Alloying and Structure of Ultrathin Gallium Films
on the (111) and (110) Surfaces of Palladium
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Abstract
Growth, thermal stability, and structure of ultrathin gallium films
on Pd(111) and Pd(110) are investigated by low-energy ion scattering
and low-energy electron diffraction. Common to both surface orientations
are growth of disordered Ga films at coverages of a few monolayers
(<i>T</i> = 150 K), onset of alloy formation at low temperatures
(<i>T</i> ≈ 200 K), and formation of a metastable,
mostly disordered 1:1 surface alloy at temperatures around 400–500
K. At higher temperatures a Ga surface fraction of ∼0.3 is
slightly stabilized on Pd(111), which we suggest to be related to
the formation of Pd<sub>2</sub>Ga bulk-like films. While on Pd(110)
only a Pd-up/Ga-down buckled surface was observed, an inversion of
buckling was observed on Pd(111) upon heating. Similarities and differences
to the related Zn/Pd system are discussed