本論文將研究高導電度硫屬化合物之傳輸特性，首先，我們使用化學氣相傳導法(Chemical Vapor Transport，CVT）並以碘作為傳導劑成長二硫化鈦(TiS2)與二硒化鈦(TiSe2) 之層狀化合物，並對此晶體進行晶體結構分析，及光學、光化學、電學及熱電量測之研究及討論，並且一同探討實驗室成長出高導電度晶體 ─ 硫化錫(SnS)與硒化錫(SnSe)之熱電特性。
我們利用X-Ray晶格繞射分析儀 (X-Ray Diffraction，XRD) 分析TiS2與TiSe2系列之結構皆為六方1T堆疊相，晶格常數TiS2為a=3.393 Å，c=5.719 Å，而TiSe2的為a=3.502 Å，c=5.997 Å，以雷射為激發源量測拉曼散射光譜 (Raman Scattering Spectra) 可得到拉曼模態Eg與A1g。透過X光繞射與拉曼散射光譜可確認SnS與SnSe兩者均為正交晶系，且會因光的偏振方向差異而使某些震動訊號呈現選擇定律，因此晶軸具有極化特性，藉由電子能量損失譜 (Electron Energy Loss Spectroscopy，EELS) 量測實驗及光穿透光譜(Photo Transmission，Tr) ，分別對樣品進行實驗，可觀測TiS2與TiSe2能隙位置分別在1eV與0.8eV，在電漿共振光譜中與霍爾量測結果可發現，其濃度高達〖10〗^20-〖10〗^21 〖cm〗^(-3)，且兩者皆為高導電度層狀化合物。在I-V曲線中與光催化降解實驗可得知，TiS2與TiSe2皆不會因照光而產生光降解效果，並可證明兩者呈現金屬性電子海傳輸之特性。由四點電阻率量測中，可以發現TiS2隨溫度變化之電阻率，呈現金屬特性；而TiSe2隨溫度變化之電阻率，其200K之相轉溫度為二階結構相變，即為材料特性-電荷密度波。此特性可望用來製作效率高且多樣化的電子元件；在熱電實驗中，判斷TiS2與TiSe2皆為N型半導體，而SnS與SnSe均為P型半導體，其中，SnSe在室溫300K時，熱電優值約為0.15，且具有高的導電性與低的熱傳導係數，SnSe極具有潛力發展於熱電元件上。
綜合以上實驗結果，提出高導電度硫屬化合物之傳輸特性，TiS2與TiSe2證實兩者都有一個窄能隙且具有高導電度及高濃度，可望用來研究新型之電子元件；SnS與SnSe皆具有極化特性，可做光學異向特性之應用，其中，SnSe有好的熱電響應，得以提供為未來熱電材料之應用。

In this thesis, we study transfer characteristic of highly conductive-layered chalcogenide crystals. We have synthesized and grown layered semiconductors of TiS2 and TiSe2 by chemical vapor transport (CVT) method using iodine as transport agent. Detailed characterization of the materials was carried out by using X-ray diffraction (XRD), Raman scattering, Transmittance, Electron Energy Loss Spectroscopy (EELS), modulation reflectance, Hall effect measurement, V-I measurement, photodegradation, four-point resistivity measurement and thermoelectric techniques. Meanwhile, we will also demonstrate the thermoelectric properties of highly conductive-layered chalcogenide crystals ─ SnS and SnSe.
According to the results of X-ray diffraction, the TiS2 and TiSe2 belong to one-layer trigonal (1T) stack phase. Lattice constants of TiS2 are a = 3.393 Å, c = 5.719 Å and those of TiSe2 are a = 3.502 Å, c = 5.997 Å. The vibration mode Eg and A1g of these crystals were clearly detected by Raman spectroscopy. From the results of X-ray diffraction, the SnX (X=S, Se) material’s crystal structure is orthorhombic. The vibration modes of SnX (X=S, Se) show selection rule of the linearly polarized light along a and along b axis by Raman spectroscopy. The SnX (X=S, Se) show in-plane anisotropy on the c plane. From the Electron Energy Loss Spectroscopy (EELS) and transmittance results of the TiS2 and TiSe2 show the energy gap are around 1 eV and 0.8 eV at room temperature. In the plasma frequency and Hall effect experiments of TiS2 and TiSe2, they have high concentration to 〖10〗^20-〖10〗^21 〖 cm〗^(-3) and they have high electrical conductivity. Owing to the results of Photo V-I and photocatalysis experiments, we can conclude that the materials don’t have any features of photo-response and then photocatalytic behavior. They are metallic materials with electron sea. The metallic behavior of TiS2 crystal was also confirmed by four-point resistivity measurement, where the resistivity increases with temperature increased from 20 to 300K. The four-point resistivity results of TiSe2 show the second order CDW phase transition near ~200K and which possesses the potential for application in the future electronic devices. For thermoelectric measurements, TiS2 and TiSe2 are N-type semiconductors from their negative thermoelectric voltage sign. On the other hand, the SnS and SnSe are P-type semiconductors with positive thermoelectric voltage. The highest figure of merit with ZT~ 0.15 has been achieved in SnSe around 300K and which has high conductivity and low thermal conductivity so that SnSe has the potential applying in thermoelectric devices.
From all the experimental observations, we can infer that the TiS2 and TiSe2 have a narrow energy gap, high conductivity, and high carrier concentration. It provides scientific information for future technological applications. SnX (X=S, Se) have the orientation character and they could be applied to optical device applications. Furthermore, SnSe has better thermoelectric response. It is a suitable candidate for application in thermoelectric devices.

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