| Summary: | 博士 === 淡江大學 === 物理學系博士班 === 101 === In this thesis, the Mo2S3 doped with Si, C, B, and Ru, is identified to bear the same crystalline structure P21/m as that of Mo2S3 through XRD analysis. Diamagnetic transitions with χm ~ 10-4 emu/g-Oe at temperature ranging from 2K to 6K were observed in the doped samples of SixMo2S3-x (x = 0.1, 0.2, 0.33, 0.5). And both of the x = 0.2 and 0.5 samples were found to have double diamagnetic transitions with higher Tc at the same temperature of 6.01K. While SixMo2S3-x of x = 0.33 displayed an extra ferromagnetic-like response at 63K. The corresponding transition in resistivity of SixMo2S3-x with x = 0.1 was noticed to show a mild drop with less than 10% of its original transition values as measured down to 2K. But a superconducting-like magnetic field dependence on the phase transition of resistivity was also noted. Its diamagnetic signals were greatly reduced when the applied magnetic fields were raised to 103 Oes. In the doped samples of A0.1Mo2S2.9 (A = C, B, and Ru) the phase transition in resistivity at 4.08K, 4.62K, and 4.35K, respectively, exhibited similar fashion as that in the case of Si0.1Mo2S2.9.
For the other bulk samples SiMoS1+x (0≦x≦1), the polycrystalline structure reveals a poorly-crystalline MoS2 phase with several unknown reflections. In SiMoS1.4 all of the unknown reflections could be identified belong to alloy MoSi2 structure, but it is the only sample which doesn’t show diamagnetic transitions. While in the XRD of the rest samples most of the unknown reflections may be assigned to alloy Mo3Si3 structure. The electrical transitions in resistivity of bulk sample SiMoS1+x with x = 0, 0.2, 0.8, and 1, are observed at 4.25K, 4.41K, 3.32K, and 3.75K, respectively. And the samples with x = 0 and 1, reveal diamagnetic transitions at 4.54K and 3.51K, respectively.
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