layer TEM image indicates clean tip apex after heat treatment annealing Field Ion Microscopy (FIM) Field Ion Microscopy (FIM) Tip radii of 20 A for voltage bias +5 kv UHV for atomic level cleanliness Tip cooled to liquid Nitrogen temperature Electrons tunnel from image gas into tip ions are repelled strongly

3 FIM Image reconstruction Tip Reconstruction FIM image Reconstruction of crystal planes FIM image 3d real space reconstruction FIM - Field Evaporation Imaging : Voltage 4.5 kv Single Atom Tip STM Vom Abbilden zur Manipulation Field Evaporation : Voltage 5.2 kv

4 Fabrikationsstrategien Atomic Manipulation with STM Bottom-Up Atom-Manipulation Self-Assembly Top-Down Lithographie Focussed Ion Beam Moving molecules with the STM tip via electric field between tip and substrate tunneling current interaction forces AG Prof Rieder, FU-Berlin Atomic Manipulation with STM Atomic Manipulation with STM - Manipulation Methods Quantum- Coral Picking-up Method Fe Atome auf Cu(111) Pushing Method (repulsive forces) Pulling Method (attractive forces)

5 Atomic Manipulation with STM - Pushing / Pulling Atomic Manipulation with STM - Pushing / Pulling Cu(211) Oberfläche mit Cu, Pb und Co Adsorbaten Manipulation durch Verschiebung entlag der Stufen. Beispiel: Pb Atom Manipulation durch Verschiebung entlag der Stufen Attraktive Spitze-Atom Wechselwirkung Atomic Manipulation with STM - Pushing / Pulling Atomic Manipulation with STM - Pushing / Pulling Tip height curves during manipulation Example: Complex structures made from CO molecules a) pulling mode, discontinuously b) pulling mode, continuously c) pushing mode Contrast reversal?

6 Chemical Contrast with STM Inducing chemical reactions with STM - Scheme Reaction: Iodobenzene + Copper Catalyst = Biphenyl (Ullmann 1904) Oxygen White arrow: CO transfered to tip STM Manipulation (Scheme): CO Contrast reversed for CO, but not for Oxygen. Here: Tip DOS is important for image contrast! AG Prof Rieder, FU-Berlin Inducing chemical reactions with STM - Experiment Chemical reactions by STM - Diphenyl Two Iodobenzene Molecules Dissociation of one Molecule Iod Molecule moved away Moving of Phenyl Molecules Movement of Diphenyl molecule by pulling along step edge to prove association of molecules Dissociation of the other Molecule Two Phenyl Molecules prepared for association Tip height curves during the manipulation Molecules are moved along the edge of an atomic step of a Copper surface

7 Kondo Effect measured by STM Kondo Effect measured by STM - Elliptic Resonators Free conduction electrons of a metal surface (2d electron sea) are trying to screen a magnetic impurity by counter-aligning their spin This produces a dip in the DOS of the conduction electrons close to E F localized right above the magnetic impurity (Co atom on Cu surface) as measured by STS via di/dv Topography Two ellipitic resonators with their respective focus points Topographic STM images in constant current mode D.Eigler, IBM di/dv at +-5 mv Image of the di/dv spectroscopic signal of the Kondo dip in the DOS Mirage Image of Magnetic Atom Mirage Image of Magnetic Atom Topography of Quantum Corrals with magnetic atom out of focus of ellipse Topography of Quantum Corrals with magnetic atom in one focus of ellipse Image of Kondo signal inside the resonator: no mirage image Image of Kondo signal inside the resonator featuring the mirage image

8 Atomare Schubkarre Atomare Schubkarre HB-HBP Molekül auf Cu(111) Hochheben des Moleküls Cu Atome bleiben liegen Einzelne Cu Atome werden von dem Molekül aufgenommen => Cu Atome unter dem Molekül gefangen Atomare Schubkarre Der kleinste Computer der Welt Höhenprofile des Moleküls mit 1 bis 6 Cu Atomen unter dem Molekül Experiment Theorie CO 2 CO 3 CO Rechnen mit einzelnen Atomen - Kaskadenrechner

9 Der kleinste Computer der Welt Schaltelemente aus einzelnen Molekülen Manipulationsprozess Schaltelemente aus einzelnen Molekülen Der kleinste Computer der Welt Komplexes Schalt-element AND und OR Gatter

10 Der kleinste Computer der Welt 3 Wege Sortierer