利用臨場電性量測研究硒化銦的表面氧化現象

Study Surface Oxidation of Layered Indium Selenide by Operando Electrical Measurement

陳彥翔(Yen-Hsiang Chen)

指導教授 ： 王偉華 ； 李志浩

國立清華大學/原子科學院/工程與系統科學系/碩士(2021年)

摘要

二維材料具有原子級厚度並且能夠克服短通道效應(short channel effect)成為半導體中熱門的材料。在二維材料中，硒化銦(InSe)相較於過渡金屬硫化物(TMDs)有較高的載子遷移率，但硒化銦在大氣下衰退相當快速，因此，保護硒化銦通道成為重要的議題。
利用乾氧氧化鈍化表面缺陷保護硒化銦為其中一種鈍化方式，為了瞭解乾氧氧化對於硒化銦場效電晶體電性影響，在此論文中，透過量測硒化銦場效電晶體電性隨時間的變化，了解其氧化過程與載子遷移率在乾氧氧化下衰退的程度。隨著氧化時間增加，載子遷移率會衰退、臨界電壓會上升、遲滯現象會下降。經過長時間的氧化(1000分鐘)，硒化銦表面能夠被鈍化，電性不再變化，因此，利用電性變化證明乾氧氧化能鈍化硒化銦表面。另外，我們發現降低氧化溫度能夠降低載子遷移率衰退幅度，在250 K下氧化，電性衰退10 %就能達到鈍化效果，但在300 K下氧化衰退幅度高達30 %。
另外，此論文也討論兩種常用的缺陷產生方式(電漿蝕刻、雷射)對於硒化銦氧化現象的影響。氦氣電漿蝕刻後，硒化銦在氧化過後放在高真空環境下(3 × 10−6 Torr)，將表面附著原子去除，其衰退之載子遷移率可以被恢復，此現象只有在電漿蝕刻樣品發現；將硒化銦曝於雷射下(633 nm)，硒化銦載子遷移率衰退幅度大於未照射雷射之硒化銦，且乾氧氧化鈍化效果也較低，經過1000分鐘氧化後，載子遷移率衰退持續衰退。透過阿瑞尼士方程式(Arrhenius equation)，由變溫載子遷移率衰退時間不同，我們估計出原始硒化銦氧化反應兩階段能障分別為0.21 eV和0.40 eV，經過雷射照射後，反應能障降低為0.08 eV 和 0.17 eV。

關鍵字

硒化銦 ； 氧化 ； 臨場電性量測

並列摘要

Two dimensional (2D) materials are promising materials because of its atomically thin thickness and suppressed short channel effect. Among various 2D semiconductors, layered indium selenide (InSe) shows outstanding electrical properties such as high intrinsic carrier mobility compared to 2D transition metal dichalcogenides (TMDs). However, InSe is very sensitive to ambient environment and shows severe degradation in air, indicating the formation of non-uniform and defective surface of InSe after air-oxidation.
To understand the effect of the surface oxidation, we performed the in-situ electrical measurement of FET. The dynamic oxidation process of InSe was studied by the in-situ electrical measurement, where a positive shift in threshold voltage and a decreasing hysteresis during dry-oxidation process was observed. The mobility of InSe FET preserves its intrinsic high mobility after dry oxidation treatment at 250 K. The change of electrical properties saturates at certain time, and that remains stable in dry oxygen at 300 K. These observations suggest that the controlled surface oxidation method provides a promising strategy for engineering electrical property of InSe semiconductors.
Also, we demonstrate the dry oxidation process on InSe with two kinds of defect engineering method, including argon plasma etching and laser exposure. For InSe with argon etching, the change of mobility is reversible after keep it under 3 × 10−6 Torr for 1000 min to pump the absorbed oxygen out which only occur on InSe with argon plasma etching. For InSe with laser exposure, the InSe FET is more unstable than pristine InSe that the mobility of InSe still degrade after dry oxidation for overnight. And, the energy barrier of oxidation (0.08 and 0.17 eV) also lower than pristine InSe (0.21 and 0.40 eV).

並列關鍵字

Indium Selenide ； Oxidation ； Operando electrical measurement

參考文獻

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