本論文主要探討以化學汽相傳輸法成長菱形晶系(3R)二硫化鈮與六方晶系(2H)二硒化鈮層狀晶體之二維奈米結構電傳輸特性。利用機械剝離法分離層狀單晶並利用聚焦式離子束技術製作二維奈米結構元件。結果顯示二硫化鈮及二硒化鈮奈米結構之電導率遠小於塊材，低溫暗電導量測也證實奈米結構表現出半導體傳輸特性，此結果不同於塊材之金屬性。此外，塊材與奈米結構在溫度低於200 K時發現不連續的電導率變化，此現象推測為Charge density wave相變。另外，藉由不同波長之光激發，具有半導體性的二硫化鈮及二硒化鈮奈米結構也表現出明顯的光電流反應，光電流隨著光強度增加呈現線性增加。所計算之最佳光電導增益可達100。環境變化之光電導量測顯示這類二維奈米材料遵循氧氣敏化光電導機制。造成二硫化鈮與二硒化鈮的奈米結構與塊材具有不同電傳導特性背後之物理機制也將在本論文探討。

The electronic transport properties in individual of nanoflakes three rhombohedral (3R) niobium disulphide (NbS2) and two hexagonal (2H) niobium diselenide (NbSe2) mechanically exfoliated from the bulk crystal grown by chemical vapor transport were investigated. It is found that the conductivitiy values of the single-crystalline nanoflakes are much lower than those of their bulk counterparts. Temperature-dependent conductivity measurements show that the 3R-NbS2 and 2H-NbSe2 nanoflakes exhibit semiconducting transport behavior, which are also different from the metallic character in the bulk crystals. In addition, the noncontinuous conductivity variations were observed at the temperature below 200K for both nanoflakes and bulks, which is attributed to probable charge density wave (CDW) transition. In addition, the photoconduction properties in semiconducting nanoflakes were also observed the different wavelength excitation. The photocurrent increases with an increase of light intensity. The optical photoconductivity gain of the nanoflakes devices can reach 100. The environment-dependent photoconductivity measurement indicates that these layer nanomaterials follow the oxygen-sensitive photoconduct mechanism. The probable mechanism resulting in different transport behaviors between the NbS2 and NbSe2 nanoflake and bulk were discussed.

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