In-situ observation of temperature-dependent segregation of Ni adatoms on oriented Pd surfaces

Abstract

We report the direct observation of the in-situ temperature-dependent surface segregation of Ni adatoms on single crystalline Pd surfaces using Positron annihilation induced Auger Electron Spectroscopy (PAES). For this study, a single atomic layer of Ni was grown on Pd with the crystallographic orientations Pd(111), Pd(110) and Pd(100). The sample temperature was increased from room temperature to 350${}^{\circ }$C and the intensity of the Ni and Pd signal was evaluated from the recorded PAES spectra. Due to the outstanding surface sensitivity of PAES a clear tendency for Pd segregation was observed for all samples. Moreover the activation temperature T${}_0$ for surface segregation was found to depend strongly on the surface orientation: We determined T${}_0$ to 172$\pm$4${}^{\circ }$C, 261$\pm$12${}^{\circ }$C and 326$\pm$11${}^{\circ }$C for Pd(111), Pd(100) and Pd(110), respectively.

arXiv comment6 pages, 3 figures