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Title: Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge[subscript 2]Sb[subscript 2]Te[subscript 5] phase-change memory alloy

Abstract

Ge-Sb-Te-based phase-change memory is one of the most promising candidates to succeed the current flash memories. The application of phase-change materials for data storage and memory devices takes advantage of the fast phase transition (on the order of nanoseconds) and the large property contrasts (e.g., several orders of magnitude difference in electrical resistivity) between the amorphous and the crystalline states. Despite the importance of Ge-Sb-Te alloys and the intense research they have received, the possible phases in the temperature-pressure diagram, as well as the corresponding structure-property correlations, remain to be systematically explored. In this study, by subjecting the amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} (a-GST) to hydrostatic-like pressure (P), the thermodynamic variable alternative to temperature, we are able to tune its electrical resistivity by several orders of magnitude, similar to the resistivity contrast corresponding to the usually investigated amorphous-to-crystalline (a-GST to rock-salt GST) transition used in current phase-change memories. In particular, the electrical resistivity drops precipitously in the P = 0 to 8 GPa regime. A prominent structural signature representing the underlying evolution in atomic arrangements and bonding in this pressure regime, as revealed by the ab initio molecular dynamics simulations, is the reduction of low-electron-density regions, which contributes to themore » narrowing of band gap and delocalization of trapped electrons. At P > 8 GPa, we have observed major changes of the average local structures (bond angle and coordination numbers), gradually transforming the a-GST into a high-density, metallic-like state. This high-pressure glass is characterized by local motifs that bear similarities to the body-centered-cubic GST (bcc-GST) it eventually crystallizes into at 28 GPa, and hence represents a bcc-type polyamorph of a-GST.« less

Authors:
; ; ; ; ; ; ;  [1]
  1. Beijing U
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
FOREIGNONRDOE - BASIC ENERGY SCIENCES
OSTI Identifier:
1039459
Resource Type:
Journal Article
Journal Name:
Proceedings of the National Academy of Sciences PNAS
Additional Journal Information:
Journal Volume: 109; Journal Issue: 18; Journal ID: ISSN 1091-6490
Country of Publication:
United States
Language:
ENGLISH
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ALLOYS; BCC LATTICES; BONDING; CHALCOGENIDES; ELECTRIC CONDUCTIVITY; GLASS; MEMORY DEVICES; PRESSURE DEPENDENCE; SALT DEPOSITS; STORAGE; THERMODYNAMICS; TRAPPED ELECTRONS

Citation Formats

Xu, M, Cheng, Y Q, Wang, L, Sheng, H W, Meng, Y, Yang, W G, Hang, X D, Ma, E, JHU), CIW), and George Mason). Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge[subscript 2]Sb[subscript 2]Te[subscript 5] phase-change memory alloy. United States: N. p., 2012. Web. doi:10.1073/pnas.1119754109.
Xu, M, Cheng, Y Q, Wang, L, Sheng, H W, Meng, Y, Yang, W G, Hang, X D, Ma, E, JHU), CIW), & George Mason). Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge[subscript 2]Sb[subscript 2]Te[subscript 5] phase-change memory alloy. United States. doi:10.1073/pnas.1119754109.
Xu, M, Cheng, Y Q, Wang, L, Sheng, H W, Meng, Y, Yang, W G, Hang, X D, Ma, E, JHU), CIW), and George Mason). Tue . "Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge[subscript 2]Sb[subscript 2]Te[subscript 5] phase-change memory alloy". United States. doi:10.1073/pnas.1119754109.
@article{osti_1039459,
title = {Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge[subscript 2]Sb[subscript 2]Te[subscript 5] phase-change memory alloy},
author = {Xu, M and Cheng, Y Q and Wang, L and Sheng, H W and Meng, Y and Yang, W G and Hang, X D and Ma, E and JHU) and CIW) and George Mason)},
abstractNote = {Ge-Sb-Te-based phase-change memory is one of the most promising candidates to succeed the current flash memories. The application of phase-change materials for data storage and memory devices takes advantage of the fast phase transition (on the order of nanoseconds) and the large property contrasts (e.g., several orders of magnitude difference in electrical resistivity) between the amorphous and the crystalline states. Despite the importance of Ge-Sb-Te alloys and the intense research they have received, the possible phases in the temperature-pressure diagram, as well as the corresponding structure-property correlations, remain to be systematically explored. In this study, by subjecting the amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} (a-GST) to hydrostatic-like pressure (P), the thermodynamic variable alternative to temperature, we are able to tune its electrical resistivity by several orders of magnitude, similar to the resistivity contrast corresponding to the usually investigated amorphous-to-crystalline (a-GST to rock-salt GST) transition used in current phase-change memories. In particular, the electrical resistivity drops precipitously in the P = 0 to 8 GPa regime. A prominent structural signature representing the underlying evolution in atomic arrangements and bonding in this pressure regime, as revealed by the ab initio molecular dynamics simulations, is the reduction of low-electron-density regions, which contributes to the narrowing of band gap and delocalization of trapped electrons. At P > 8 GPa, we have observed major changes of the average local structures (bond angle and coordination numbers), gradually transforming the a-GST into a high-density, metallic-like state. This high-pressure glass is characterized by local motifs that bear similarities to the body-centered-cubic GST (bcc-GST) it eventually crystallizes into at 28 GPa, and hence represents a bcc-type polyamorph of a-GST.},
doi = {10.1073/pnas.1119754109},
journal = {Proceedings of the National Academy of Sciences PNAS},
issn = {1091-6490},
number = 18,
volume = 109,
place = {United States},
year = {2012},
month = {5}
}