Suppression of Peierls distortion in thallium chains on silver (100)

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Abstract
LEED, Auger electron spectroscopy, secondary-electron-emission crystal current measurements and angle-resolved photoelectron spectroscopy have been used to study the adsorption of thallium on silver (100). At room temperature and at coverages greater than 0.6 monolayers, LEED indicates the formation of two ordered overlayer structures, each with a (1320) unit mesh; the second of these is ascribed to a dense hexagonal monolayer. At coverages below 0.6 monolayers cooling the sample to 70K produced a bright (1002) pattern or another (1320) pattern, depending on the coverage. Both patterns are ascribed to pseudo-one-dimensional systems. Measurements of binding energy shifts and widths of the thallium 5d core levels are consistent with the authors proposed overlayer structures. The thallium chains in the (1002) overlayer show no evidence for the formation of a Peierls superstructure contrary to the findings for thallium chains on copper (100). Band mapping of the thallium 6p band shows no evidence for a gap at the Fermi level, confirming the LEED result that the Peierls distortion had been suppressed. The authors believe this is due to the commensurability with the substrate.