Ultra thin films of gadolinium deposited by evaporation in ultra high vacuum conditions: Composition, growth and morphology

Ultra-thin gadolinium films with thicknesses between 8 and 101 Å were deposited on AT-cut crystalline quartz substrates under ultra high vacuum conditions, and subsequently subjected to composition and morphologic characterization through X-ray photo-spectroscopy analysis and atomic force microscopy. Oxygen contamination is found on the samples, and its amount is estimated in terms of the thickness of an oxygen layer over the gadolinium films after subtracting the contribution to the XPS spectra of the underlying background. Atomic force microscope pictures provide evidence of having metal island films, with two growing regimes: the Volmer-Weber mode for the thinner films considered and the Stranski-Krastanov growing mode for the thicker ones. From evaluation of the sticking coefficient, the shape of the islands is approximated in terms of oblate spheroid caps and variation of the contact angle with film mass thickness is reported.

Research highlights▶ Conditions to accomplish deposition of ultra thin metal films of Gd were reached. ▶ Ultra thin films with low contamination levels were obtained. ▶ Chemical characterization of the films was carried out. ▶ Morphology of the metal island films was characterized from AFM analysis. ▶ AFM data and presence of oblate spheroid caps of Gd is established are correlated. ▶ Sticking coefficient of Gd/quartz and Gd/Gd, and contact angles, are reported.