請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/88373
標題: | 透過準粒子干涉探討小角度堆疊之雙層二維半導體的域與域壁的電子特性 Quasiparticle Interference study of electronic properties in domains and domain walls of twisted bilayer 2D Semiconductors |
作者: | 黃琬婷 Wan-Ting Huang |
指導教授: | 邱雅萍 Ya-Ping Chiu |
關鍵字: | 掃描穿隧顯微鏡,扭曲雙層的二維過渡金屬硫化物,準粒子干涉,重構,摩爾,應變,域壁, scanning tunneling microscopy,Quasiparticle Interference,twisted bilayer TMDs,moiré,reconstruction,strain,domain wall, |
出版年 : | 2023 |
學位: | 碩士 |
摘要: | 近年來,由於二維過渡金屬硫化物(TMDs)的二維結構和電子性質,使其已成為縮小場效電晶體(FETs)尺寸的廣泛使用材料。雙層二維過渡金屬硫化物在小角度堆疊所產生的晶格重構,進一步的衍生有許多獨特且可調的物理性質值得探討,例如摩爾電位(moiré potential)、超平坦能帶 (flat bands)等。當兩層材料堆疊角度小於3度,扭轉雙層過渡金屬硫化物將會產生重構,導致材料上產生局部性的應變,而使原子有微小的位移以達到更穩定的堆疊狀態。因此,重構將局部地改變層與層之間的距離,進而影響其電子特性。然而,因為域與域壁的尺度是奈米等級,所以量測必須具備原子級的解析度,來觀察從域至域壁的電性變化。因此,將透過具有可以直接獲取局域性電子結構的準粒子干涉,研究從域至域壁的電性變化。本研究使用低溫掃描穿隧顯微與能譜技術(LT-STM/S)測量小角度堆疊之雙層二硫化鎢表面上的準粒子干涉現象,並進一步探討能帶結構資訊。我們成功地在0度與小角度堆疊下量測到準粒子干涉的圖形。透過分析0度的雙層二硫化鎢上的散射圖形的週期隨偏壓的變化,從偏壓-2.08 V至-1.75 V,散射圖形的週期從1奈米增加至1.7奈米。此趨勢符合能谷隨能量的變化。因此,我們確定了在價帶上所量測的圖形是Γ谷谷內散射形成的圖形,此結果符合文獻的量測到的散射圖形。藉由在0度的量測結果確認在小角度堆疊下量測的圖形是準粒子干涉現象所造成的。實驗結果顯示在小角度堆疊的XM與MX的區域所量測到的散射圖形的週期是相同的,其週期大約是1.6奈米,無發現兩區域的能帶結構有差異。另外,散射圖形在域壁上的週期大約是1.9奈米,相較於XM/MX的區域增加0.3奈米,代表在相同能量下,域壁能帶結構的Γ谷與XM/MX區域之Γ谷相比,其寬度較窄。域壁的能帶結構的變化可歸因於在小角度的堆疊下,雙層二硫化鎢發生晶格重構,使域壁上產生應變(strain),進而使上下層結構不對稱,且導致層間距離增加,進而影響了域壁的Γ谷,使散射圖形的週期增加0.3奈米。本研究提供了小角度堆疊之雙層二維半導體的准粒子干涉圖形如何受到扭曲雙層二硫化鎢的影響,以及解釋在域與域壁的準粒子干涉圖形變化的機制。 In recent years, two-dimensional transition metal dichalcogenides (TMDs) have become widely used materials for scaling the size of field-effect transistors (FETs) because of their two-dimensional structure and electronic properties. In addition, the lattice reconstruction caused by twisted bilayer TMDs further leads to many unique and tunable physical properties worth discussing, such as moiré potential, flat bands, etc. When the relative angle between two layers is small (< 3°), the structure of twisted bilayer transition metal dichalcogenides (tb-TMDs) undergoes a reconstruction process, which generates localized strain and adjusts atom arrangement to achieve a more stable stacking. Hence, the reconstruction will locally change the distance between layers and affect their electronic properties. However, since the domains and domain walls scale are on the nanometer level, measurements must have an atomic-level resolution to observe the electrical changes from domains to domain walls. Therefore, quasiparticle interference, which can directly obtain localized electronic structure, can be used to investigate the electrical changes from domains to domain walls. In this work, we used low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/S) to measure quasiparticle interference (QPI) in different domains of the twisted bilayer WS2 and further investigate the band structure information. We successfully measured the scattering patterns on 0° and small-angle stacking bilayer WS2. By analyzing the variation of the wavelength of the scattering patterns on 0° bilayer WS2 with bias voltage ranging from -2.08 V to -1.75 V, we observed an increase in wavelength from 1 nm to 1.7 nm. This trend is consistent with the change in Γ-valley. Therefore, we determined that the patterns measured at valence bands arise from the intravalley scattering in Γ-valley. This result is consistent with previous literature. Comparing with the measurement results of 0° region, we identified that the patterns measured on small-angle stacking are quasiparticle interference. Experimental results showed that the wavelength of the scattering patterns measured in XM and MX stacking regions were the same, which is approximately 1.6 nm. No difference was observed in the band structures of the two regions. In addition, the wavelength of the scattering patterns on the domain wall was approximately 1.9 nm, increasing by 0.3 nm compared to that in the XM/MX region, indicating that the Γ-valley of the band structure on the domain wall was narrower than that of the Γ-valley in the XM/MX region at the same energy. The variation in the band structure of the domain wall can be attributed to lattice reconstruction in small-angle twisted bilayer WS2, resulting in strain on the domain wall. The reconstruction increases the interlayer distance, affecting the band structure of the domain wall, leading to an increase in the wavelength of the scattering patterns. This study provides how scattering patterns of QPI are affected by twisted bilayer WS2 and the possible formation mechanism of variations in scattering patterns of QPI in twisted bilayer WS2. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/88373 |
DOI: | 10.6342/NTU202302257 |
全文授權: | 未授權 |
顯示於系所單位: | 物理學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-111-2.pdf 目前未授權公開取用 | 2.35 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。