Regensburg 2013 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 16: Theory: Metal-insulator transitions / Electronic structure calculations
HL 16.6: Vortrag
Montag, 11. März 2013, 17:00–17:15, H13
Metal-Insulator Transitions of Crystalline Phase-Change Materials — •Wei Zhang1, Alexander Thiess2, Peter Zalden1, Rudolf Zeller2, Peter Dederichs2, Jean-yves Raty3, Matthias Wuttig1,4, Stefan Bluegel2,4, and Riccardo Mazzarello1,4 — 1RWTH Aachen, Germany — 2Forschungszentrum Jülich, Germany — 3University of Liege, Belgium — 4JARA, Germany
The study of metal-insulator transitions (MITs) in crystalline solids is a subject of paramount importance. Recently, a metal-insulator transition solely due to disorder has been observed experimentally in the crystalline phase-change material (PCMs) Ge1Sb2Te4 (GST): upon annealing at temperatures T below 548K, the system shows insulating behavior due to Anderson localization; when annealing at higher T, it exhibits metallic properties. In this work, we present an ab initio Density Functional Theory study of this effect. By considering a set of very large models of GST containing one to several thousand atoms and different degree of disorder, we identify the microscopic mechanism which localizes the electron wavefunctions near the Fermi energy in the insulating phase as due to vacancy clustering. The ordering of these vacancy clusters upon annealing eventually drives the system to the metallic phase. Our results about crystalline PCMs could help to extend the capacity of current data storage devices based on PCMs, which only utilize the electrical contrast between the crystalline and the amorphous phase.