Properties of ultrathin Pb layers on the Ni3Al(1 1 1) face

The atomic structure and morphology of ultrathin Pb layers deposited on the Ni3Al(1 1 1) face in ultrahigh vacuum at the substrate temperature, ranging from 200 K to 950 K, were investigated with the use of Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and directional elastic peak electron spectroscopy (DEPES). The analysis of AES measurements indicates that two-dimensional growth of the first Pb monolayer ‘wetting layer’ takes place for substrate temperature 200 K ≤ T ≤ 650 K. For T = 200 K, lead on the Ni3Al(1 1 1) grows layer-by-layer, while for T = 300 K flat three atomic-layer-high islands seem to grow after the completion of the first lead monolayer. Above 350 K, the Stranski–Krastanov growth mode is observed. The ordered LEED patterns corresponding to p(4 × 4) and p(√3 × √3)R30° structures are observed. AES and LEED data indicate that lead atoms and the Ni3Al(1 1 1) face form a Pb-Ni3Al(1 1 1) surface alloy. The DEPES results show that the stacking fault abcabcBACBAC or abcabcACBACB is formed in the Ni3Al(1 1 1)–Pb interface region.