Alternative representation of QW Phase accumulation model

Dispersion of k(E)

Synchrotron radiation photoemission spectroscopy ISA Aarhus University Maximum Energy 580 MeV Max Current 250 mA Lifetime 15 hours SGM eV eV

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

Scanning film thickness by moving wedge through laser or synchrotron beam Wedge-shaped metal film 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 Width of synchrotron beam AFM

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

Cu buffer layer Cu 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

Effect of Cu buffer layer

QW levels and film roughness Thickness (ML) Binding Energy (eV) Film thickness variations expected within probed area Variations within a few atomic layer give broad peaks in photoemission Beam size on sample ~1 mm