We present an angle-resolved photoemission study of a ternary phase change material, namely Ge2Sb2Te5, epitaxially grown on Si(111) in the metastable cubic phase. The observed upper bulk valence band shows a minimum at Γ¯ being 0.3 eV below the Fermi level EF and a circular Fermi contour around Γ¯ with a dispersing diameter of 0.27–0.36 Å−1. This is in agreement with density functional theory calculations of the Petrov stacking sequence in the cubic phase which exhibits a topological surface state. The topologically trivial cubic Kooi-De Hosson stacking shows a valence band maximum at Γ in line with all previous calculations of the hexagonal stable phase exhibiting the valence band maximum at Γ for a trivial Z2 topological invariant ν0 and away from Γ for non-trivial ν0. Scanning tunneling spectroscopy exhibits a band gap of 0.4 eV around EF.
9 Dec 2013
Volume: 103 Issue: 24 Pages: 243109
Applied Physics Letters