本論文利用化學氣相傳導法（Chemical Vapor Transport, CVT）成長過渡金屬二硫屬化物（Transition Metal Dichalcogenides, TMDCs）之二硒化鉿（Hafnium Diselenide, HfSe2）與二硫化鉿（Hafnium Disulfide, HfS2）晶體，並研究材料結構和光電特性。藉由 EDS、XPS、TEM 及 XRD 等儀器量測，確認成長之材料與預期相符，並得知 HfSe2 及 HfS2 皆為六方晶系。由拉曼光譜（Raman）觀察到 HfSe2 具有 Eg、A1g 及 "E" _"2g" ^"1" 三種振動模態，而 HfS2 具有 Eg、A1g 兩種振動模態，並進一步透過極化拉曼及溫度相依實驗觀察不同角度和溫度下，各振動模態的消長變化。光學量測中，利用穿透光譜（Transmittance）與熱調制反射光譜（Thermoreflectance）實驗量測到室溫（300 K）時 HfSe2 具有 1.244 eV能隙，HfS2 具有 2.019 eV能隙，皆為間接能隙，搭配溫度相依實驗可發現能量會隨溫度降低而增加，HfSe2 藍移至 1.315 eV，HfS2 則藍移至 2.065 eV。從電學量測中，透過兩點 V-I 曲線實驗結果得知 HfSe2 兩點電阻率為 8.695×10-2 Ω∙cm、HfS2 兩點電阻率為 5.622×10-1 Ω∙cm。利用熱探針（Hot Probe）及霍爾效應（Hall Effect）量測可知材料皆為 n 型半導體，且 HfSe2 載子濃度為 8.33×1018 cm-3，而 HfS2 載子濃度為 1.08×1018 cm-3。在變溫電阻率實驗中，HfSe2 呈現退化型半導體（Degenerate Semiconductor）行為，HfS2 則是低溫為半導體（Semiconductor）行為，高溫時為退化型半導體行為。最後進行兩材料之熱電量測，結果顯示皆具有高導電度及高 Seebeck 係數。
在拉曼實驗中發現易產生 HfOx 之峰值，因此將材料做變因控制氧化處理，由 EDS 實驗可得知 HfSe2 以及 HfS2 經加溫後逐漸變為 HfOx，在 XPS 實驗中可發現當 HfSe2 氧化後，價帶最高位置變為 0.0548 eV，HfS2 位置變為 0.579 eV。透過霍爾實驗量測，氧化後 HfSe2 濃度變為 1.62×1019 cm-3，電阻率下降變為 2.496×10-2 Ω∙cm，而 HfS2 濃度變為 5.00×1018 cm-3，電阻率亦下降變為 8.169×10-2 Ω∙cm。由上述實驗可以知道 HfSe2 相對於 HfS2 更容易形成 HfOx 化合物，故推測在相同氧化環境中，可發現 HfS2 氧化速率較慢，且導電率較新鮮面之材料更好。概括上述結果顯示兩材料皆具有低電阻率且高導電的特性，有利於開發相關熱電材料。

Chemical Vapor Transport (CVT) method was carried out to grow crystals of transition metal dichalcogenides (TMDCs), specifically Hafnium Diselenide (HfSe2) and Hafnium Disulfide (HfS2). The structure and optoelectronic properties were analyzed through Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD) measurement. HfSe2 and HfS2 had successfully grown, and determined that both HfSe2 and HfS2 possessed a hexagonal crystal structure. Raman spectroscopy revealed that HfSe2 exhibited three vibrational modes: Eg, A1g, and "E" _"2g" ^"1" , while HfS2 exhibited two vibrational modes: Eg and A1g. Further investigation through polarized Raman and temperature-dependent experiments provided insights into the variations of these vibrational modes under different angles and temperatures.
Transmittance and Thermoreflectance experiments determined the bandgap of HfSe2 and HfS2. HfSe2 exhibited an indirect bandgap of 1.244 eV, while HfS2 exhibited an indirect bandgap of 2.019 eV. Temperature-dependent measurements revealed an increase in energy as the temperature decreased to 20 K. HfSe2 was shifted to 1.315 eV, and HfS2 was shifted to 2.065 eV at 20 K. Both samples exhibit a blue-shift behavior and intensity ascent as temperature increased, satisfy the general behavior of semiconductor.
The electrical characterization was done through a two-point V-I curve, Hall-effect, hot probe, resistivity temperature dependent, and thermoelectric measurements. Two-point V-I curve experiments yielded a two-point resistivity of 8.695×10-2 Ω∙cm for HfSe2 and 5.622×10-1 Ω∙cm for HfS2. Hall effect and hot probe measurements indicated that both materials were n-type semiconductors. The carrier concentration for HfSe2 was determined to be 8.33×1018cm-3, while for HfS2, it was 1.08×1018cm-3. In the temperature-dependent resistivity experiments, HfSe2 exhibited degenerate semiconductor behavior, while HfS2 exhibited semiconductor behavior at low temperatures and degenerate semiconductor behavior at high temperatures. Furthermore, thermoelectric measurements of both materials showed high conductivity and Seebeck coefficients.
HfSe2 and HfS2 exhibited an oxidation behavior (HfOx) and were observed through some experiments. Raman measurement revealed that HfOx peaks were quickly generated. Therefore, controlled oxidation treatments were performed on the materials. The EDS experiments confirmed that HfSe2 and HfS2 gradually became HfOx upon heating. The XPS experiments demonstrated that the valence band maximum shifted to 0.0548 eV for oxidized HfSe2 and 0.579 eV for oxidized HfS2. The Hall effect measurements showed that the carrier concentration increased to 1.62×1019 cm-3 for oxidized HfSe2 and 5.00×1018 cm-3 for oxidized HfS2. Based on the above experiments, it was determined that HfSe2 was more prone to forming HfOx compounds than HfS2. Therefore, it can be inferred that HfS2 exhibits a slower oxidation rate than HfSe2 under the same oxidizing environment. Furthermore, the results indicate that the oxidized HfSe2 and HfS2 possess a high conductivity, making them promising for developing related thermoelectric materials.

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