以飛秒雷射剝蝕過渡金屬二硫化物

Study of Femtosecond-Laser Ablation on Transition Metal Dichalcogenides (TMDs)

陳思樺(Sih-Hua Chen)

指導教授 ： 羅志偉

國立交通大學/理學院/電子物理系所/碩士(2020年)

摘要

在本論文中我們研究過渡金屬二硫化物以中心波長 800 nm，單發雷射脈衝剝蝕下 的剝蝕閥值。介電材料的崩潰在閥值通常會有著很極端的表現，明確表示出物質在高 激發下的狀態。我們找到了初成長的二硫化鉬在 110 fs 時剝蝕閥值約為 4 nJ/μm2，而在 70 fs 時為 3 nJ/μm2，初成長二硫化鎢在 1083 fs 時剝蝕閥值為 4.48 nJ/μm2，而在 90 fs 時 為 2.07 nJ/μm2。而轉印的樣品結果顯示有著更高的閥值。本研究也利用原子力顯微鏡 (AFM)，拉曼光譜 (Raman) 及光致螢光光譜 (PL) 來了解飛秒雷射剝蝕後的表面形貌及 晶體結構的改變。研究過渡金屬二硫化物的剝蝕閥值與脈衝寬度的關係可以說明非線 性載子的產生與鬆弛，尤其是多光子游離、穿隧游離及雪崩游離的規則。

關鍵字

飛秒雷射剝蝕 ； 過渡金屬二硫化物

並列摘要

In this study, we investigate the ablation threshold of transition metal dichalcogenides (TMDs) induced by a single femtosecond laser pulse. Dielectric breakdown of materials of- ten exhibits a very sharp thresholding behavior, indicating a well-defined material status in the strong excitation regime. Ablation threshold was found around 3 nJ/μm2 at 110 fs and 4 nJ/ μm2 at 70 fs for as-grown MoS2, and 2 nJ/μm2 at 90 fs and 4.5 nJ/μm2 at 1100 fs of WS2, while transferred samples show higher thresholds. We have also performed extensive AFM, Raman, and PL characterizations of change in material morphology and structure after the laser expo- sure. Studying ablation threshold as a function of pulse duration will elucidate the nonlinear carrier generation and relaxation dynamics within TMDs, especially the roles of multiphoton ionization, tunneling ionization, and avalanche ionization.

並列關鍵字

femtosecond laser ablation ； transition metal dichacholginides ； TMDs

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