| 摘要: | 近年來，二維(2D)材料因其優異的材料特性，包括原子層厚度、尺寸縮小時的高遷移率以及可控能帶結構，而受到廣泛關注和研究，使其被認為是下世代半導體的關鍵候選材料。其中，過渡金屬二硫化物(TMDs)中的二硫化鉬(MoS2)已得到了廣泛的研究，其具有高機械強度、良好熱穩定性與高載子遷移率，在光感應、邏輯電路元件以及高頻通訊等領域都具有廣泛的應用前景。
單層二硫化鉬具有約1.85電子伏特(eV)的半導體能隙，可透過化學氣相沉積法(CVD)製備高品質、大面積且均勻的連續膜，從而提高了其在半導體工業中的前瞻性。由於晶體晶格匹配性的機制，過去習用藍寶石基板於合成二硫化鉬，而後續仍須要透過轉印製程將其脫附基板並堆疊至目標基材(如氧化矽、氮化矽)上。但這一過程會引入高分子殘留、材料皺褶和破洞等眾多缺陷，而劣化其電性。因此，直接在絕緣基材上進行合成具有重要性。傳統的CVD方法還存在一些局限性，例如生長位置不可控、材料尺寸不均一等問題。
因此，在本研究中，我們提出了以金作為異質成核點位的高度可控晶體生長方法，藉由反應能障上的差異，可以於氧化矽基板上預訂的成核點位生長出結晶尺寸為10微米的單層二硫化鉬。透過光致發光(PL)分析，我們發現這些晶體具有半高寬為61毫電子伏特(meV)的高結晶性。此外，在拉曼光譜和光致發光的製圖檢測(Mapping)中顯示，這些單晶為單層且具有高均勻度與結晶性。利用這種方法，我們可以獲得均一尺寸且大面積地單晶二硫化鉬點陣列(50×50)，隨後進行閘極、汲極和源極的製作，從而製備出二維場效應電晶體。此一方法避免了轉印及電晶體區蝕刻步驟，並且相容於目前半導體製程，大幅減少製程複雜性及成本。
;In recent years, two-dimensional (2D) materials have garnered significant attention and research interest due to their exceptional material properties, including atomic layer thickness, high mobility at reduced dimensions, and tunable band structures. These attributes position 2D materials as promising candidates for next-generation semiconductor technologies. Among these materials, molybdenum disulfide (MoS2) within the transition metal dichalcogenides (TMDs) group has been extensively studied. MoS2 exhibits high mechanical strength, excellent thermal stability, and high carrier mobility, making it highly suitable for applications in photodetection, logic circuits, and high-frequency communications.
Monolayer MoS2 features a semiconductor bandgap of approximately 1.85 eV and can be synthesized into high-quality, large-area, and uniform continuous films through chemical vapor deposition (CVD). This capability enhances its prospects in the semiconductor industry. Traditionally, sapphire substrates have been employed for MoS2 synthesis due to the crystal lattice matching mechanism. However, subsequent processes necessitate the transfer of the MoS2 layer from the sapphire substrate to target substrates such as silicon dioxide (SiO2) or silicon nitride (Si3N4). This transfer introduces numerous defects, including polymer residues, wrinkles, and cracks, which degrade the material′s electrical properties. Consequently, synthesizing MoS2 directly on insulating substrates is of significant importance. Traditional CVD methods have limitations, such as uncontrollable growth locations and non-uniform material sizes.
Therefore, in this study, we propose a highly controllable crystal growth method using gold as a heterogeneous nucleation site. By exploiting differences in reaction energy barriers, we can grow monolayer MoS2 crystals with a size of 10 micrometers at predetermined nucleation sites on a SiO2 substrate. Photoluminescence (PL) analysis reveals that these crystals exhibit high crystallinity with a full width at half maximum (FWHM) of 61 meV. Additionally, Raman spectroscopy and PL mapping indicate that these single crystals are monolayers with high uniformity and crystallinity. Using this method, we can achieve uniform-sized and large-area single-crystal MoS2 arrays (50×50), subsequently fabricating gate, drain, and source electrodes to produce two-dimensional field-effect transistors (FETs). This method avoids transfer and transistor area etching steps, is compatible with current semiconductor processes, and significantly reduces process complexity and cost. |
