本論文探討奈米多層結構的二硫化鉬(MoS2)層狀半導體之表面電子聚集效應及其電傳輸特性。本實驗利用機械剝離法產生MoS2奈米結構，發現其電導率與塊材相比高出幾個數量級。透過變溫電導率量測觀察到奈米結構MoS2擁有比塊材低的活化能，結合電導率結果可推測MoS2表面有著較材料內部高的導電特性。由transfer length method (TLM)分析發現MoS2表現出二維的電傳輸特性，並排除可能的接觸電阻效應。MoS2塊材原始表面(non-fresh surface)藉由掃描式穿隧顯微鏡(STM)量測證明了表面具有電子聚集的特性。擁有新撕開的新鮮表面(fresh surface)的塊材從STM量測並無發現表面電子聚集。放置大氣下4個月後由STM量測可得到與原始表面的塊材相同的結果。奈米結構fresh surface的MoS2量測到接近塊材等級的電導率。此外，亦對相近厚度但具有不同電導率的MoS2奈米結構做活化能量測，分析活化能機制與表面態的變化。利用場效應電晶體(FET)量測，可發現fresh surface的MoS2奈米結構相對於non-fresh surface的樣品表現出較高的電子遷移率與較低的電子濃度。推測non-fresh surface的MoS2奈米結構可能存在著較強的表面散射機制。

Surface electron accumulation (SEA) and thickness-dependent electric properties in the molybdenum disulfide (MoS2) two-dimensional (2D) nanostructures have been observed and investigated. The MoS2 nanoflakes fabricated by mechanical exfoliation exhibit several orders of magnitude higher conductivity than their bulk counterparts. The carrier activation energy of nanostructures is lower than that of the bulk counterparts. The transfer length method was used to determine the current transport in MoS2 following a 2D behavior rather than the conventional 3D mode. Scanning tunneling microscopy measurements confirmed the presence of surface electron accumulation (SEA) in this layer material. Notably, the pronounced n-doping characteristic can be easily removed by producing a fresh surface through mechanical exfoliation. Long-term exposure to air can transform the intrinsic fresh surface into a metallic-like surface, indicating that SEA is not inherent. The FET measurement indicates that the MoS2 nanoflakes with fresh surface exhibit higher mobility and lower electron concentration compare to the nanoflakes with non-fresh surface. A more significant surface scattering in the non-fresh MoS2 nanoflakes was proposed.

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