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Metal-insulator transition and doping-induced phase change in Ge 2 Sb 2 Se 5 x Te 5 - 5 x

Title
Metal-insulator transition and doping-induced phase change in Ge 2 Sb 2 Se 5 x Te 5 - 5 x
Authors
Xu, ZhenyangPark, KeeseongSchneeloch, John A.Louca, Despina
DGIST Authors
Park, Keeseong
Issue Date
2020-11
Citation
Applied Physics Letters, 117(19), 193503
Type
Article
Article Type
Article
Author Keywords
Hexagonal phaseInduced phase changeLiquid nitrogen quenchedMetal-to-insulator transitionsOptical characteristicsOrders of magnitudeMetal insulator transitionActivation energyAntimonyAntimony compoundsDoping (additives)GermaniumGermanium compoundsGround stateLiquefied gasesMetal insulator boundariesNanocrystalline materialsPhase change materialsSalt depositsSeleniumSemiconductor insulator boundariesTelluriumAmorphous and crystalline phasisHexagonal crystals
Keywords
KINETICSCRYSTALLIZATIONDIFFRACTIONFILMS
ISSN
0003-6951
Abstract
Ge2Sb2Te5 (GST-225), a phase change material (PCM) with vast differences in the electrical and optical characteristics between its amorphous and crystalline phases, is revisited to explore its properties with Se doping. GST crystallizes in a layered hexagonal ground state, while the precursor to the amorphous state is a distorted rock salt like structure with vacancies at the Ge/Sb sites. Upon doping, liquid nitrogen quenched Ge 2 Sb 2 Se 5 x Te 5 - 5 x (GSST-225) exhibits a direct hexagonal-to-amorphous phase change above x > 0.8, whereas the rock salt like structure appears as a second phase with a volume fraction that does not change as a function of the doping. The phase change is accompanied by a metal-to-insulator transition (MIT), with a several orders of magnitude increase in the resistivity on approaching the amorphous state. A similar MIT is observed even without the phase change in hexagonal crystals with doping levels above x > 0.8. On warming amorphous GSST (x = 0.9) above room temperature, a reversal to the hexagonal phase occurs with a re-crystallization onset temperature (Tc) above 300 °C, much higher than the Tc (∼ 170 °C) of amorphous GST and an activation energy of 1.47 eV, which is comparable to good glass formers. © 2020 Author(s).
URI
http://hdl.handle.net/20.500.11750/12790
DOI
10.1063/5.0030956
Publisher
American Institute of Physics Inc.
Related Researcher
  • Author Park, Keeseong Novel Quantum Materials Laboratory
  • Research Interests Superconductor and magnetic material research; Single and poly crystal compound synthesis; Measurement of material properties in low temperature; Average and Local Atomic structure Analysis with x-ray and neutron scattering
Files:
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Collection:
Department of Emerging Materials ScienceNovel Quantum Materials Laboratory1. Journal Articles


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