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Title: Activation energy of metastable amorphous Ge 2Sb 2Te 5 from room temperature to melt

Abstract

Resistivity of metastable amorphous Ge 2Sb 2Te 5 (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/K 2 for an activation energymore » of zero and a Fermi level 0.16 eV below the valance band edge.« less

Authors:
 [1]; ORCiD logo [1];  [2]; ORCiD logo [1];  [1]; ORCiD logo [3];  [1];  [4]; ORCiD logo [1];  [1]
  1. Univ. of Connecticut, Storrs, CT (United States)
  2. Univ. of Connecticut, Storrs, CT (United States); Eskisehire Osmangasi Univ. (Turkey)
  3. Univ. of Connecticut, Storrs, CT (United States); Atilim Univ., Ankara (Turkey)
  4. IBM, Yorktown Heights, NY (United States). Thomas J. Watson Research Center
Publication Date:
Research Org.:
Univ. of Connecticut, Storrs, CT (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1499133
Alternate Identifier(s):
OSTI ID: 1454344
Grant/Contract Number:  
SC0005038
Resource Type:
Accepted Manuscript
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 8; Journal Issue: 6; Journal ID: ISSN 2158-3226
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Muneer, Sadid, Scoggin, Jake, Dirisaglik, Faruk, Adnane, Lhacene, Cywar, Adam, Bakan, Gokhan, Cil, Kadir, Lam, Chung, Silva, Helena, and Gokirmak, Ali. Activation energy of metastable amorphous Ge2Sb2Te5 from room temperature to melt. United States: N. p., 2018. Web. doi:10.1063/1.5035085.
Muneer, Sadid, Scoggin, Jake, Dirisaglik, Faruk, Adnane, Lhacene, Cywar, Adam, Bakan, Gokhan, Cil, Kadir, Lam, Chung, Silva, Helena, & Gokirmak, Ali. Activation energy of metastable amorphous Ge2Sb2Te5 from room temperature to melt. United States. doi:10.1063/1.5035085.
Muneer, Sadid, Scoggin, Jake, Dirisaglik, Faruk, Adnane, Lhacene, Cywar, Adam, Bakan, Gokhan, Cil, Kadir, Lam, Chung, Silva, Helena, and Gokirmak, Ali. Wed . "Activation energy of metastable amorphous Ge2Sb2Te5 from room temperature to melt". United States. doi:10.1063/1.5035085. https://www.osti.gov/servlets/purl/1499133.
@article{osti_1499133,
title = {Activation energy of metastable amorphous Ge2Sb2Te5 from room temperature to melt},
author = {Muneer, Sadid and Scoggin, Jake and Dirisaglik, Faruk and Adnane, Lhacene and Cywar, Adam and Bakan, Gokhan and Cil, Kadir and Lam, Chung and Silva, Helena and Gokirmak, Ali},
abstractNote = {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 Tmelt ~ 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.},
doi = {10.1063/1.5035085},
journal = {AIP Advances},
number = 6,
volume = 8,
place = {United States},
year = {2018},
month = {6}
}

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