High temperature electrical resistivity and Seebeck coefficient of Ge2Sb2Te5 thin films

High-temperature characterization of the thermoelectric properties of chalcogenide Ge2Sb2Te5 (GST) is critical for phase change memory devices, which utilize self-heating to quickly switch between amorphous and crystalline states and experience significant thermoelectric effects. In this work, the e...

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Bibliographic Details
Published in:Journal of applied physics 2017-09, Vol.122 (12)
Main Authors: Adnane, L., Dirisaglik, F., Cywar, A., Cil, K., Zhu, Y., Lam, C., Anwar, A. F. M., Gokirmak, A., Silva, H.
Format: Article
Language:English
Subjects:
Applied physics
Computer memory
Crystal structure
Crystallinity
Effective medium theory
Electrical resistivity
Heating
Linearity
Melt temperature
Memory devices
Parameter estimation
Percolation
Phase transitions
Seebeck effect
Silicon dioxide
Temperature
Temperature dependence
Thermal expansion
Thermoelectricity
Thin films
Thomson coefficient
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Summary:High-temperature characterization of the thermoelectric properties of chalcogenide Ge2Sb2Te5 (GST) is critical for phase change memory devices, which utilize self-heating to quickly switch between amorphous and crystalline states and experience significant thermoelectric effects. In this work, the electrical resistivity and Seebeck coefficient are measured simultaneously as a function of temperature, from room temperature to 600 °C, on 50 nm and 200 nm GST thin films deposited on silicon dioxide. Multiple heating and cooling cycles with increasingly maximum temperature allow temperature-dependent characterization of the material at each crystalline state; this is in contrast to continuous measurements which return the combined effects of the temperature dependence and changes in the material. The results show p-type conduction (S > 0), linear S(T), and a positive Thomson coefficient (dS/dT) up to melting temperature. The results also reveal an interesting linearity between dS/dT and the conduction activation energy for mixed amorphous-fcc GST, which can be used to estimate one parameter from the other. A percolation model, together with effective medium theory, is adopted to correlate the conductivity of the material with average grain sizes obtained from XRD measurements. XRD diffraction measurements show plane-dependent thermal expansion for the cubic and hexagonal phases.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4996218