On the low-temperature growth of Pb on Cu (100)

Abstract

The morphology and structure of Pb deposits on Cu(100) between 150 and 220 K is investigated using low-energy electron diffraction (LEED), auger electron spectroscopy (AES) and scanning tunneling microscopy (STM). It is found that Pb grows along a 〈111〉 axis, with Pb〈110〉 parallel to Cu〈100〉. In the surface plane, this relationship of epitaxy induces tensile stress of 3.1% in the direction of the common axis and compressive stress of −0.8% in the perpendicular direction. Starting from the wetting monolayer made above room temperature, the growth proceeds by a three regime sequence. The growth of a complete bilayer is followed by a quasi layer-by-layer regime which switches, at a temperature-dependent critical coverage, into a three-dimensional pyramidal growth mode. LEED observations suggest that the stresses are fully relaxed by the bilayer. These results are shown to be in good agreement with published thermal energy atom scattering (TEAS) data obtained on the same system. It is shown that the transition from the quasi layer-by-layer regime to the three-dimensional pyramidal growth mode is triggered by the development of islands with a triangular shape, which results in a limitation of the mass transport between atomic Pb layers.