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Alternative representation of QW Phase accumulation model

Alternative representation of QW Phase accumulation model

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Alternative representation of QW Phase accumulation model

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  1. Alternative representation of QWPhaseaccumulation model

  2. Dispersion of k(E)

  3. Synchrotron radiation photoemission spectroscopy • ISA Aarhus University • Maximum Energy 580 MeV • Max Current 250 mA • Lifetime 15 hours • SGM1 • 30-400 eV • 1010 photons/sec @130 eV

  4. Photoelectron spectroscopy • Core levels • Chemical reactions/mixing • Growth modes • Valence bands • Electronic levels relevant for optics

  5. Wedge-shaped metal film AFM Sample moved into shadow of shield. Evaporation rate ~1 ML per minute Triangular domains ~200 nm Ag(111) LEED-pattern - only one type of domains Scanning film thickness by moving wedge through laser or synchrotron beam Width of synchrotron beam

  6. Film growth - Si2p spectra Growth at 170 K leads to exponential decay of Si2p levels with ~5Å decay rate. Room temperature annealing of the film leads to growth of large atomically flat domains. Areas with low Ag coverage are formed.  Annealing

  7. Cu buffer layerCu wedge under 10-ML Ag film 3 ML Cu: disordered film 6-7 ML Cu: optimum for Ag overlayer > 7 ML Cu: coupling of overlayer and substrate levels - double peaks - avoided crossings

  8. Effect of Cu buffer layer

  9. QW levels and film roughness 0 -0.5 -1 Binding Energy (eV) -1.5 Beam size on sample ~1 mm -2 -2.5 0 2 4 6 8 10 12 14 16 18 20 22 24 Thickness (ML) Film thickness variations expected within probed area Variations within a few atomic layer give broad peaks in photoemission