渦旋光對低維度材料與磁性薄膜異質結構之光電響應增益探討

Abstract

本研究將藉由將拉蓋爾-高斯(Laguerre-Gaussian, LG)光束照射在磁性材料與低維度材料的異質結構上，以探討帶有軌道角動量的渦旋光對其所產生的效應。由於LG光束具有特殊的電場分佈，藉由理論推測可能會與材料表面的電子海進行交互作用進而產生環形電流及垂直磁場。在材料的選擇上我們使用鈷作為鐵磁性材料，而低維度材料是選用具有相近能隙的半導體材料：MoS2及C60來進行探討。首先我們探討Co與MoS2的異質結構，由於在先前的研究中發現在Co/MoS2系統中鈷原子會使MoS2具有特殊的磁各異向性，提供了Co/MoS2異質結構與LG光束間交互作用的可能性。再來我們試著於鈷薄膜中摻入C60薄膜，由先前的研究指出Co與C60會有電子交換行為使得C60會帶有磁性，因此我們便以Co/C60/Co/MoS2異質結構來探討此結構與Co/MoS2異質結構間的差異，進一步研究鐵磁薄膜與低維度材料異質結構對LG光束的響應。最後，我們試著改變鐵磁材料與低維度材料的結構，由層狀堆疊改為合金的結構，探討Co-C60合金薄膜對渦旋光間的響應。研究結果顯示在二硫化鉬上透過蒸鍍法鍍上一層鈷薄膜後，會使得該元件對LG光的光電響應更為明顯；另外在Co/C60/Co/MoS2異質結構上發現在鈷薄膜中摻入C60薄膜的多層堆疊結構有著更顯著的光電響應，並且對LG光束也有著更強的反應。另外，在Co-C60合金的實驗中發現，對其照射渦旋光時此合金薄膜的阻值會隨著軌道角動量增加而上升。在物理機制的探討中，我們藉由從電子自旋的疊加態分佈，去探討LG光束所造成的外加磁場對光電響應的影響。This study aims to investigate the effects of Laguerre-Gaussian (LG) beams with orbital angular momentum on heterostructures of magnetic thin films and low-dimensional materials. Firstly, the unique electric field distribution of LG beams suggests a possible interaction with the electron sea on the material's surface, leading to the generation of circular currents and perpendicular magnetic fields. In this experiment, molybdenum disulfide (MoS2) is chosen as the research subject for its excellent carrier conductivity and direct bandgap, which results in significant photoresponse. Recent studies have shown that the interface between MoS2 and cobalt atoms exhibits magnetic anisotropy due to the coupling between cobalt and sulfur atoms in MoS2, providing the potential for interaction with LG beams inCo/MoS2 heterostructures. Additionally, it has been discovered that C60 exhibits electron exchange interaction with cobalt, making C60 ferromagnetic. Moreover, the bandgap of C60 molecules is close to that of MoS2, suggesting that it can be excited by light with similar wavelengths. Therefore, we aim to study the influence of LG beams on the electrical properties of Co-C60 composite structures, as well as the response of Co/C60/Co/MoS2 heterostructures to LG beams. The research results demonstrate that depositing a cobalt thin film onto MoS2 enhances the photoresponse to LG light. Furthermore, it is found that introducing C60 thin films into the cobalt film stack exhibits a more significant photoresponse and a stronger reaction to LG beams. Finally, this study proposes possible physical mechanisms by exploring the impact of the external magnetic field induced by LG beams on the photoresponse based on the superposition distribution of electron spins.