使用接觸式原子力顯微鏡在石墨烯/二硫化鉬異質結構上製造圖案化的光致螢光

Abstract

不同二維材料的堆疊會引起光電特性的變化。然而，操縱圖案化的多層二維材料異質結構仍然具有挑戰性。因此，在這項研究中我們使用原子力顯微鏡對多層二維材料異質結構進行了圖案化處理，並進行表面形貌以及光致螢光的量測。應用不同的正向力大小，得以去除石墨烯上的殘留PMMA或是二硫化鉬上的石墨烯。當探針的正向力大小控制在110 nN ~ 200 nN的範圍內，可以有效清除石墨烯表面殘留的PMMA，使得表面粗糙度從平均15 nm下降至平均3 nm。當正向力大小介於200 nN與330 nN之間，石墨烯/二硫化鉬異質結構的石墨烯層會有破碎的現象，而在此範圍內其正向力與破碎程度呈現正相關。當正向力大小大於330 nN，石墨烯/二硫化鉬異質結構的絕大部分石墨烯層會被去除，僅殘存零星的石墨烯碎片。同時，石墨烯/二氧化矽上殘留了93％的石墨烯，這意味著二硫化鉬上的石墨烯比二氧化矽上的石墨烯相對容易刮除。而當正向力大小大於660 nN，可以完全去除石墨烯層並保留完整的二硫化鉬層。在轉移石墨烯之後，石墨烯/二硫化鉬異質結構的光致發光波長會有些微紅移的現象。在正向力摩擦之後的光致發光波長會相對於轉移石墨烯後有些許藍移的現象。在石墨烯/二硫化鉬異質結構上製造圖案，並透過光致發光光譜確認在裸露的二硫化鉬區域，其光致發光的光強度為石墨烯/二氧化矽區域的2倍。在表面電位分佈圖中也可以得到在圖案化的區域，表面電位與周圍石墨烯/二硫化鉬區域的電位差約為300 mV。從光學顯微鏡、原子力顯微鏡、拉曼光譜和光致發光光譜中，分別觀察到了PMMA和石墨烯的去除。我們已經成功地使用原子力顯微鏡來改變表面形貌以及圖案化的光致螢光，這將在未來激發更多有趣的研究或應用。

The stacking of different 2D materials will cause the change of optoelectronic properties. However, it is still challenging to manipulate the microscopic patterns of multi-layer 2D material heterostructures. Therefore, in this study we used atomic force microscope (AFM) to reprocess multi-layer 2D material heterostructures to for the engineering of the surface and photoelectric properties. Applying different magnitudes of contact force can remove residual PMMA on graphene or graphene on molybdenum disulfide. When the contact force is controlled in the range of 110 nN ~ 200 nN, the PMMA remaining on the graphene surface can be effectively removed, so that the surface roughness will drop from an average of 15 nm to an average of 3 nm. When the contact force is between 200 nN and 330 nN, the graphene layer of the graphene/molybdenum disulfide heterostructure will be broken, and within this range, the contact force is positively correlated with the degree of breakage. When the contact force is greater than 330 nN, most of the graphene layer of the graphene/molybdenum disulfide heterostructure will be removed, leaving only sporadic graphene fragments. At the same time, 93% of the graphene remains on the graphene/silicon dioxide, which means that the graphene on the molybdenum disulfide is relatively easier to scrape off than the graphene on the silicon dioxide. When the positive force is greater than 660 nN, the graphene layer can be completely removed, and the molybdenum disulfide layer can remain intact. After the graphene is transferred, the photoluminescence wavelength of the graphene/molybdenum disulfide heterostructure will be slightly red-shifted. The photoluminescence wavelength after the action of the contact force will be slightly blue-shifted with respect to the graphene transferred. Patterns on the graphene/molybdenum disulfide heterostructure and confirm through photoluminescence spectroscopy that in the exposed molybdenum disulfide region, the photoluminescence intensity is 2 times that of the graphene/silicon dioxide region. In the surface potential distribution map, it can also be seen that in the patterned area, the potential difference between the surface potential and the surrounding graphene/molybdenum disulfide area is about 300 mV. From optical microscope, atomic force microscope, Raman spectroscopy and photoluminescence spectroscopy, the removal of PMMA and graphene was observed respectively. We have successfully used atomic force microscopy to change the surface topography and patterned photoluminescence, which will stimulate more interesting research or applications in the future.