Activation energy of metastable amorphous Ge2Sb2Te5 from room temperature to melt

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Muneer S., Scoggin J., Dirisaglik F., Adnane L., Cywar A., Bakan G., ...More

AIP ADVANCES, vol.8, no.6, 2018 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 8 Issue: 6
  • Publication Date: 2018
  • Doi Number: 10.1063/1.5035085
  • Journal Name: AIP ADVANCES
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Eskisehir Osmangazi University Affiliated: Yes


Resistivity of metastable amorphous Ge2Sb2Te5 (GST) measured at device level show an exponential decline with temperature matching with the steady-state thin-film resistivity measured at 858 K (melting temperature). This suggests that the free carrier activation mechanisms form a continuum in a large temperature scale (300 K - 858 K) and the metastable amorphous phase can be treated as a supercooled liquid. The effective activation energy calculated using the resistivity versus temperature data follow a parabolic behavior, with a room temperature value of 333 meV, peaking to similar to 377 meV at similar to 465 K and reaching zero at similar to 930 K, using a reference activation energy of 111 meV (3k(B)T/2) at melt. Amorphous GST is expected to behave as a p-type semiconductor at T-melt similar to 858 K and transitions from the semiconducting-liquid phase to the metallic-liquid phase at similar to 930 K at equilibrium. The simultaneous Seebeck (S) and resistivity versus temperature measurements of amorphous-fcc mixed-phase GST thin-films show linear S-T trends that meet S = 0 at 0 K, consistent with degenerate semiconductors, and the dS/dT and room temperature activation energy show a linear correlation. The single-crystal fcc is calculated to have dS/dT = 0.153 mu V/K-2 for an activation energy of zero and a Fermi level 0.16 eV below the valance band edge. (C) 2018 Author(s).