Activation energy of metastable amorphous Ge2Sb2Te5 from room temperature to melt

Muneer, Sadid; Scoggin, Jake; Dirisaglik, Faruk; Adnane, Lhacene; Cywar, Adam; Bakan, Gokhan; Cil, Kadir; Lam, Chung; Silva, Helena; Gokirmak, Ali

doi:10.1063/1.5035085

Title: Activation energy of metastable amorphous Ge₂Sb₂Te₅ from room temperature to melt

Journal Article · Wed Jun 13 00:00:00 EDT 2018 · AIP Advances

DOI:https://doi.org/10.1063/1.5035085· OSTI ID:1499133

Muneer, Sadid ^[1];

^[1]; Dirisaglik, Faruk ^[2];

^[1]; Cywar, Adam ^[1];

^[3]; Cil, Kadir ^[1]; Lam, Chung ^[4];

^[1]; Gokirmak, Ali ^[1]

Univ. of Connecticut, Storrs, CT (United States)
Univ. of Connecticut, Storrs, CT (United States); Eskisehire Osmangasi Univ. (Turkey)
Univ. of Connecticut, Storrs, CT (United States); Atilim Univ., Ankara (Turkey)
IBM, Yorktown Heights, NY (United States). Thomas J. Watson Research Center

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 super-cooled 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 ~377 meV at ~465 K and reaching zero at ~930 K, using a reference activation energy of 111 meV (3kBT/2) at melt. Amorphous GST is expected to behave as a p-type semiconductor at T_melt ~ 858 K and transitions from the semiconducting-liquid phase to the metallic-liquid phase at ~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 _μV/K² for an activation energy of zero and a Fermi level 0.16 eV below the valance band edge.

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Research Organization:: Univ. of Connecticut, Storrs, CT (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

Grant/Contract Number:: SC0005038

OSTI ID:: 1499133

Alternate ID(s):: OSTI ID: 1454344

Journal Information:: AIP Advances, Vol. 8, Issue 6; ISSN 2158-3226

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 9 works

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Modeling heterogeneous melting in phase change memory devices Scoggin, J.; Woods, Z.; Silva, H. Applied Physics Letters, Vol. 114, Issue 4 https://doi.org/10.1063/1.5067397	journal	January 2019