具胺基酸摻雜二硫化鎢量子點的光電特性

本論文利用微波合成法來製備二硫化鎢量子點，其優點為快速並且大量的製作出二硫化鎢量子點，利用胺基酸摻雜提高螢光強度，其中精胺酸摻雜使螢光強度約提高18.2 倍。經由穿透是顯微鏡確認其粒徑大小並由X 光射線光電子能譜確認二硫化鎢量子點的化學鍵結。我們在電學特性研究上觀察到二硫化鎢量子點具有遲滯的現象，並且遲滯現象會隨著胺基酸摻雜濃度增加而增強。利用背閘電流-電壓測量發現製備出的二硫化鎢量子點為p 型摻雜，測量二硫化鎢量子點照射低波段雷射前後的電流-電壓曲線圖，發現二硫化鎢量子點具有負光電導的現象。進一步討論真空下、不同氣體、不同施加電壓範圍以及環境濕度下對於二硫化鎢量子點遲滯現象的影響，發現在真空中、窄的電壓範圍以及低環境濕度下，二硫化鎢量子點的遲滯現象會快速衰減，而在寬的電壓範圍以及高環境濕度下，二硫化鎢的遲滯現象則增強。推論二硫化鎢量子點的遲滯現象機制是由於吸附在二硫化鎢表面的水氣以及內部陷阱態所產生並且照射低波段雷射會產生水氣脫附的行為。

關鍵字

二硫化鎢；過渡金屬二硫化物；量子點；遲滯現象；負光電導現象；氮掺雜

並列摘要

In this research,a microwave synthesis method was used to prepare tungsten disulfide quantum dots (WS2 QDs), which has the advantages of rapid and large-scale production of WS2 QDs. The WS2 QDs was further doped with amino acid to increase its fluorescence intensity.Here, the use of arginine as dopant greatly enhances the fluorescence intensity of WS2 QDs demonstrating an 18.2 fold increase. The quantum dot size and chemical structure of WS2 QDs were confirmed using transmission electron microscope (TEM) and X-ray photoelectron spectroscope, respectively. By investigation of the electrical properties of WS2 QDs, a hysteresis phenomenon was observed. Here, the hysteresis increases with the increase in the amino acid dopant concentration. The back-gate-current-voltage measurement demonstrates that the prepared WS2 QDs is p-type. The current-voltage curves before and after the low-band laser irradiation of WS2 QDs were also measured. It was also found that the WS2 QDs displays a negative photoconductivity (NPC). Investigations of the effects of vacuum, ambient humidity, different gases, and different applied voltage ranges on the hysteresis of WS2 QDs were also gathered. It is found that the hysteresis of WS2 QDs in vacuum showed a narrow voltage range while it decays rapidly at low ambient humidity. On the other hand, the hysteresis of bulk WS2 is enhanced over a wide voltage range and high ambient humidity. It is inferred that the hysteresis mechanism of WS2 QDs is caused by the moisture adsorbed on the surface of WS2 and the existence of the internal trap state, and the exposure from low-band laser irradiation will cause water-gas desorption.