單層六方氮化硼中穿隧摩擦電荷動態之研究

Abstract

在本研究工作中，我們探討了單層六方氮化硼在帶電摩擦過程中，穿隧摩擦電荷注入、儲存與耗散現象。我們使用原子力顯微鏡(atomic force microscope, AFM)操控帶有偏壓的導電式探針在單層六方氮化硼表面進行帶電摩擦，並在摩擦結束後立刻使用克爾文探針顯微鏡(Kelvin probe force microscope, KPFM)量測摩擦區域表面電位的變化。我們發現在帶電摩擦的過程中，導電式探針上的電荷會透過穿隧摩擦起電效應(tunneling triboelectric effect, TTE)由六方氮化硼的結構缺陷穿隧並儲存在下方的空氣層與二氧化矽基板中，造成摩擦區域的表面電位發生變化，而變化的程度可以透過摩擦時施加在探針上的偏壓調控。我們還發現，摩擦區域的表面電位變化會隨著量測KPFM的次數增加而下降，這表示量測KPFM的過程中儲存在摩擦區域的穿隧電荷會反向穿隧被導電探針帶走，導致穿隧電荷逐漸消散。此外，穿隧電荷隨量測次數的消散動態行為會符合自然指數衰退的模型。最後，我們使用氬電漿轟擊以增加六方氮化硼的結構缺陷，並發現帶有較多缺陷的樣品在摩擦過後，穿隧電荷的消散會比原始樣品更快。我們的研究揭示了單層六方氮化硼的帶電摩擦特性，使我們更深入了解其作為元件電極保護層的可能性。In this study, we used atomic force microscope (AFM) to manipulate a biased conductive AFM (c-AFM) probe to rub against supported monolayer h-BN. Immediately after rubbing, we measured the surface potential of the rubbed area on h-BN using Kelvin probe force microscope (KPFM). We found that during the rubbing process, charges from the cAFM probe can tunnel through structural defects in h-BN via the tunneling triboelectric effect (TTE) and will be stored in the underlying air gap, leading to changes in the surface potential of rubbed region on h-BN. The variations in surface potential can be controlled by adjusting the electric bias applied to the c-AFM probe during rubbing. We found that the surface potential changes in the rubbed area decreased with the number of repetitive KPFM measurements. This suggests that the TTE charges underneath h-BN can dissipate through reverse tunneling via the c-AFM probe, leading to gradual charge dissipation with repetitive KPFM measurements. The dissipation dynamics follow a natural exponential decay model. Finally, we increased the structural defects in h-BN by argon plasma treatment and found that the dissipation of TTE charges in the defective h-BN samples was faster than that in the pristine ones. Our results reveals the properties of monolayer h-BN under sliding electric contact, enhancing our understanding of its functionality and possibility for applications as surface protective layers.