鈷/六方氮化硼-異質結構之表面形貌探討
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2023
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由於二維絕緣體材料六方氮化硼 (h-BN) 與塊材結構亦為六方晶體的鈷 (Co) 之晶格結構一致，而且晶格常數的匹配度非常接近，因而此論文專注使用原子力掃描顯微儀 (Atomic Force Microscopy) 研究鈷在六方氮化硼上磊晶成長為薄膜的過程中，其表面形貌如何隨堆疊厚度而演化。本研究使用原子力顯微儀的輕敲模式，分析不同厚度的鈷連續薄膜和鈷微方格在矽基板和六方氮化硼的表面形貌，以及承受不同溫度的高真空熱退火前後的變化。實驗結果顯示，六方氮化硼在濕式轉移於矽基板歷經400度C退火一個小後，可達低於 ±1奈米的表面平整度。鈷薄膜蒸鍍於六方氮化硼，形成平整度約 ±2奈米，經歷400度C退火程序後，會形成較大的奈米島，高低落差為 ±5奈米，橫向尺寸約為數百奈米。此研究顯示，高溫退火對於「鈷/六方氮化硼」的形貌會有非常顯著的影響，這些實驗成果將能夠應用在使用「鈷/氮化硼」異質結構於未來的磁阻元件之中。
Since the two-dimensional insulator material hexagonal boron nitride (h-BN) has the same crystalline structure as the bulk cobalt (Co), which is also hexagonal, and the lattice constants are very closely matched, this thesis focuses on the use of scanning Atomic Force Microscopy (AFM) to study how the surface morphology of cobalt evolves with the thickness of the stack during the process of epitaxial growth of cobalt on hexagonal boron nitride as a thin film. In this study, the tapping mode of an AFM was used to analyze the surface morphology of cobalt continuous films and cobalt micro-squares with different thicknesses on silicon substrates and h-BN, as well as the changes before and after vacuuming thermal annealing at different temperatures. Experimental results show that the surface roughness of h-BN can reach less than ±1 nm after wet transfer to the Si substrate and annealing at 400°C for one hour. The cobalt film is evaporated on h-BN to form a flatness of about ±2 nm. After annealing at 400 degrees C, larger nano-islands will be formed with a height difference of ±5 nanometers and a lateral size of about several hundred nanometers. This research shows that high-temperature annealing significantly affects the morphology of"Co/h-BN". These experimental results will be able to be applied to future magneto resistive devices using "Co/h-BN" heterostructures.
Since the two-dimensional insulator material hexagonal boron nitride (h-BN) has the same crystalline structure as the bulk cobalt (Co), which is also hexagonal, and the lattice constants are very closely matched, this thesis focuses on the use of scanning Atomic Force Microscopy (AFM) to study how the surface morphology of cobalt evolves with the thickness of the stack during the process of epitaxial growth of cobalt on hexagonal boron nitride as a thin film. In this study, the tapping mode of an AFM was used to analyze the surface morphology of cobalt continuous films and cobalt micro-squares with different thicknesses on silicon substrates and h-BN, as well as the changes before and after vacuuming thermal annealing at different temperatures. Experimental results show that the surface roughness of h-BN can reach less than ±1 nm after wet transfer to the Si substrate and annealing at 400°C for one hour. The cobalt film is evaporated on h-BN to form a flatness of about ±2 nm. After annealing at 400 degrees C, larger nano-islands will be formed with a height difference of ±5 nanometers and a lateral size of about several hundred nanometers. This research shows that high-temperature annealing significantly affects the morphology of"Co/h-BN". These experimental results will be able to be applied to future magneto resistive devices using "Co/h-BN" heterostructures.
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六方氮化硼, 原子力顯微鏡, 鈷, 真空退火, 二維材料, h-BN, AFM, Cobalt, Vaccum Annealing, 2D material