Structural and chemical investigation of epitaxial interfaces and of metastable surface alloys

Abstract The formation of the Pt/Co(10 1 0) interface has been investigated by AES, XPS, UPS and LEED. We evidence, at room temperature, a quasi-layer-by-layer growth mode with the presence of a slight interdiffusion process at the interface. Through a rather simple kinematical approach of the LEED patterns, we discuss both the in-plane and out-of-plane parameters of the layers. At room temperature, when increasing thicknesses, the long-range order is progressively lost and the epilayer undergoes a structural transition (1×1)→C(2×2)→(1×1). The formation of metastable alloys stabilized in the near surface region has been investigated by AES, XPS, UPS, EELS and LEED for both growth at 600 K and anneals. The growth at 600 K leads to a perfect rotational epitaxy and ends up with a Pt 2 Co alloy layer on top of which pure Pt layers grow. Annealing of room temperature deposited layers improves the structural quality of the layer and in some cases leads to reconstructions enhancing the layer density. In this case interdiffusion needs a 2.5 ML (monolayer) critical thickness. The composition of the alloyed layer is driven by the temperature and not by the annealing time, evidencing the metastable nature of the surface alloys.