Deposition of Ca on the 2H–NbSe2 surface: Competing processes

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.