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

Applied Surface Science, Volume 273,  2013, Pages 554-561.

K. Miśków, A. Krupski.

Institute of Experimental Physics, University of Wrocław, pl. Maxa Borna 9, PL 50-204 Wrocław, Poland and

Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom

 

Abstract

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.

 

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Additional Information

The morphology, atomic and electronic structure of ultrathin Pb layers deposited on the Ni3Al(111) super alloy 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-energyelectron diffraction (LEED), directional elastic peak electron spectroscopy (DEPES), and scanning tunnelling microscopy (STM) [1-3]. The analysis of AES and STM measurements indicate 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(111) 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)R30o structures are observed. AES and LEED data indicate that lead atoms and the Ni3Al(111) face form a Pb-Ni3Al(111) surface alloy [1]. The DEPES and multiple scattering approximationresults show that the stacking fault abcabcABCABC or abcabcBACBAC is formed in the Ni3Al(111)-Pb interface region.Above q> 1.0 ML, a three-dimensional growth of the Pb islands was observed with a strongly preferred atomic scale ‘magic height (N),’ hexagonal shape and flat-tops. At coverage q= 3.5 ML, only islands containing N = 3, 5, 7 and 11 atomic layers of Pb are observed. At the higher coverage q= 5.5 ML, three types of regular hexagonal islands with side lengths of 25, 30 and 45 nm are observed. Furthermore, three different island adsorption configurations with respect to each other were observed. After an annealing at T = 400 K of 5.5 ML of lead deposited at RT on the Ni3Al(111) the morphology of the surface changes. Post-anneal, islands of Pb are observed above the ‘wetting layer’ with an estimated average size and diameter of 768 nm 2± 291 nm 2 and 38.17 ± 6.56 nm and constant uniform height of two atomic layers (N = 2).Density functional theory calculations (DFT) with the use of CASTEP code for descibingatomic and electronic structure of the Pb/Ni3Al(111) system are in progress [4].

 

[1] K. Miśków, A. Krupski, Appl. Surf. Sci. 273 (2013) 554.

[2] K.Miśków, A. Krupski, K. Wandelt, Vacuum 101 (2014) 71.

[3] A. Krupski, Journal of Physics: Condensed Matter 26 (2014) 053001.

[4] K. Krupski, A. Krupski (2014) before submission.

 

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

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