飛秒雷射退火對二硫化鉬缺陷優化之影響

Abstract

二維材料在現今對於人類發展半導體及其相關科技都指向著一個全新的方向及材料。隨著現代的科技的日新月異，地球上越來越多淺在的能源及材料被科學家們發現及利用，其中又以過渡金屬二硫化合物（TMDC）被認為是最有可能應用於積體電路的材料，其能隙大小最適合用來做場效電晶體（FET）中的通道。在經過對於過渡金屬二硫化合物的探索後，目前有兩種做適合做為通道的材料：二硫化鉬（MoS2）及二硫化鎢（WS2），兩者之間的差異在製作成場效電晶體後開、關狀態下電流大小各有其優點。本次實驗中我們選定二硫化鉬作為材料，在製作及準備的過程中利用氣相沉積法（CVD）讓二硫化鉬生長在不同材質的基板上，讓其構成單層二硫化鉬平面，在矽（Si）單層與二硫化鉬單層之間只有非常微弱的凡德瓦力（Van der Waals）[1]去支撐層與層之間相連，但是在生長的過程中可能因為其他外在因素而造成二硫化鉬表面缺陷（defect）的產生，進而在學術研究或生產半導體產品時得到錯誤的數據及成品。在本篇論文中我們利用飛秒雷射（Femtosecond laser） 聚焦在MoS2表面或體積上，產生高能量密度的熱源，使材料受熱區域溫度升高，並且在冷卻過程中產生新的晶體結構，進而優化具有缺陷的MoS2。因為雷射的脈衝寬度非常的短，所以如果使用此種技術對樣品進行加工，可以在極短的時間之內產出大量的成品，因此可以避免材料因長時間暴露在高溫下而引起的其他變化，也因為這個實驗有許多不同的參數可以做調整：可以調整功率的高低進而加工不同傷害極限值的材料；可以控制不同的加工範圍大小進而加工不同尺寸的樣品；可以繪製不同的加工圖形讓加工的可塑性更高。本次實驗我們使用光致發光（Photoluminescence）及拉曼（Raman）作為檢測系統，在光致發光過程中通常會用一種能量較高的光源，如雷射，照射到樣品上，使其電子遷移到高能態。當這些電子回到低能態時，會釋放出能量，並且產生輻射，從而產生發光現象。然而拉曼的部分是因為拉曼光譜學可以檢測出其中的缺陷。這些缺陷會對應特定的拉曼光譜訊號，因此可以通過對拉曼光譜圖進行分析，進而定性和定量分析二維材料中的缺陷。

Two-dimensional materials have ushered humanity into a novel realm of semiconductor development and related technologies. With the rapid evolution of modern science and technology, an increasing number of latent energy sources and materials are being discovered and harnessed by scientists. Among these, transition metal dichalcogenides (TMDCs) stand out as a highly promising material for integrated circuits, with their bandgap ideally suited for channel applications in field-effect transistors (FETs).Following explorations into transition metal dichalcogenides, two materials have emerged as suitable channel candidates: molybdenum disulfide (MoS2) andtungsten disulfide (WS2). The distinction between them lies in the current magnitude during the on-off states of the fabricated field-effect transistors, each possessing unique advantages. For this experiment, MoS2 was selected as the material, and chemical vapor deposition (CVD) was employed in the fabrication and preparation process to grow MoS2 on different substrate materials, forming a monolayer MoS2 plane. The interaction between the silicon (Si) monolayer and the MoS2 monolayer is supported by weak van der Waals forces, although defects may arise during growth due to external factors, leading to erroneous data and end products in academic research or semiconductor production.In this paper, we employ femtosecond laser focusing on the MoS2 surface or volume, generating a high-energy-density heat source that elevates the temperature in the targeted region. During the cooling process, new crystal structures are formed, optimizing defective MoS2. The ultra-short pulse duration of the laser facilitates rapid sample processing, mitigating material alterations resulting from prolonged exposure to high temperatures. The experiment offers multiple adjustable parameters: power levels can be modified to process materials with varying damage thresholds; processing dimensions can be controlled for different sample sizes; diverse processing patterns can be drawn to enhance malleability.Photoluminescence and Raman spectroscopy serve as the detection systems for this experiment. Photoluminescence involves illuminating the sample with a high-energy light source, such as a laser, causing electrons to transition to higher energy states. As these electrons return to lower energy states, they release energy, resulting in radiation and luminescence. Meanwhile, Raman spectroscopy is employed to detect defects, as specific Raman signals correspond to particular defects. By analyzing the Raman spectroscopic data, qualitative and quantitative assessments of defects in the diode can be conducted.