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。

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).

1. Moore, G.E., “Cramming more components onto integrated circuits.” 1965, McGraw-Hill New York, NY, USA:.
2. Novoselov, K.S., et al., “Electric field effect in atomically thin carbon films. ”Science, 2004. 306(5696): p. 666-669.
3. Ajayan, P., P. Kim, and K. Banerjee, van der Waals materials. Physics Today, 2016. 69(9): p. 38.
4. Bandurin, D.A., et al., “High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe.” Nature Nanotechnology, 2017. 12(3): p. 223.
5. Schwierz, F., J. Pezoldt, and R. Granzner, “Two-dimensional materials and their prospects in transistor electronics. ”Nanoscale, 2015. 7(18): p. 8261-8283.
6. Savitskii, P., Z. Kovalyuk, and I. Mintyanskii, “Space‐charge region scattering in indium monoselenide.” Physica Status Solidi (a), 2000. 180(2): p. 523-531.
7. Lei, S., et al., “Evolution of the electronic band structure and efficient photo-detection in atomic layers of InSe.” ACS Nano, 2014. 8(2): p. 1263-1272.
8. Ma, D.W., et al., “The role of the intrinsic Se and In vacancies in the interaction of O2 and H2O molecules with the InSe monolayer.” Applied Surface Science, 2018. 434: p. 215-227.
9. Guo, Y., et al., “Defects and oxidation of group-III monochalcogenide monolayers.” The Journal of Chemical Physics, 2017. 147(10): p. 104709.
10. Wei, X., et al.,“ First-principles study of the surface reparation of ultrathin InSe with Se-atom vacancies by thiol chemistry.” Applied Surface Science, 2019. 475: p. 487-493.
11. Ho, P.H., et al.,“ High-mobility InSe transistors: The role of surface oxides.” ACS Nano, 2017. 11(7): p. 7362-7370.
12. Imai, K., et al., “Phase diagram of In-Se system and crystal growth of indium monoselenide.” Journal of Crystal Growth, 1981. 54(3): p. 501-506.
13. Zhao, G.-Y., et al., “Recent progress on irradiation-induced defect engineering of two-dimensional 2H-MoS2 few layers.” Applied Sciences, 2019. 9(4): p. 678.
14. Liang, Q., et al., “Defect engineering of two-dimensional transition-metal dichalcogenides: applications, challenges, and opportunities.” ACS Nano, 2021. 15(2): p. 2165-2181.
15. Kittel, C., P. McEuen, and P. McEuen, Introduction to solid state physics. Vol. 8. 1996: Wiley New York.
16. Kaasbjerg, K., K.S. Thygesen, and K.W. Jacobsen, “Phonon-limited mobility in n-type single-layer MoS2 from first principles.” Physical Review B, 2012. 85(11): p. 115317.
17. Yu, Z., et al., “Analyzing the carrier mobility in transition‐metal dichalcogenide MoS2 field‐effect transistors.” Advanced Functional Materials, 2017. 27(19): p. 1604093.
18. Ong, Z.-Y. and M.V. Fischetti, “Mobility enhancement and temperature dependence in top-gated single-layer MoS2.” Physical Review B, 2013. 88(16): p. 165316.
19. Hwang, E., S. Adam, and S.D. Sarma,“ Carrier transport in two-dimensional graphene layers.” Physical Review Letters, 2007. 98(18): p. 186806.
20. Radisavljevic, B. and A. Kis, “Mobility engineering and a metal–insulator transition in monolayer MoS2. ”Nature Materials, 2013. 12(9): p. 815-820.
21. Ghatak, S., A.N. Pal, and A. Ghosh, “Nature of electronic states in atomically thin MoS2 field-effect transistors.” ACS Nano, 2011. 5(10): p. 7707-7712.
22. Guo, Y., et al., “Charge trapping at the MoS2-SiO2 interface and its effects on the characteristics of MoS2 metal-oxide-semiconductor field effect transistors.” Applied Physics Letters, 2015. 106(10): p. 103109.
23. Cho, K., et al., “Electric stress-induced threshold voltage instability of multilayer MoS2 field effect transistors.” ACS Nano, 2013. 7(9): p. 7751-7758.
24. Kaushik, N., et al., “Reversible hysteresis inversion in MoS2 field effect transistors.” npj 2D Materials and Applications, 2017. 1(1): p. 1-9.
25. Baker, M.J., C.S. Hughes, and K.A. Hollywood, Raman spectroscopy. Biophotonics: Vibrational Spectroscopic Diagnostics, 2016.
26. Baclayon, M., G. Wuite, and W. Roos,“ Imaging and manipulation of single viruses by atomic force microscopy.” Soft Matter, 2010. 6(21): p. 5273-5285.
27. Jansen, H., et al., “A survey on the reactive ion etching of silicon in microtechnology. ”Journal of Micromechanics and Microengineering, 1996. 6(1): p. 14.
28. Cardinaud, C., M.-C. Peignon, and P.-Y. Tessier, “Plasma etching: principles, mechanisms, application to micro-and nano-technologies.” Applied Surface Science, 2000. 164(1-4): p. 72-83.
29. https://en.wikipedia.org/wiki/Atomic_radii_of_the_elements_(data_page).
30. Xiao, K., A. Carvalho, and A.C. Neto, “Defects and oxidation resilience in InSe. ”Physical Review B, 2017. 96(5): p. 054112.
31. Kistanov, A.A., et al., “Atomic-scale mechanisms of defect- and light-induced oxidation and degradation of InSe.” Journal of Materials Chemistry C, 2018. 6(3): p. 518-525.
32. Cai, Y., G. Zhang, and Y.-W. Zhang, “Charge transfer and functionalization of monolayer InSe by physisorption of small molecules for gas sensing. ”The Journal of Physical Chemistry C, 2017. 121(18): p. 10182-10193.
33. Shi, L., et al., “Oxidation mechanism and protection strategy of ultrathin Indium Selenide: Insight from Theory.” The Journal of Physical Chemistry Letters, 2017. 8(18): p. 4368-4373.
34. Liu, Y., P. Stradins, and S.H. Wei, “Air passivation of chalcogen vacancies in two‐dimensional semiconductors.” Angewandte Chemie, 2016. 128(3): p. 977-980.
35. Tang, C., et al.,“ Low temperature liquid phase growth of crystalline InSe grown by the temperature difference method under controlled vapor pressure.” Journal of Crystal Growth, 2018. 495: p. 54-58.
36. Castellanos-Gomez, A., et al.,“ Laser-thinning of MoS2: on demand generation of a single-layer semiconductor.” Nano Letters, 2012. 12(6): p. 3187-3192.
37. Chow, P.K., et al., “Defect-induced photoluminescence in monolayer semiconducting transition metal dichalcogenides.” ACS Nano, 2015. 9(2): p. 1520-1527.
38. Lin, Z., et al., “Defect engineering of two-dimensional transition metal dichalcogenides.” 2D Materials, 2016. 3(2): p. 022002.
39. Nan, H.Y., et al., “Producing air-stable InSe nanosheet through mild oxygen plasma treatment.” Semiconductor Science and Technology, 2018. 33(7).
40. Cheshev, D., et al., “Patterning GaSe by high-powered laser beams.” ACS Omega, 2020. 5(17): p. 10183-10190.
41. De la Cruz, R., et al., “Positrons and electron-irradiation induced defects in the layered semiconductor InSe.” Applied Physics A, 1992. 54(2): p. 147-151.
42. Zhao, Q.H., et al., “The role of traps in the photocurrent generation mechanism in thin InSe photodetectors.” Materials Horizons, 2020. 7(1): p. 252-262.
43. Arora, H., et al., “Effective hexagonal boron nitride passivation of few-layered InSe and GaSe to enhance their electronic and optical properties.” ACS Applied Materials & Interfaces, 2019. 11(46): p. 43480-43487.
44. He, T., et al., “Etching techniques in 2D materials. ”Advanced Materials Technologies, 2019. 4(8): p. 1900064.