本研究通過射頻磁控濺鍍系統沉積LaYO3薄膜於ITO玻璃基板上，並利用電子束蒸鍍系統沉積金屬上電極，製備出具電阻轉換行為之MIM結構RRAM元件，進行電阻轉換特性的探討。
第一部分討論不同濺鍍時間沉積之相異薄膜厚度對於元件電阻轉換特性的影響。其中，沉積之薄膜厚度與濺鍍時間呈一線性關係。Al/LaYO3/ITO元件顯示出雙穩態雙極電阻轉換行為，濺鍍25分鐘之Al/LaYO3 (41.7 nm)/ITO元件操作次數可達相對最高的416次，高低阻值比(ROn/ROff)大於10，記憶時間也可達到10000秒。
第二部分透過改變元件之金屬上電極，觀察不同上電極對於元件電阻轉換特性的影響。兩元件皆顯示出雙穩態雙極電阻轉換行為，其中，以Al金屬作為上電極之元件擁有較大的上/下電極功函數差異，故其擁有較為優良的電阻轉換特性。加以分析兩元件之導通機制，發現兩者擁有相似的結果，低阻態時為歐姆傳導機制；高阻態時須分為兩區段，低電壓區段為歐姆傳導機制，而高電壓區段則為蕭特基發射傳導機制。透過蕭特基傳導方程式估計蕭特基能障趨勢，以Ti金屬作為上電極之元件能障高度較低，電子更容易從電極往介電層移動，蕭特基發射距離增加，會有較多的氧離子遷移並填補氧空缺，使得導電燈絲的形成較為困難，需要施加更大的偏壓才能使元件進行電阻轉換。
第三部分在沉積LaYO3薄膜時調變通入之氣氛比例，進而研究不同氬氧比例對於元件電阻轉換特性之影響。隨著氧氣通入之比例增加，元件有更足夠的氧離子與氧空缺結合，導電燈絲斷裂較多，使得元件之高阻阻值上升，高低阻值比(ROn/ROff)得以提升，然而，能障高度隨氧氣通入之比例上升而下降，導電燈絲的形成變得困難，需要更高的操作電壓促使其形成，導致循環次數呈現下降的趨勢，無法有效地提升電阻轉換特性。
第四部分將元件進行薄膜退火處理，探討未退火及不同薄膜退火溫度對於薄膜及元件電阻轉換特性之影響。退火溫度提高使得LaYO3薄膜層中的氧空缺含量增加，同時，ITO玻璃基板中的In離子擴散至LaYO3薄膜層的比例亦有所上升， In離子協助氧空缺形成導電燈絲，促使導電燈絲的形成更為容易，故當薄膜退火溫度為400 ℃時能有效地提升元件的循環次數。
最後，將元件進行電極退火處理，進而研究不同退火製程對於薄膜及元件電阻轉換特性之影響。電極退火後之元件會在Al上電極與LaYO3薄膜層之間產生一AlOx儲氧層，抑制氧離子向外逸散，穩定裝置中氧離子的含量，促使導電燈絲的形成及斷裂穩定，進而提升循環次數。電阻相對較高，可以抑制漏電流的產生，雖然需要較高的操作電壓去進行電阻轉換，但是氧化鋁具有較高之崩潰電壓，使得元件可在較高偏壓下進行操作。其中，電極退火400 ℃之RRAM元件操作次數達到1242次，高低阻值比(ROn/ROff)亦可達1000，擁有優良的電阻轉換特性，為一相當有發展潛力之RRAM元件。

LaYO3 thin films are deposited by RF sputtering and the bipolar resistive switching (BRS) properties of Al/LaYO3/ITO RRAM devices are investigated. The influences on the resistive switching (RS) properties under varied sputtering time, top electrodes, deposition atmosphere, annealing temperature and annealing processes are also studied. The conductive filaments are mainly dominated by oxygen vacancies, the concentration of oxygen vacancies can be influenced by the deposition atmosphere and annealing process. In ions from ITO diffusing into LaYO3 layer after annealing process can enhance the formation of filaments. The different Schottky barrier heights under varied top electrodes and deposition atmosphere also have an effect on the formation of filaments. In addition, the formation of AlOx interface layer after post metal annealing (PMA) has a significant influence on the RS performance of the device. The device post metal annealed at 400 ℃ possesses excellent RS performance with a cycle times of 1242 and a Ron/Roff ratio of 1000, which can be viewed as a quite promising RRAM device in non-volatile memory region.

[1] H.-S. P. Wong, H.-Y. Lee, S. Yu, Y.-S. Chen, Y. Wu, P.-S. Chen, B. Lee, F. T. Chen, M.-J. Tsai, "Metal–oxide RRAM," Proceedings of the IEEE, vol. 100, pp. 1951-1970, 2012.
[2] X. Yan, Y. Li, J. Zhao, Y. Li, G. Bai, and S. Zhu, "Roles of grain boundary and oxygen vacancies in Ba0.6Sr0.4TiO3 films for resistive switching device application," Applied Physics Letters, vol. 108, p. 033108, 2016.
[3] M. Baklanov, M. Green, and K. Maex, Dielectric films for advanced microelectronics vol. 12: Wiley Online Library, 2007.
[4] J. Lopes, M. Roeckerath, T. Heeg, E. Rije, J. Schubert, S. Mantl, V. Afanas’ ev, S. Shamuilia, A. Stesmans, Y. Jia, "Amorphous lanthanum lutetium oxide thin films as an alternative high-κ gate dielectric," Applied physics letters, vol. 89, p. 222902, 2006.
[5] F. Zahoor, T. Z. A. Zulkifli, and F. A. Khanday, "Resistive random access memory (RRAM): an overview of materials, switching mechanism, performance, multilevel cell (MLC) storage, modeling, and applications," Nanoscale research letters, vol. 15, pp. 1-26, 2020.
[6] B. Ku, Y. Abbas, A. S. Sokolov, and C. Choi, "Interface engineering of ALD HfO2-based RRAM with Ar plasma treatment for reliable and uniform switching behaviors," Journal of Alloys and Compounds, vol. 735, pp. 1181-1188, 2018.
[7] X. Pan, Y. Shuai, C. Wu, W. Luo, X. Sun, Y. Yuan, S. Zhou, X. Ou, W. Zhang, "Resistive switching behavior in single crystal SrTiO3 annealed by laser," Applied Surface Science, vol. 389, pp. 1104-1107, 2016.
[8] Z. Yan and J.-M. Liu, "Resistance switching memory in perovskite oxides," Annals of Physics, vol. 358, pp. 206-224, 2015.
[9] B. Mu, H.-H. Hsu, C.-C. Kuo, S.-T. Han, and Y. Zhou, "Organic small molecule-based RRAM for data storage and neuromorphic computing," Journal of Materials Chemistry C, vol. 8, pp. 12714-12738, 2020.
[10] H. Ling, M. Yi, M. Nagai, L. Xie, L. Wang, B. Hu, W. Huang, "Controllable Organic Resistive Switching Achieved by One‐Step Integration of Cone‐Shaped Contact," Advanced Materials, vol. 29, p. 1701333, 2017.
[11] H. Zhao, H. Tu, F. Wei, Y. Xiong, X. Zhang, and J. Du, "Characteristics and mechanism of nano‐polycrystalline La2O3 thin‐film resistance switching memory," physica status solidi (RRL)–Rapid Research Letters, vol. 7, pp. 1005-1008, 2013.
[12] C. Pi, Y. Ren, Z. Liu, and W. Chim, "Unipolar memristive switching in yttrium oxide and RESET current reduction using a yttrium interlayer," Electrochemical and Solid State Letters, vol. 15, p. G5, 2011.
[13] K. Yim, Y. Yong, J. Lee, K. Lee, H.-H. Nahm, J. Yoo, C. Lee, C. S. Hwang, S. Han, "Novel high-κ dielectrics for next-generation electronic devices screened by automated ab initio calculations," NPG Asia Materials, vol. 7, pp. e190-e190, 2015.
[14] G.-S. Park, X.-S. Li, D.-C. Kim, R.-J. Jung, M.-J. Lee, and S. Seo, "Observation of electric-field induced Ni filament channels in polycrystalline NiOx film," Applied Physics Letters, vol. 91, p. 222103, 2007.
[15] M. Liu, Z. Abid, W. Wang, X. He, Q. Liu, and W. Guan, "Multilevel resistive switching with ionic and metallic filaments," Applied Physics Letters, vol. 94, p. 233106, 2009.
[16] T.-L. Tsai, H.-Y. Chang, F.-S. Jiang, and T.-Y. Tseng, "Impact of post-oxide deposition annealing on resistive switching in HfO2-based oxide RRAM and conductive-bridge RAM devices," IEEE Electron Device Letters, vol. 36, pp. 1146-1148, 2015.
[17] D. S. Jeong, R. Thomas, R. Katiyar, J. Scott, H. Kohlstedt, A. Petraru, C. S. Hwang, "Emerging memories: resistive switching mechanisms and current status," Reports on progress in physics, vol. 75, p. 076502, 2012.
[18] 李明道, "新式非揮發性記憶體之發展與挑戰," 國家奈米元件實驗室奈米通訊, vol. 21, pp. 9-14, 2014.
[19] M. Gupta and J. Kedia, "A Review on Resistive Random Access Memory," Int. J. Adv. Res. Electron. Commun. Eng, vol. 7, pp. 184-191, 2018.
[20] C.-L. Lin, C.-C. Tang, S.-C. Wu, P.-C. Juan, and T.-K. Kang, "Impact of oxygen composition of ZnO metal-oxide on unipolar resistive switching characteristics of Al/ZnO/Al resistive RAM (RRAM)," Microelectronic Engineering, vol. 136, pp. 15-21, 2015.
[21] S.-Y. Wang, D.-Y. Lee, T.-Y. Tseng, and C.-Y. Lin, "Effects of Ti top electrode thickness on the resistive switching behaviors of rf-sputtered ZrO2 memory films," Applied Physics Letters, vol. 95, p. 112904, 2009.
[22] K.-C. Chuang, K.-Y. Lin, J.-D. Luo, W.-S. Li, Y.-S. Li, C.-Y. Chu, H.-C. Cheng, "Effects of post-metal annealing on the electrical characteristics of HfOx-based resistive switching memory devices," Japanese Journal of Applied Physics, vol. 56, p. 06GF10, 2017.
[23] C.-Y. Liu, Y.-R. Shih, and S.-J. Huang, "Unipolar resistive switching in a transparent ITO/SiOx/ITO sandwich fabricated at room temperature," Solid state communications, vol. 159, pp. 13-17, 2013.
[24] C. Rohde, B. J. Choi, D. S. Jeong, S. Choi, J.-S. Zhao, and C. S. Hwang, "Identification of a determining parameter for resistive switching of TiO2 thin films," Applied Physics Letters, vol. 86, p. 262907, 2005.
[25] H.-Y. Lee, P.-S. Chen, C.-C. Wang, S. Maikap, P.-J. Tzeng, C.-H. Lin, L.-S. Lee, M.-J. Tsai, "Low-power switching of nonvolatile resistive memory using hafnium oxide," Japanese journal of applied physics, vol. 46, p. 2175, 2007.
[26] A. Beck, J. Bednorz, C. Gerber, C. Rossel, and D. Widmer, "Reproducible switching effect in thin oxide films for memory applications," Applied Physics Letters, vol. 77, pp. 139-141, 2000.
[27] Y. Watanabe, J. Bednorz, A. Bietsch, C. Gerber, D. Widmer, A. Beck, S. Wind, "Current-driven insulator–conductor transition and nonvolatile memory in chromium-doped SrTiO3 single crystals," Applied Physics Letters, vol. 78, pp. 3738-3740, 2001.
[28] C. Ye, J. Wu, G. He, J. Zhang, T. Deng, P. He, H. Wang, "Physical mechanism and performance factors of metal oxide based resistive switching memory: a review," Journal of Materials Science & Technology, vol. 32, pp. 1-11, 2016.
[29] R. Waser and M. Aono, "Nanoionics-based resistive switching memories," Nanoscience And Technology: A Collection of Reviews from Nature Journals, pp. 158-165, 2010.
[30] R. Waser, R. Dittmann, G. Staikov, and K. Szot, "Redox‐based resistive switching memories–nanoionic mechanisms, prospects, and challenges," Advanced materials, vol. 21, pp. 2632-2663, 2009.
[31] A. Sawa, "Resistive switching in transition metal oxides," Materials today, vol. 11, pp. 28-36, 2008.
[32] Y. C. Yang, F. Pan, Q. Liu, M. Liu, and F. Zeng, "Fully room-temperature-fabricated nonvolatile resistive memory for ultrafast and high-density memory application," Nano letters, vol. 9, pp. 1636-1643, 2009.
[33] F.-C. Chiu, "A review on conduction mechanisms in dielectric films," Advances in Materials Science and Engineering, vol. 2014, 2014.
[34] T. I. Awan, A. Bashir, and A. Tehseen, Chemistry of Nanomaterials: Fundamentals and Applications: Elsevier, 2020.
[35] E. L. Thomas, "Crystal growth and the search for highly correlated ternary intermetallic antimonides and stannides," 2006.
[36] R. A. Wilson and H. A. Bullen, "Introduction to Scanning Probe Microscopy (SPM): Basic Theory Atomic Force Microscopy (AFM)," Creative Commons Attribution-Noncommercial-Share Alike, vol. 2, 2006.
[37] M. Wang, H. Lv, Q. Liu, Y. Li, Z. Xu, S. Long, H. Xie, K. Zhang, X. Liu, H. Sun, "Investigation of One-Dimensional Thickness Scaling on Cu/HfOx/Pt Resistive Switching Device Performance," IEEE electron device letters, vol. 33, pp. 1556-1558, 2012.
[38] K.-J. Lee, L.-W. Wang, T.-K. Chiang, and Y.-H. Wang, "Effects of electrodes on the switching behavior of strontium titanate nickelate resistive random access memory," Materials, vol. 8, pp. 7191-7198, 2015.
[39] K.-H. Chen, T.-M. Tsai, C.-M. Cheng, S.-J. Huang, K.-C. Chang, S.-P. Liang, T.-F. Young, "Schottky emission distance and barrier height properties of bipolar switching Gd:SiOx RRAM devices under different oxygen concentration environments," Materials, vol. 11, p. 43, 2018.
[40] C. Ramana, M. Vargas, G. Lopez, M. Noor-A-Alam, M. Hernandez, and E. Rubio, "Effect of oxygen/argon gas ratio on the structure and optical properties of sputter-deposited nanocrystalline HfO2 thin films," Ceramics International, vol. 41, pp. 6187-6193, 2015.
[41] J. B. Lee, S. H. Kwak, and H. J. Kim, "Effects of surface roughness of substrates on the c-axis preferred orientation of ZnO films deposited by rf magnetron sputtering. ," Thin Solid Films, vol. 423, pp. 262-266, 2003.
[42] Z. Ji, Q. Mao, and W. Ke, "Effects of oxygen partial pressure on resistive switching characteristics of ZnO thin films by DC reactive magnetron sputtering," Solid State Communications, vol. 150, pp. 1919-1922, 2010.
[43] W. Zhang, J.-Z. Kong, Z.-Y. Cao, A.-D. Li, L.-G. Wang, L. Zhu, X. Li, Y.-Q. Cao, D. Wu, "Bipolar resistive switching characteristics of HfO2/TiO2/HfO2 trilayer-structure RRAM devices on Pt and TiN-coated substrates fabricated by atomic layer deposition," Nanoscale research letters, vol. 12, pp. 1-11, 2017.
[44] M. Zhao, X. Yan, L. Ren, M. Zhao, F. Guo, J. Zhuang, Y. Du, W. Hao, "The role of oxygen vacancies in the high cycling endurance and quantum conductance in BiVO4‐based resistive switching memory," InfoMat, vol. 2, pp. 960-967, 2020.
[45] J.-B. Yang, T.-C. Chang, J.-J. Huang, S.-C. Chen, P.-C. Yang, Y.-T. Chen, H.-C. Tseng, S. M. Sze, A.-K. Chu, M.-J. Tsai, "Resistive switching characteristics of gallium oxide for nonvolatile memory application," Thin Solid Films, vol. 529, pp. 200-204, 2013.
[46] D. E. Gallardo, C. Bertoni, S. Dunn, N. Gaponik, and A. Eychmüller, "Cathodic and Anodic Material Diffusion in Polymer/Semiconductor‐Nanocrystal Composite Devices," Advanced Materials, vol. 19, pp. 3364-3367, 2007.
[47] Y. C. Jung, S. Seong, T. Lee, S. Y. Kim, I.-S. Park, and J. Ahn, "Effects of Hydrogen annealing temperature on the resistive switching characteristics of HfOx thin films," Materials Science in Semiconductor Processing, vol. 88, pp. 207-213, 2018.
[48] K.-K. Chiang, J.-S. Chen, and J.-J. Wu, "Aluminum electrode modulated bipolar resistive switching of Al/fuel-assisted NiOx/ITO memory devices modeled with a dual-oxygen-reservoir structure," ACS applied materials & interfaces, vol. 4, pp. 4237-4245, 2012.
[49] L. Wu, H. Liu, J. Lin, and S. Wang, "Self-Compliance and High Performance Pt/HfOx/Ti RRAM Achieved through Annealing," Nanomaterials, vol. 10, p. 457, 2020.
[50] U. Chand, K.-C. Huang, C.-Y. Huang, C.-H. Ho, C.-H. Lin, and T.-Y. Tseng, "Investigation of thermal stability and reliability of HfO2 based resistive random access memory devices with cross-bar structure," Journal of Applied Physics, vol. 117, p. 184105, 2015.
[51] P.-S. Chen, H.-Y. Lee, Y.-S. Chen, F. Chen, and M.-J. Tsai, "Improved bipolar resistive switching of HfOx/TiN stack with a reactive metal layer and post metal annealing," Japanese Journal of Applied Physics, vol. 49, p. 04DD18, 2010.
[52] L. Chen, Y. Xu, Q.-Q. Sun, H. Liu, J.-J. Gu, S.-J. Ding, D.W. Zhang, "Highly Uniform Bipolar Resistive Switching With Al2O3 Buffer Layer in Robust NbAlO-Based RRAM," IEEE electron device letters, vol. 31, pp. 356-358, 2010.
[53] P. Misra, S. P. Pavunny, and R. S. Katiyar, "On the resistive switching and current conduction mechanisms of amorphous LaGdO3 films grown by pulsed laser deposition," ECS Transactions, vol. 53, p. 229, 2013.
[54] P. Misra, S. P. Pavunny, Y. Sharma, and R. S. Katiyar, "Resistive Switching and Current Conduction Mechanisms in Amorphous LaLuO3 Thin Films Grown by Pulsed Laser Deposition," Integrated Ferroelectrics, vol. 157, pp. 47-56, 2014.
[55] C.-S. Chien, M.-H. Tsai, and C.-L. Huang, "Electrical properties and current conduction mechanisms of LaGdO3 thin film by RF sputtering for RRAM applications," Journal of Asian Ceramic Societies, vol. 8, pp. 948-956, 2020.