Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 19: Semiconductor Substrates: Structure, Adsorption and Growth

O 19.1: Poster

Montag, 7. März 2016, 17:00–19:30, Poster A

Epitaxial Growth of Ultrathin Lead Films on Silicon (111) — •Tobias Witte, Tim Frigge, Bernd Hafke, Boris Krenzer, and Michael Horn-von Hoegen — Department of Physics, University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany

Epitaxial growth of ultrathin Pb films on Si(111) was studied by means of high resolution electron diffraction (SPA-LEED). The β(√3×√3) reconstruction with 1/3 ML Pb-coverage (1 ML = 1 Pb atom per Si surface atom = 7.84× 10¹⁴ Pb atoms/cm²) was prepared by desorption of a larger amount of Pb at 450 ^∘C and used as a template layer for deposition. The layer-by-layer growth mode of Pb for coverages larger than 3 ML was confirmed through LEED intensity oscillations during deposition at low temperatures of 100 K. In the coverage regime of 1-3 ML the diffracted intensity is strongly reduced, indicating roughening of the strained Pb film. Films with 3-5 ML thickness are laterally relaxed through a network of interfacial misfit dislocations which is observed through satellite spots surrounding all integer order spots in the diffraction pattern. A G(S)-analysis indicates an increased vertical layer distance of 3.05 Å, which relaxes towards the bulk-like value of 2.87 Å for films of 6 or more ML thickness. This behavior is corroborated through the LEED intensity oscillations during deposition, which were measured at different diffraction conditions (i.e. different electron energies). Films deposited on the β(√3×√3) reconstruction exhibit a slight azimuthal disorder, which is reflected through banana-like distorted integer order spots in the diffraction pattern. These films are metastable and form islands at temperatures above 220 K.