Regensburg 2022 – scientific programme
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O: Fachverband Oberflächenphysik
O 30: Semiconductor Surfaces
O 30.2: Talk
Tuesday, September 6, 2022, 11:00–11:15, S053
Dimer coupling energies of the Si(001) surface examined by SPA-LEED — •Christian Brand, Giriraj Jnawali, Jonas Fortmann, Mohammad Tajik, Alfred Hucht, Peter Kratzer, Hamid Mehdipour, Björn Sothmann, and Michael Horn-von Hoegen — Department of Physics and Center for Nanointegration CENIDE, University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg
Though the surface of Si(001) belongs to the most famous in the world still some of its properties and phenomena are unrevealed. Si(001) exhibits buckled dimers in the topmost layer, arranged in dimer rows, and thus forming a (2 × 1) reconstruction at room temperature. Upon cooling the structure undergoes an disorder-order transition to the c(4 × 2) reconstructed ground state. High-resolution SPA-LEED (Spot Profile Analyzing - Low Energy Electron Diffraction) was used to quantify the structural change along the transition upon heating from low to high temperatures. Rapid cooling in the regime of critical slowing down formed a so-called domain structure with typical size of ∼ 14 nm. The data is analyzed in the framework of the anisotropic 2D Ising model and complemented by density functional theory calculations. We determined a phase transition temperature of Tc = 190.6 K, critical exponents β, γ, and ν of the Ising model and the coupling constants J∥= (−24.9 ± 1.3) meV and J⊥= (−0.8 ± 0.1) meV of the Si dimers by solving Onsager’s equation and evaluating the correlation length ratio of the two directions.