利用原子力顯微術探討環境溫度與溼度對單層石墨烯表面吸附性質的影響

Abstract

在本實驗中，我們探討了溫度和相對濕度對二氧化矽探針在單層石墨烯（Single Layer Graphene, SLG）表面吸附力的影響，並比較針尖為四面體形狀的探針與球型探針在吸附力量測中的穩定性。實驗中，我們利用變溫系統調整樣品與探針的溫度，並使用濕度控制系統調整相對濕度，確保環境參數穩定可控。並透過原子力顯微鏡（Atomic Force Microscopy, AFM）量測，我們觀察到四面體探針的吸附力數據波動顯著且無明確趨勢，而球型探針則呈現穩定且一致的吸附力結果，這是因為球型探針與樣品的接觸面較大所導致。此外，隨溫度從室溫上升至 100°C時，因毛細水橋中的水分子會隨著溫度升高而逐漸蒸發，導致吸附力逐漸減小；而當溫度超過 125°C 時，環境溫度已超過水的沸點，使水橋無法穩定存在，因此吸附力趨於穩定。再者，當相對濕度增加時，有利於水橋形成，使毛細力增強，導致吸附力顯著增大。我們的研究結果揭示了單層石墨烯與二氧化矽探針間的吸附力在不同溫度和濕度條件下的變化特性，這些結果未來可能可以應用於微機電系統（MEMS）和奈米機電系統（NEMS）的性能優化。

In this study, we investigated the effects of temperature and relative humidity on the adhesion force between silica atomic force microscope (AFM) probes and single-layer graphene (SLG) surfaces. The stability of adhesion force measurements using pyramidal and spherical AFM probes and compared. By employing a temperature-controlled system to adjust the sample and probe temperatures, and a humidity control system to regulate the relative humidity, we ensured stable and controllable environmental parameters throughout the experiments. Using AFM, we observed that the adhesion force data obtained with pyramidal probes exhibited significant fluctuations without a discernible trend as the temperature increased. On the contrary, when spherical probes were used, the measured adhesion force not only demonstrated clear dependence on environmental humidity and temperature, but also was highly repeatable. This difference is attributed to the larger contact area between the spherical probe and the sample surface. Furthermore, as the temperature increased from room temperature to 100°C, the adhesion force between the spherical AFM probe and SLG surface gradually decreased due to the evaporation of water molecules in the nanoscale capillary bridges formed at the AFM probe-SLG contact. When the temperature exceeded 125°C, surpassing the boiling point of water, the capillary bridges could no longer stably exist, resulting in a stabilization of the adhesion force. Additionally, increasing the relative humidity facilitated the formation of capillary bridges, enhancing capillary forces and leading to a significant increase in adhesion force between the AFM probe and SLG surface. Our findings confirm that temperature and relative humidity have a significant influence on adhesion forces, and that spherical probes provide higher stability in adhesion force measurements. These results offer a theoretical foundation for controlling surface adhesion forces at the nanoscale and may be applied to optimize the performance of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS).