利用同調聲學聲子研究銻烯與雙層二硫化鉬之間的凡得瓦耦合

Abstract

由於接觸電阻直接影響金屬與半導體之間的載子傳播，因此現代半導體技術中這是一個極其重要的物理參數。然而在傳統金屬與二維材料的異質介面中，二維材料作為下一世代取代矽的強力候選人，卻有著極大的接觸電阻，這是由於金屬誘導的能隙Metal-Induced Gap States ,MIGS）和凡得瓦作用(van der Waals interaction)的隧道障壁(tunneling barrier)所導致。半金屬以其獨特的費米能階(Fermi level)的特性應對MIGS的問題。然而，半金屬與2D材料的接觸電阻仍然很高。為了解決這個問題，部分文獻探討了藉由提高接觸金屬與二維材料之間的混成(hybridization)可以有效地降低接觸電阻。而藉由通凡得瓦作用來調變混成大小則為其中一個解決方案。因此若有一個技術可以估計凡得瓦作用的大小將會對這領域的研究帶來很大的影響。 本文，我們報導了一種估算凡得瓦作用的技術。這種技術使用銻烯作為聲學轉換器(acoustic transducer)產生聲學聲子。藉由聲子我們可以測量銻烯與MoS2之間不同厚度的聲學響應。此外，這種技術對振動器的厚度非常敏感。也就是說，通過改變銻烯的厚度，我們可以獲得厚度依賴的聲學響應。最後，經過數值分析，我們得出銻烯與MoS2之間的凡得瓦位勢(van der Waals potential)約為1.5±1.08（eV/nm^2）。使用這種技術，我們可以輕鬆地估算出2D異質結構中存在多大的凡得瓦作用。我們相信這是研究如何在下一代半導體技術中降低接觸電阻的重要印信息。

For the next-generation semiconductor technology, two-dimensional material (2DM) are the most potential ingredients of semiconductor devices. Contact resistance is a critical factor in modern semiconductor technology as it directly impacts carrier injection from metal to semiconductor. While contact resistance between metals and 2D materials is high due to Metal-Induced Gap States (MIGS) and van der Waals tunneling barriers. To deal with MIGS, semimetals meet this issue with their Fermi level characteristics. However, semimetal-2D material contact resistance remains high. To address this, enhancing semimetal-2D material hybridization, potentially through van der Waals interactions, is explored. Utilizing 2D materials as contact metal is a promising approach due to van der Waals bonding. Thus, finding a method to quantify van der Waals interaction between vdW heterostructures like antimonene/MoS2 heterostructures is essential for next-generation semiconductor technology. Here, we reported a method to estimate the vdW interaction between antimonene (2D form of Sb) and MoS2. This technique uses antimonene as an energy transducer to absorb the energy from femtosecond near-UV pulse so that we could initiate the impulsive acoustic vibrations of the vdW heterostructure of antimonene/MoS2. Through varying the thickness of antimonene and by measureing the thickness dependent coherent vibration frequencies, the van der Waals potentials between antimonene and MoS2 can be quantified as around 1.5±1.08 (eV/nm^2) by using parabolic approximation.