The 3ω Method for Analyzing the Thermal Conductivities of Chalcogenide Thin Films and Their AC Impedance Properties
碩士 === 國立交通大學 === 材料科學與工程學系 === 99 === This study investigates the thin-film thermal conduction properties of Ge2Sb2Te5 (GST) phase-change alloys by utilizing a self-assembly apparatus based on the 3-omaga (3ω) method. First, the thermal conduction of silicon dioxide (SiO2) was measured in order to...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2010
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| Online Access: | http://ndltd.ncl.edu.tw/handle/20305979471356202270 |
| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系 === 99 === This study investigates the thin-film thermal conduction properties of Ge2Sb2Te5 (GST) phase-change alloys by utilizing a self-assembly apparatus based on the 3-omaga (3ω) method. First, the thermal conduction of silicon dioxide (SiO2) was measured in order to identify the reliability of experimental tools. The pristine GST and cerium-doped GST (GST-Ce) thin films were then prepared and their thermal conductivities were measured by the 3ω apparatus. The AC impedance properties of these chalcogenide layers were also evaluated by an in-situ electrical measurement system. The data obtained were then implanted in an equivalent circuit model in order to distinguish the characteristics of grain and grain boundary in the electrical and thermal conduction properties of chalcogenide layers. Experimental results indicated that the intrinsic thermal conductivity of amorphous GST (= 0.35 W/mK) was lower than that of crystalline GST (= 0.8 W/mK) and the Ce doping causes the decrease of thermal conductivity in comparison with the GST of the same microstructure. Electrical analysis revealed grain boundary is the major contributor to the resistance property of GST. This was further confirmed by the grain refinement in GST-Ce sample as revealed by x-ray diffraction analysis as well as the increase of phase-change temperature and activation energy of doped GST layer caused by the stress-induced barrier due to the incorporation of alien atoms in the sample. Analysis of characteristic tangent loss peak shift as a function of temperature shows that Ce doping amplifies the interfacial polarization in GST. A calculation of grain-boundary scattering coefficient illustrates the fine grain structure in GST-Ce implies a more severe electron scattering, leading to the decrease of thermal conductivity and increase of electrical resistance property.
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