二維二硫化鎢上金奈米粒子生長之研究

Abstract

二維材料異質結構物理性質的高度可塑性使其具備廣泛的應用前景，而金屬奈米粒子與二維材料組成的異質結構在光電領域、生物醫學和能源轉換等領域展現出巨大的應用潛力。本研究旨在探討金奈米粒子(AuNPs)在二維二硫化鎢(WS2)表面的成長行為、結晶型態以及溫度對凡得瓦壘晶所造成的影響。 我們以超高真空穿透式電子顯微鏡(UHV-TEM)結合超高真空電子束蒸鍍器，藉由控制蒸鍍時間及溫度，對AuNPs在懸空二維WS2表面的原位生長進行系統性控制，並記錄臨場生長過程。最後以影像分析軟體對其較宏觀的成長行為與微觀的結晶型態進行了深度的分析，並與理論所模擬之結果進行對應。 實驗結果顯示，溫度對AuNPs在二維WS2表面的凡得瓦壘晶具有顯著的影響。在室溫條件下，AuNPs傾向以凡得瓦壘晶的二維生長，呈現三角形或六邊形的奈米島；高溫條件下，AuNPs則傾向以三維生長，呈半球狀的奈米顆粒。我們也探討了溫度對AuNPs/ WS2異質結構介面晶格應變效應的影響，根據理論與實驗的比較，凡得瓦壘晶中的晶格應變效應並不顯著，然而溫度對結晶形態的影響仍導致異質結構介面的晶格應變出現些微差異。此外我們也觀察到了AuNPs/ WS2異質結構中因原子間距差異所引起的摩爾紋。在光電導特性的測量方面，我們嘗試了多種研究方法，但在過程中面臨了接觸電阻與量測穩定性等挑戰，需要進一步克服以提高測量精度和穩定性。 總結來說，本研究深入的地探討了室溫及高溫下AuNPs於懸浮二維WS2表面凡得瓦壘晶的成長行為及其結晶型態。這些結果不僅有助於理解異質結構的成長機制，還為光電器件的設計和製作提供了有價值的參考。此外，本研究中所遇到的光電導測量挑戰也為未來研究提供了改進方向。

The high tunability of the physical properties of two-dimensional (2D) material heterostructures endows them with broad application prospects. Heterostructures composed of metal nanoparticles and 2D materials exhibit significant potential in the fields of optoelectronics, biomedicine, and energy conversion. This study aims to investigate the growth behavior, crystalline morphology, and the effect of temperature on the van der Waals epitaxy of gold nanoparticles (AuNPs) on the surface of 2D tungsten disulfide (WS2). Using an ultra-high vacuum transmission electron microscope (UHV-TEM) combined with an ultra-high vacuum electron beam evaporator, we systematically controlled the in situ growth of AuNPs on suspended 2D WS2 surfaces by regulating the deposition time and temperature, and recorded the real-time growth process. Subsequently, we conducted an in-depth analysis of the macroscopic growth behavior and microscopic crystalline morphology using image analysis software, and compared the results with theoretical simulations. The experimental results show that temperature has a significant impact on the van der Waals epitaxy of AuNPs on 2D WS2 surfaces. At room temperature, AuNPs tend to grow in a 2D manner, forming triangular or hexagonal nanostructures; at high temperatures, AuNPs tend to grow in a 3D manner, forming hemispherical nanoparticles. We also explored the effect of temperature on the lattice strain at the AuNPs/WS2 heterostructure interface. Theoretical and experimental comparisons indicate that the lattice strain in the van der Waals epitaxy is not significant; however, the influence of temperature on the crystalline morphology still leads to slight differences in the lattice strain at the heterostructure interface. Additionally, we observed moiré patterns caused by the atomic spacing differences in the AuNPs/WS2 heterostructure. In terms of photoconductivity measurements, we tried various research methods but encountered challenges related to contact resistance and measurement stability, which need to be further addressed to improve measurement accuracy and stability. In summary, this study thoroughly investigates the growth behavior and crystalline morphology of AuNPs on suspended 2D WS2 surfaces under room and high-temperature conditions. These results not only contribute to understanding the growth mechanisms of heterostructures but also provide valuable references for the design and fabrication of optoelectronic devices. Furthermore, the challenges encountered in photoconductivity measurements in this study provide directions for future research improvements.