本論文研究高導電性過渡性金屬鈮和鉭雙硫屬化合物的晶體成長與載子傳輸性質研究，利用化學氣相傳導法並以碘作為傳導劑成長二硒化鈮 (NbSe2) 、二硫化鈮 (NbS2) 及二硫化鉭 (TaS2) 之高導電性層狀化合物，並對此系列晶體進行晶體結構分析、電性及熱電特性量測之研究及討論。藉由能量色散X射線譜確認成長材料之元素比例與預期成分相符，透過X-Ray晶格繞射及拉曼量測分析NbSe2及TaS2之結構為六方2H堆疊相，而NbS2為六方3R堆疊相。在照光V-I曲線中，NbSe2、NbS2及TaS2在照光前後皆不受光觸發影響；霍爾量測結果皆呈現N型特性，四種材料載子濃度都高達1021 cm-3，皆為高導電度層狀化合物；藉由變溫電阻率的量測中，可以發現三者材料隨溫度變化的電阻率都是呈現出金屬性的溫變行為。熱電量測實驗中，判斷三者材料皆為N型，其中NbSe2有較大的Seebeck係數與較低的電阻率，功率因子在三種材料為最高，在室溫下可得其熱電優值約為0.37，適合發展在熱電元件的應用上。

This work reports crystal growth and carrier transport properties of high-conductivity transition metals (i.e. niobium and tantalum) dichalcogenides. Niobium diselenide (NbSe2), niobium disulfide (NbS2) and tantalum disulfide (TaS2) are highly conductive layered compounds. We will conduct research and discussion on the analysis of crystal structure, electrical, and thermoelectric characteristics of the series crystals. The single crystals of NbSe2, NbS2 and TaS2 were grown using chemical vapor transport (CVT) method with iodine as the transport agent. The energy dispersive X-ray spectrum confirms that the element ratio of the grown material is consistent with the expected composition. NbSe2 and TaS2 is a hexagonal 2H stacking phase, while NbS2 is a hexagonal 3R phase through X-Ray diffraction and Raman measurement. In the illumination VI curves, NbSe2, NbS2, and TaS2 are not affected by the light before and after the illumination. Hall measurement results show that all samples are N-type materials, and the carrier concentration of the three materials ranges from 1021 cm-3 to 1022 cm-3. All the samples are highly conductive layered compound. Based on the temperature-dependent resistivity, it can be found that the resistivity of the three materials changes to very low as the temperature decreases. So it can be concluded that all samples show the metallic behavior. The thermoelectric measurement also confirms that the three materials are all N-type, the same as the Hall measurement result. Among them, NbSe2 has a higher Seebeck coefficient and a lower resistivity. NbSe2 has the highest power factor and figure of merit (ZT ~0.37) compared to the other materials. It has the potential to be developed in thermoelectric and energy application.

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