RESUMEN
The interaction of Ca evaporated in vacuum onto a 2H-NbSe2 surface held at room temperature was studied by photoelectron spectroscopy. Indications of an intercalation reaction were observed initially, but larger Ca depositions resulted in a layer-breaking reaction producing a disordered overlayer of varying compositions. The layer-breaking reaction is likely due to the intercalation compound becoming unstable as the local Ca concentration exceeds the threshold value. Continued Ca depositions eventually resulted in the growth of three-dimensional islands of Ca metal, exposing relatively unaffected NbSe2 layers between the Ca islands.
RESUMEN
Photoemission microspectroscopy on the layered misfit compound (PbS)1.13TaS2 provides direct evidence for Ta substitution into PbS layers as well as for Pb substitution into TaS2 layers. This metal cross substitution alters the charge balance between alternating layers and can explain the remarkable stability of (PbS)1.13TaS2 and, possibly, of analogous misfit compounds. It is suggested that even formally stoichiometric misfit compounds can be stabilized by this mechanism.