First-principles calculation of transport and thermoelectric coefficients in liquid $Ge_{2}Sb_{2}Te_{5}$.

Baratella D., Dragoni D., Bernasconi M.
  Giovedì 15/09   09:00 - 13:00   Aula D - Marianna Ciccone   II - Fisica della materia   Presentazione
Phase change materials are exploited in key enabling technologies such as non-volatile electronic memories. In phase change memories (PCM) the two digital states are encoded in the amorphous and crystalline phases of the $Ge_{2}Sb_{2}Te_{5}$ (GST) alloy that features a difference in the electrical resistivity by about three orders of magnitude. The readout of the memory consists of measuring the resistance at low bias while the set/reset processes consist of the reversible transformation between the two phases induced by Joule heating. Thermoelectric effects play an important role in the programming operations due to the presence of large electric fields and thermal gradients. Numerical simulations based on finite-elements methods have been performed to reproduce the electrical characteristics of PCMs based on GST in the set/reset regimes. The electrothermal modeling of the device requires the knowledge of transport coefficients such as the Seebeck coefficient, the electrical and thermal conductivities at different temperatures. In this contribution, we calculate these transport coefficients of liquid GST at a few temperatures above melting by means of density functional molecular dynamics.