Search

A single layer of bismuth deposited on the Cu(100) surface forms long range ordered structural phases at various Bi density. A highly ordered c(2×2) reconstruction is accomplished at 0.5 ML, further Bi deposition induces a c(92×2)R45° structure and a subsequent p(10×10) phase related to the formation of regular dislocations arrays. The transition from a c(2×2) superstructure to the c(92×2)R45° phase is accompanied by a sudden decrease in the work function. Photoemission measurements reveal that the Bi induced states close to the Fermi level, associated to the c(2×2) phase, are strongly quenched when the arrays of dislocations are formed, while at higher binding energies, they undergo an energy shift probably due to a confinement effect. The low-energy single particle excitations and the electron dispersion of the Bi induced states of the c(2×2) phase are compared to the electronic states deduced by theoretical band structure obtained by ab initio calculation performed within the embedding method applied to a realistic semi-infinite system. [ABSTRACT FROM AUTHOR]

In this work we use nonlinear optical properties of Ga nanoparticles monolayers of different average sizes embedded in dielectric matrices to investigate the liquid-solid phase transitions in these materials. Ga nanoparticles, formed by exploiting the partial wetting of liquid Ga over a SiOx surface are irradiated with fs laser pulses from a Ti:sapphire source. The resulting Second Harmonic (SH) generated in the reflection and transmission directions is measured along the phase transitions by cooling the sample from 320 K down to liquid nitrogen temperature. Hysteresis cycles are observed in the nonlinear transmission, which exhibit a strong amplification from the solid to liquid values as compared to the linear optical results. A simple model for SH generation, based on Mie scattering calculations which includes the effect of surface plasmon resonance provides a fair key for the interpretation of the observed effects. [ABSTRACT FROM AUTHOR]