因奈米級侷限水膜誘發電洞摻雜的單層石墨烯於二氧化矽基板表面的奈米級摩擦力學之特性

Frictional characteristics of nano-confined water-mediated hole-doped single-layer graphene on silica surface

朱恩德(Chu En-De)

指導教授 ： 邱顯智

國立臺灣師範大學/理學院/物理學系/碩士(2019年)

https://doi.org/10.6345/NTNU201901165

摘要

我們研究了因奈米級侷限水膜誘發電洞摻雜的單層石墨烯於二氧化矽基板表面的奈米級摩擦力學性質。我們利用原子力顯微鏡量測電洞摻雜的表面電位以及表面摩擦大小時，並且在表面電位圖與摩擦訊號圖觀察到因奈米級水膜存在而形成的多邊形區域，而且多邊形區域比其四周區域擁有較高的表面電位以及較大的摩擦訊號。存在於單層石墨烯與二氧化矽基板間的的奈米級水膜會使單層石墨烯的電洞摻雜效應，因而產生帶正電且親水性的表面。而親水性的表面則有利於大氣中水分子吸附。因此，當我們在量測摩擦力過程時，針尖與單層石墨烯表面間有奈米級毛細水橋的形成，導致表面的摩擦力與表面吸附力的增加。此外，由於不同表面的濕潤性質，我們分別在多邊形區域內外發現摩擦力對速率關係呈現正相關與負相關。未來，我們若是能調控單層石墨烯與粗糙二氧化矽基板之間奈米級水膜的數量或是液體分子的極性，則可進一步操控單層石墨烯表面摩擦特性。我們的實驗結果將可能應用於微奈米機電系統中的元件中。

關鍵字

單層石墨烯 ； 奈米級水膜 ； 原子力顯微鏡 ； 奈米磨潤力學

並列摘要

We have investigated the frictional properties of single-layer graphene (SLG) coated rough silica substrate under the influence of nano-confined hydration layer underneath SLG. Through the friction and surface potential measurements by atomic force microscopy (AFM), we found polygonal features in AFM images of SLG-protected silica surface that exhibit simultaneously larger friction and higher surface potential as compared to their surrounding areas due to water layers confined under SLG. Nano-confined water layers at the SLG-silica interface can induce the hole-doping effect in SLG, resulting in a more positively-charged and hydrophilic surface that favors adsorption of ambient water molecules. Therefore, during friction measurements, nanoscale capillary bridges can form within the interstices of AFM probe-SLG contact, leading to larger adhesion and friction. The friction forces were found to respectively have negative and positive dependence on the sliding velocity inside and outside the polygonal regions due to different surface wettability. Hence, it is possible to manipulate the frictional properties of SLGcoated silica by the amount of hydration layer confined underneath SLG. Our results may find applications in friction control for future nano-devices.

並列關鍵字

Single-Layer Graphene ； Nano-Confined Water ； Atomic Force Microscopy ； Nanotribology

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