Showing papers by "Peter H. Beton published in 1998"

C 60 -terminated Si surfaces: Charge transfer, bonding, and chemical passivation

Abstract: The interaction of ${\mathrm{C}}_{60}$ with the Si(111)-(7\ifmmode\times\else\texttimes\fi{}7) and Si(100)-(2\ifmmode\times\else\texttimes\fi{}1) surfaces has been investigated using synchrotron radiation core-level and valence-band photoelectron spectroscopy. ${\mathrm{C}}_{60}$ induces distinct spectral changes in the $\mathrm{S}\mathrm{i}\ensuremath{-}2p$ core-level emission from both surfaces, indicative of charge transfer to the adsorbed fullerene molecules. Our results suggest that ${\mathrm{C}}_{60}$ adsorption on Si(111) induces a redistribution of charge within the (7\ifmmode\times\else\texttimes\fi{}7) unit cell involving electron transfer from rest atom to adatom dangling bonds. For a one monolayer coverage [on both Si(111) and Si(100)], broad ${\mathrm{C}}_{60}$-induced chemically shifted components are present in the core-level spectra. Valence-band spectra, however, show no evidence for a high degree of electron occupation of the ${\mathrm{C}}_{60}$ lowest unoccupied molecular orbital. We present core-level data which illustrate that adsorption of a ${\mathrm{C}}_{60}$ monolayer inhibits ambient oxidation of the Si surface.

Optical anisotropy in arrow-shaped InAs quantum dots

Abstract: We have observed a direct correlation between nonspherical shape and polarization anisotropy of optical transitions in quantum dots. The dots, grown by self-assembling during epitaxial deposition of InAs on $\mathrm{GaAs}(311)A,$ exhibit a nonconventional, faceted, arrowheadlike shape aligned in the [2\ifmmode\bar\else\textasciimacron\fi{}33] direction. The dot photoluminescence emission is partially $(\ensuremath{\approx}13%)$ polarized along the same [2\ifmmode\bar\else\textasciimacron\fi{}33] direction. The presence and the sign of the emission polarization is in agreement with the predictions of a theoretical model. Full morphological and optical characterization is reported.

Probing the interactions of on Si(100)- using anisotropic molecular manipulation

Abstract: We have investigated the response of molecules adsorbed on to manipulation induced by a scanning tunnelling microscope. Our results show that the interaction is greater than the interaction. Attempts to move a molecular pair result in the transfer of one molecule across a dimer row due to barrier lowering caused by the intermolecular interaction. Our results suggest that is chemisorbed and this is confirmed by Si 2p core-level photoemission spectra.