電阻式記憶體利用其電阻值變化作為記錄訊號之手段，其阻值變化之機制為介電層中絲狀導電通道之形成以及斷裂，導致阻值於高阻態及低阻態間轉換。其特性包含低耗能、高耐久以及資料儲存能力，由於機制與觸突藉由離子濃度變化傳遞訊息方式相似，使其在人工智能技術中扮演重要角色。然而，導電通道是由導電載子累積形成，不同轉換過程中容易因過多載子積累導致元件崩潰，是電阻式記憶體一大隱憂。
過渡金屬二硫化物在二維材料發展中為一大方向，其層狀結構具有多種應用潛力，本研究應用離子嵌入其各層間隙現象做為限制載子進入介電層中之手段，透過於製程中利用電漿輔助可有效降低反應所需要溫度。此外，透過此方法可將過渡金屬二硫化物由常見之水平層狀堆疊轉為垂直堆疊，使載子能更有效沿電場方向嵌入間隙，達到限制載子濃度之目的，並期望延長元件使用壽命以及提升其電性表現，做為未來科技發展時一項構思。

Resistive random-access memory (RRAM) records signals of 0 and 1 by the resistance. It has some advantages like low energy consumption, stable endurance and retention performances. Some categories of RRAMs have the mechanism of changing resistance by the movement of conductive carriers, which is similar to synapse transform message by the diffusion of ions. With this property, RRAM is always seen as a good choice for application in artificial intelligence (AI). However, the migration of carriers in devices might cause the breakdown with nonproper parameters. Some strategies are carried out to reduce the amounts of ions. Transition Metal Dichalcogenides (TMDCs) are interesting materials with lamellar structure. The intercalation is reported happen in the spacing between layers of TMDCs. It shows a novel method of confining ions with this pillar-like structure. With limited ions by TMDCs, the migration of ions is reduced and enhances the lifetime of devices. Moreover, TMDCs fabricated at different temperature will align in certain direction. It seems this kind of application has high potential to improve the performance of RRAMs.

Abstract (Chinese)………………………………………………Ⅰ
Abstract (English)…………………………………………...…..Ⅱ
Contents…………………………………………………………Ⅲ
Figure Caption……………………………………………….….Ⅳ
Chapter 1 Introduction…………………………………………1
1.1 Resistive Random-Access Memory (RRAM)………………………………………1
1.1.1 Conductive-Bridge Random-Access Memories (CBRAMs)………………2
1.1.2 Bilayer RRAM ………………………………………………………………...3
1.2 Transition Metal Dichalcogenides (TMDCs)……………………………………..4
1.2.1 Composition and crystal phases and electronic structure…………………...4
1.2.2 Fabrication process of TMDCs………………………………………………7
1.2.3 Intercalation of metal ions………………………………………………….10
Chapter 2 Motivation…………………………………………...14
Chapter 3 Experimental Design………………………………...16
3.1 Structure design of devices……………………………………………………...16
3.2 Fabrication of MoSe2……………………………………………………………18
3.3 I-V curve measurement…………………………………………………………21
3.4 Analysis…………………………………………………………………………..23
3.4.1 Raman spectroscopy………………………………………………………..23
3.4.2 X-ray photoelectron spectroscopy (XPS)………………………………….23
3.4.3 Energy-dispersive X-ray spectroscopy (EDS)……………………………..24
Chapter 4 Results and Discussion………………………………26
4.1 Performance of RRAM……………………………………………..…………….26
4.1.1 Comparison of alignment direction………………………….……………….26
4.1.2 Comparison of the addition of MoSe2……………………………….……….29
4.1.3 Comparison of different thickness of MoSe2………………………………34
4.1.4 Comparison of different kind of oxide……………………………………..38
4.1.5 Comparison of different kind of electrode…………………………………40
4.2 Mechanism discussion…………………………………………………………43
4.2.1 XPS analysis………………………………………………………………...43
4.2.2 TEM analysis………………………………………………………………..44
4.3 Application……………………………………………………………………..49
4.3.1 Multilevel cell storage………………………………………………………49
4.3.2 Neuromorphic computing………………………………………………….50
Chapter 5 Conclusion and outlook……………………………..53
Chapter 6 Reference…………………………………………….55

1. Song, I.; Park, C.; Choi, H. C., Synthesis and properties of molybdenum disulphide: from bulk to atomic layers. Rsc Advances 2015, 5 (10), 7495-7514.
2. Duerloo, K.-A. N.; Li, Y.; Reed, E. J., Structural phase transitions in two-dimensional Mo-and W-dichalcogenide monolayers. Nature communications 2014, 5 (1), 1-9.
3. Zhao, W.; Pan, J.; Fang, Y.; Che, X.; Wang, D.; Bu, K.; Huang, F., Metastable MoS2: crystal structure, electronic band structure, synthetic approach and intriguing physical properties. Chem.–Eur. J 2018, 24 (60), 15942-15954.
4. Li, Y.; Zhang, K.; Wang, F.; Feng, Y.; Li, Y.; Han, Y.; Tang, D.; Zhang, B., Scalable synthesis of highly crystalline MoSe2 and its ambipolar behavior. ACS applied materials & interfaces 2017, 9 (41), 36009-36016.
5. Chen, W.; Xie, X.; Zong, J.; Chen, T.; Lin, D.; Yu, F.; Jin, S.; Zhou, L.; Zou, J.; Sun, J., Growth and Thermo-driven Crystalline Phase Transition of Metastable Monolayer 1T′-WSe 2 Thin Film. Scientific reports 2019, 9 (1), 1-6.
6. Zhou, R.; Wang, H.; Chang, J.; Yu, C.; Dai, H.; Chen, Q.; Zhou, J.; Yu, H.; Sun, G.; Huang, W., Ammonium Intercalation Induced Expanded 1T-Rich Molybdenum Diselenides for Improved Lithium Ion Storage. ACS Applied Materials & Interfaces 2021, 13 (15), 17459-17466.
7. Zhang, J.; Yang, A.; Wu, X.; van de Groep, J.; Tang, P.; Li, S.; Liu, B.; Shi, F.; Wan, J.; Li, Q., Reversible and selective ion intercalation through the top surface of few-layer MoS 2. Nature communications 2018, 9 (1), 1-9.
8. Yajima, T.; Koshiko, M.; Zhang, Y.; Oguchi, T.; Yu, W.; Kato, D.; Kobayashi, Y.; Orikasa, Y.; Yamamoto, T.; Uchimoto, Y., Selective and low temperature transition metal intercalation in layered tellurides. Nature communications 2016, 7 (1), 1-8.
9. Ranganathan, K.; Fiegenbaum‐Raz, M.; Ismach, A., Large‐Scale and Robust Multifunctional Vertically Aligned MoS2 Photo‐Memristors. Advanced Functional Materials 2020, 30 (51), 2005718.
10. Zahoor, F.; Zulkifli, T. Z. A.; Khanday, F. A., Resistive random access memory (RRAM): an overview of materials, switching mechanism, performance, multilevel cell (MLC) storage, modeling, and applications. Nanoscale research letters 2020, 15 (1), 1-26.
11. Feng, P.; Chao, C.; Wang, Z.-s.; Yang, Y.-c.; Jing, Y.; Fei, Z., Nonvolatile resistive switching memories-characteristics, mechanisms and challenges. Progress in Natural Science: Materials International 2010, 20, 1-15.
12. Yang, J. J.; Inoue, I. H.; Mikolajick, T.; Hwang, C. S., Metal oxide memories based on thermochemical and valence change mechanisms. MRS bulletin 2012, 37 (2), 131-137.
13. Banerjee, W., Challenges and applications of emerging nonvolatile memory devices. Electronics 2020, 9 (6), 1029.
14. Jameson, J. R.; Blanchard, P.; Dinh, J.; Gonzales, N.; Gopalakrishnan, V.; Guichet, B.; Hollmer, S.; Hsu, S.; Intrater, G.; Kamalanathan, D., Conductive bridging RAM (CBRAM): then, now, and tomorrow. ECS Transactions 2016, 75 (5), 41.
15. Valov, I.; Tsuruoka, T., Effects of moisture and redox reactions in VCM and ECM resistive switching memories. Journal of Physics D: Applied Physics 2018, 51 (41), 413001.
16. Zhu, L.; Zhou, J.; Guo, Z.; Sun, Z., An overview of materials issues in resistive random access memory. Journal of Materiomics 2015, 1 (4), 285-295.
17. Wang, W.; Laudato, M.; Ambrosi, E.; Bricalli, A.; Covi, E.; Lin, Y.-H.; Ielmini, D., Volatile resistive switching memory based on Ag ion drift/diffusion—Part II: Compact modeling. IEEE Transactions on Electron Devices 2019, 66 (9), 3802-3808.
18. Ambrosi, E.; Bricalli, A.; Laudato, M.; Ielmini, D., Impact of oxide and electrode materials on the switching characteristics of oxide ReRAM devices. Faraday discussions 2019, 213, 87-98.
19. Bai, Y.; Wu, H.; Zhang, Y.; Wu, M.; Zhang, J.; Deng, N.; Qian, H.; Yu, Z., Low power W: AlOx/WOx bilayer resistive switching structure based on conductive filament formation and rupture mechanism. Applied Physics Letters 2013, 102 (17), 173503.
20. Woo, J.; Moon, K.; Song, J.; Lee, S.; Kwak, M.; Park, J.; Hwang, H., Improved synaptic behavior under identical pulses using AlO x/HfO 2 bilayer RRAM array for neuromorphic systems. IEEE Electron Device Letters 2016, 37 (8), 994-997.
21. Banerjee, W.; Xu, X.; Lv, H.; Liu, Q.; Long, S.; Liu, M., Variability improvement of tio x/al2o3 bilayer nonvolatile resistive switching devices by interfacial band engineering with an ultrathin al2o3 dielectric material. ACS omega 2017, 2 (10), 6888-6895.
22. Hsu, C.-W.; Wang, Y.-F.; Wan, C.-C.; Wang, I.-T.; Chou, C.-T.; Lai, W.-L.; Lee, Y.-J.; Hou, T.-H., Homogeneous barrier modulation of TaOx/TiO2 bilayers for ultra-high endurance three-dimensional storage-class memory. Nanotechnology 2014, 25 (16), 165202.
23. Niu, G.; Calka, P.; der Maur, M. A.; Santoni, F.; Guha, S.; Fraschke, M.; Hamoumou, P.; Gautier, B.; Perez, E.; Walczyk, C., Geometric conductive filament confinement by nanotips for resistive switching of HfO 2-RRAM devices with high performance. Scientific reports 2016, 6 (1), 1-9.
24. Krishnamurthi, S.; Brocks, G., 1D metallic states at 2D transition metal dichalcogenide semiconductor heterojunctions. npj 2D Materials and Applications 2021, 5 (1), 1-6.
25. Dong, R.; Kuljanishvili, I., Progress in fabrication of transition metal dichalcogenides heterostructure systems. Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena 2017, 35 (3), 030803.
26. Raza, A.; Qumar, U.; Hassan, J.; Ikram, M.; Ul-Hamid, A.; Haider, J.; Imran, M.; Ali, S., A comparative study of dirac 2D materials, TMDCs and 2D insulators with regard to their structures and photocatalytic/sonophotocatalytic behavior. Applied Nanoscience 2020, 10 (10), 3875-3899.
27. Shi, Y.; Zhang, H.; Chang, W.-H.; Shin, H. S.; Li, L.-J., Synthesis and structure of two-dimensional transition-metal dichalcogenides. MRS Bulletin 2015, 40 (7), 566-576.
28. Hoang Huy, V. P.; Ahn, Y. N.; Hur, J., Recent Advances in Transition Metal Dichalcogenide Cathode Materials for Aqueous Rechargeable Multivalent Metal-Ion Batteries. Nanomaterials 2021, 11 (6), 1517.
29. Brent, J. R.; Savjani, N.; O'Brien, P., Synthetic approaches to two-dimensional transition metal dichalcogenide nanosheets. Progress in Materials Science 2017, 89, 411-478.
30. Wong, S. L.; Liu, H.; Chi, D., Recent progress in chemical vapor deposition growth of two-dimensional transition metal dichalcogenides. Progress in Crystal Growth and Characterization of Materials 2016, 62 (3), 9-28.
31. Zhang, X.; Teng, S. Y.; Loy, A. C. M.; How, B. S.; Leong, W. D.; Tao, X., Transition metal dichalcogenides for the application of pollution reduction: A review. Nanomaterials 2020, 10 (6), 1012.
32. Hamedani, Y.; Macha, P.; Bunning, T. J.; Naik, R. R.; Vasudev, M. C., Plasma-enhanced chemical vapor deposition: Where we are and the outlook for the future. InTech: 2016.
33. Lin, W.-S.; Medina, H.; Su, T.-Y.; Lee, S.-H.; Chen, C.-W.; Chen, Y.-Z.; Manikandan, A.; Shih, Y.-C.; Yang, J.-H.; Chen, J.-H., Selection role of metal oxides into transition metal dichalcogenide monolayers by a direct selenization process. ACS applied materials & interfaces 2018, 10 (11), 9645-9652.
34. Jung, Y.; Zhou, Y.; Cha, J. J., Intercalation in two-dimensional transition metal chalcogenides. Inorganic Chemistry Frontiers 2016, 3 (4), 452-463.
35. Liu, X.-C.; Zhao, S.; Sun, X.; Deng, L.; Zou, X.; Hu, Y.; Wang, Y.-X.; Chu, C.-W.; Li, J.; Wu, J., Spontaneous self-intercalation of copper atoms into transition metal dichalcogenides. Science advances 2020, 6 (7), eaay4092.
36. Hong, G.; Li, N.; Yang, H.; Chen, H.-s.; Song, W.; Fang, D., Changes of adhesion properties for negative electrode and positive electrode under wet conditions and different states of charge. International Journal of Adhesion and Adhesives 2021, 108, 102870.
37. Guarnieri, V.; Biazi, L.; Marchiori, R.; Lago, A., Platinum metallization for MEMS application: Focus on coating adhesion for biomedical applications. Biomatter 2014, 4 (1), e28822.
38. Lu, X.; Utama, M. I. B.; Lin, J.; Gong, X.; Zhang, J.; Zhao, Y.; Pantelides, S. T.; Wang, J.; Dong, Z.; Liu, Z., Large-area synthesis of monolayer and few-layer MoSe2 films on SiO2 substrates. Nano letters 2014, 14 (5), 2419-2425.
39. Schulmeyer, W. V.; Ortner, H. M., Mechanisms of the hydrogen reduction of molybdenum oxides. International Journal of Refractory Metals and Hard Materials 2002, 20 (4), 261-269.
40. Laserna, J., An introduction to Raman spectroscopy: introduction and basic principles. Raman/Infrared Spectroscopy 2014.
41. Van der Heide, P., X-ray photoelectron spectroscopy: an introduction to principles and practices. John Wiley & Sons: 2011.
42. Russ, J. C., Fundamentals of energy dispersive X-ray analysis: Butterworths monographs in materials. Butterworth-Heinemann: 2013.
43. Ribeiro, J.; DaBoit, K.; Flores, D.; Kronbauer, M. A.; Silva, L. F., Extensive FE-SEM/EDS, HR-TEM/EDS and ToF-SIMS studies of micron-to nano-particles in anthracite fly ash. Science of the total environment 2013, 452, 98-107.
44. Gupta, U.; Naidu, B.; Maitra, U.; Singh, A.; Shirodkar, S. N.; Waghmare, U. V.; Rao, C., Characterization of few-layer 1T-MoSe2 and its superior performance in the visible-light induced hydrogen evolution reaction. APL Materials 2014, 2 (9), 092802.
45. Jiang, M.; Zhang, J.; Wu, M.; Jian, W.; Xue, H.; Ng, T.-W.; Lee, C.-S.; Xu, J., Synthesis of 1T-MoSe 2 ultrathin nanosheets with an expanded interlayer spacing of 1.17 nm for efficient hydrogen evolution reaction. Journal of Materials Chemistry A 2016, 4 (39), 14949-14953.
46. Qu, Y.; Medina, H.; Wang, S. W.; Wang, Y. C.; Chen, C. W.; Su, T. Y.; Manikandan, A.; Wang, K.; Shih, Y. C.; Chang, J. W., Wafer Scale Phase‐Engineered 1T‐and 2H‐MoSe2/Mo Core–Shell 3D‐Hierarchical Nanostructures toward Efficient Electrocatalytic Hydrogen Evolution Reaction. Advanced Materials 2016, 28 (44), 9831-9838.
47. Xue, F.; Chen, Y.-T.; Wang, Y.; Zhou, F.; Chang, Y.-F.; Fowler, B.; Lee, J., The effect of plasma treatment on reducing electroforming voltage of silicon oxide RRAM. ECS Transactions 2012, 45 (6), 245.
48. Shi, J.; Li, Z.; Zhang, D.; Liu, Q.; Sun, Z.; Huang, S., Fabrication of Cu (In, Ga) Se2 thin films by sputtering from a single quaternary chalcogenide target. Progress in Photovoltaics: Research and Applications 2011, 19 (2), 160-164.
49. Takahashi, T.; Yamamoto, O.; Matsuyama, F.; Noda, Y., Ionic conductivity and coulometric titration of copper selenide. Journal of Solid State Chemistry 1976, 16 (1-2), 35-39.
50. Park, J.; Jo, M.; Bourim, E. M.; Yoon, J.; Seong, D.-J.; Lee, J.; Lee, W.; Hwang, H., Investigation of state stability of low-resistance state in resistive memory. IEEE Electron Device Letters 2010, 31 (5), 485-487.
51. Wang, W.; Wang, M.; Ambrosi, E.; Bricalli, A.; Laudato, M.; Sun, Z.; Chen, X.; Ielmini, D., Surface diffusion-limited lifetime of silver and copper nanofilaments in resistive switching devices. Nature communications 2019, 10 (1), 1-9.
52. Hsu, L.-Y.; Wu, N.; Rabitz, H., Conductance and activation energy for electron transport in series and parallel intramolecular circuits. Physical Chemistry Chemical Physics 2016, 18 (47), 32087-32095.
53. Borgschulte, A.; Sambalova, O.; Delmelle, R.; Jenatsch, S.; Hany, R.; Nüesch, F., Hydrogen reduction of molybdenum oxide at room temperature. Scientific reports 2017, 7 (1), 1-9.
54. Ielmini, D., Brain-inspired computing with resistive switching memory (RRAM): Devices, synapses and neural networks. Microelectronic Engineering 2018, 190, 44-53.
55. Chen, P.-Y.; Lin, B.; Wang, I.-T.; Hou, T.-H.; Ye, J.; Vrudhula, S.; Seo, J.-s.; Cao, Y.; Yu, S. In Mitigating effects of non-ideal synaptic device characteristics for on-chip learning, 2015 IEEE/ACM International Conference on Computer-Aided Design (ICCAD), IEEE: 2015; pp 194-199.