本論文主要是探討量子侷限效應外層狀半導體具有不同厚度的二硫化鉬(MoS2)及二硫化鎢(WS2)奈米結構之電傳輸特性。研究結果發現利用簡單的機械剝離法所產生的奈米結構表現出比塊材晶體要高出了幾個數量級的電導率。與此同時，也觀察到二硫化鉬和二硫化鎢奈米結構其載子的活化能相較於同質的塊材還要小，這些結果暗示這兩種層狀半導體可能擁有較高的表面傳導率或較高的表面載子濃度。實驗上也排除了人為因素所影響導致在表層形成較高電子濃度之可能性，包含基板的載子注入與由離子束轟擊層狀材料造成表面損傷的情形。該結果進一步驗證這類層狀材料表面電子累積是屬於材料本質的特性，並有可能適用於多數的過渡金屬硫屬化合物（transition metal dichalcogenide semiconductor）層狀的半導體。此外，藉由532奈米波長雷射激發，兩種材料的塊材與奈米結構皆表現出明顯的光電流反應。光電流隨著入射光光強度增加呈現線性增加。藉由計算光電導增益值發現奈米結構高於塊材近六個數量級。環境變化之光電導量測亦顯示這兩種二維奈米材料皆遵循氧氣敏化光電導機制。

Thickness-dependent electronic transport properties in the molybdenum disulphide (MoS2) and the tungsten disulphide (WS2) two-dimensional (2D) nanostructures beyond quantum confinement scale were observed and investigated. It is found that the nanoflakes produced by simple mechanical exfoliation exhibit several orders of magnitude higher conductivity than their bulk counterparts. The smaller activation energies of carrier were also observed for the MoS2 and WS2 nanoflakes in comparison to the bulk counterparts. These results imply the presence of higher surface conductivity or electron surface accumulation in the layer semiconductor systems. In addition, the potential artificial effects, that could result in a high electron density at the surface, including electron injection from the substrate and surface damage by ion bombardment, were excluded. This result further indicates the proposed surface electron accumulation is an inherent characteristic, which might be generally applicable to the transition metal dichalcogenide (TMD) layer semiconductors. In addition, photoconductive properties in the MoS2 and WS2 nanostructures and bulks by the excitation of the wavelength of 532 nm were also investigated. The photoconductive gains of the nanostructures are six orders of magnitude higher than their bulk counterparts. The environments-dependent photoconductivity indicates these layer nanomaterials follow the oxygen-sensitized photoconduction (PC) mechanism.

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