本研究以射頻磁控濺鍍法製備Sm2Ti2O7薄膜於ITO基板上，探討不同濺鍍時間、上電極、濺鍍氣氛、退火溫度和金屬後退火處理對材料成分、微觀結構及電阻轉換特性的影響。所有條件下的元件都呈現負開正關的雙極電阻轉換特性。其導通機制是由氧空缺所形成的導電燈絲來主導，氧空缺的含量可以藉由不同濺鍍氣氛、退火溫度來調控。第一部分為探討不同濺鍍時間(5分、15分、25分)對電阻式記憶體的特性影響，濺鍍5分鐘的薄膜具有最多操作次數達到1300次。因為薄膜厚度較薄較容易形成導電燈絲，因此操作次數較多。第二部分為探討不同上電極對電阻式記憶體的影響，與Al作為上電極的元件相比，以Ti作為上電極的元件操作次數較少，操作電壓較大。這是因為上下電極功函數會對元件造成顯著影響。第三部分為探討不同濺鍍氣氛氧氬比對電阻式記憶體的影響。氧濃度增加會降低粒子到達基板的能量，導致生長速率降低使膜厚下降。氧濃度增加會填補薄膜中的空缺，因此當氧含量從0%增加到30%，氧空缺從61.2%顯著降低到32.14%。有通氧的操作次數和未通氧相比有下降是因為氧空缺含量減少所導致。第四部分為探討退火對電阻式記憶體的影響，退火後的薄膜是不需要electroforming的。第五部分為探討金屬後退火對電阻式記憶體的影響，經過金屬後退火的元件會生成AlOx界面層，可以有效防止氧離子向外逸出，因此可以提升電阻轉換的特性。在本研究中經過350°C 金屬後退火的元件具有最優化的電阻轉換特性，其操作次數可達8099次，高低阻態比值>10，在室溫和85°C 下的保留時間皆可達104秒，因此Sm2Ti2O7薄膜很有潛力應用於電阻式記憶體。

The resistive switching (RS) properties of amorphous Sm2Ti2O7 thin films prepared by using RF sputtering were investigated and the effect of different sputtering time, sputtering atmosphere, top electrode, annealing temperature, post-metallization annealing (PMA) on the RS properties were analyzed. Comparison of as-deposited Sm2Ti2O7 thin film device and the device after PMA treatment, the latter exhibits better RS properties, including more uniform set voltages and reset voltages, more switching cycle times and higher Ron/Roff ratio. The prepared samples all revealed bipolar resistive switching (BRS) behavior. The results indicated that the conductive mechanism in terms of the concentration of oxygen vacancies can be controlled by different deposition atmosphere (Ar/O2) ratio, different annealing temperature and film thickness. Additionally, the resistive switching properties can be enhanced by PMA treatment due to the formation of AlOx interface layer, which prevents the oxygen ions from out-diffusion through the boundaries. At the PMA temperature of 350oC, the two resistance states can be distinguished in a range of >10 over 8099 switching cycles along with a retention of 104 s at room temperature and 85ºC, showing promise for non-volatile memory applications.

[1] W. Banerjee,Challenges and Applications of Emerging Nonvolatile Memory Devices, Electronics, vol. 9, no. 6, Jun 2020, Art no. 1029.
[2] S. Munjal and N. Khare, Advances in resistive switching based memory devices, Journal of Physics D-Applied Physics, vol. 52, no. 43, Oct 2019, Art no. 433002.
[3]L.P. Fu, Y.T. Li, G.L. Han, X.P. Gao, C.B. Chen, P. Yuan, Stable resistive switching characteristics of ZrO2-based memory device with low-cost, Microelectron. Eng. 172 (2017) 26–29.
[4] Z.J. Shen, C. Zhao, Y.F. Qi, W.Y. Xu, Y.N. Liu, I.Z. Mitrovic, L. Yang, C.Z. Zhao, Advances of RRAM Devices: Resistive Switching Mechanisms, Materials and Bionic Synaptic Application, Nanomaterials, 10 (2020)
[5] B.R. Lee, J.H. Park, T.G. Kim, Micro-light-emitting diode with n-GaN/NiO/Au-based resistive-switching electrode for compact driving circuitry, Journal of Alloys and Compounds, 823 (2020) 153762.
[6] Q.W. Shi, J.X. Wang, I. Aziz, P.S. Lee, Stretchable and Wearable Resistive Switching Random-Access Memory, Advanced Intelligent Systems, 2 (2020).
[7]M. Kawai, K. Ito, N. Ichikawa, Y. Shimakawa, Thermally formed conducting filaments in a single-crystalline NiO thin film, Appl. Phys. Lett. 96 (2010).
[8]Y.T. Chu, M.H. Tsai, C.L. Huang, Resistive switching properties and conduction mechanisms of LaSmOx thin film by RF sputtering for RRAM applications, Mater. Sci. Eng. B-Adv. Funct. Solid-State Mater. 271 (2021).
[9]S.X. Ren, L.Z. Tang, Q. Sun, Z.H. Li, H.F. Yang, W. Chen, Resistive switching and magnetism in transparent a-TiOx films deposited by magnetron sputtering, Journal of Alloys and Compounds, 763 (2018) 638-642.
[10]S. Mondal, C.H. Chueh, T.M. Pan, High-performance flexible Ni/Sm2O3/ITO ReRAM device for low-power nonvolatile memory applications, Ieee Electron Device Lett. 34 (2013) 1145–1147.
[11]J.C. Kim, Y.H. Jeong, J.B. Lim, K.P. Hong, S. Nahm, T.H. Ghong, Y.D. Kim, High- capacitance metal-insulator-metal capacitors using amorphous Sm2Ti2O7 thin film, J. Electrochem. Soc. 154 (2007) G220–G223.
[12] J.W.B. Li, B.J. Kennedy, Phase separation in Tb pyrochlores. Studies of Tb2Zr1-xSnxO7, Journal of Solid State Chemistry, 288 (2020).
[13]Y.H. Jeong, J.C. Kim, J.B. Lim, K.P. Hong, S. Nahm, H.J. Sun, T.H. Ghong, Y.D. Kim, H.J. Lee, Electrical properties of the Sm2Ti2O7 thin films for metal-insulator- metal capacitor applications, J. Appl. Phys. 101 (2007).
[14]W.J. Zhang, Z. Ma, L. Du, H. Li, Role of PEG4000 in sol-gel synthesis of Sm2Ti2O7 photocatalyst for enhanced activity, J. Alloy. Compd. 704 (2017) 26–31.
[15]V. Zinchenko, V. Maksimenko, L. Sadkovska, Y.V. Timukhin, Application of Sm2Ti2O7 in technology of mirrors for He-Ne laser, in: 2010 International Conference on Advanced Optoelectronics and Lasers, IEEE, 2010, pp. 233–235.
[16]D. Ielmini, G. Pedretti, Device and Circuit Architectures for In-Memory Computing, Advanced Intelligent Systems, 2 (2020)
[17]T. Eshita, T. Tamura, Y. Arimoto, Ferroelectric random access memory (FRAM) devices, in: Y. Nishi (Ed.) Advances in Non-Volatile Memory and Storage Technology, 2014, pp. 434-454
[18] H. Kohlstedt et al., “Current status and challenges of ferroelectric memory devices,” Microelectron. Eng. 80, 296–304 (2005).
[19]Lin, C. H., Friddle, P. A., Ma, C. H., Daga, A., & Chen, H. (2001). Effects of thickness on the electrical properties of metalorganic chemical vapor deposited Pb(Zr, Ti)O3(25–100 nm) thin films on LaNiO3 buffered Si. Journal of applied physics, 90(3), 1509-1515.
[20] Muller J, Boscke T S, Schroder U, Mueller S, Brauhaus D, Bottger U, Frey L and Mikolajick T 2012 Ferroelectricity in simple binary ZrO2 and HfO2 Nano Lett. 12 4318–23
[21] T. Olsen, U. Schroder, S. Muller, A. Krause, D. Martin, A. Singh, J. Muller, M. Geidel, T. Mikolajick, Co-sputtering yttrium into hafnium oxide thin films to produce ferroelectric properties, Applied Physics Letters, 101 (2012).
[22] S.J. Kim, J. Mohan, S.R. Summerfelt, J. Kim, Ferroelectric Hf0.5Zr0.5O2 Thin Films: A Review of Recent Advances, Jom, 71 (2019) 246-255.
[23] S. Mueller, J. Mueller, A. Singh, S. Riedel, J. Sundqvist, U. Schroeder, T. Mikolajick, Incipient Ferroelectricity in Al-Doped HfO2 Thin Films, Advanced Functional Materials, 22 (2012) 2412-2417.
[24] J. Robertson, K. Xiong, P.W. Peacock, Electronic and atomic structure of Ge2Sb2Te5 phase change memory material, Thin Solid Films, 515 (2007) 7538-7541.
[25] S. Shindo, Y. Shuang, S. Hatayama, Y. Saito, P. Fons, A.V. Kolobov, K. Kobayashi, Y. Sutou, The importance of contacts in Cu2GeTe3 phase change memory devices, Journal of Applied Physics, 128 (2020).
[26] S. Hatayama, Y. Sutou, D. Ando, J. Koike, K. Kobayashi, Electrical transport mechanism of the amorphous phase in Cr2Ge2Te6 phase change material, Journal of Physics D-Applied Physics, 52 (2019).
[27] S. Slesazeck, T. Mikolajick, Nanoscale resistive switching memory devices: a review, Nanotechnology, 30 (2019).
[28]T. Kato, S. Iwata, D. Oshima, Progress on efficient current-induced magnetization switching, Electrical Engineering in Japan, 212 (2020) 3-10.
[29]E. Carlos, R. Branquinho, R. Martins, A. Kiazadeh, E. Fortunato, Recent progress in solution-based metal oxide resistive switching devices, Adv. Mater. 33 (2021).
[30] M. Uenuma, Y. Ishikawa, Y. Uraoka, Joule heating effect in nonpolar and bipolar resistive random access memory, Applied Physics Letters, 107 (2015).
[31] H.C. Zhou, Y.P. Jiang, X.G. Tang, Q.X. Liu, W.H. Li, Z.H. Tang, Excellent Bipolar Resistive Switching Characteristics of Bi4Ti3O12 Thin Films Prepared via Sol-Gel Process, Nanomaterials, 11 (2021).
[32] C.C. Yang, J.Q. Huang, K.Y. Chen, P.H. Chiu, H.T. Vu, Y.K. Su, Effect of Oxygen Concentration Ratio on a Ga2O3-Based Resistive Random Access Memory, Ieee Access, 7 (2019) 175186-175191.
[33] C.C. Hsu, P.X. Long, Y.S. Lin, Enhancement of Resistive Switching Characteristics of Sol-Gel TiOx RRAM Using Ag Conductive Bridges, Ieee Transactions on Electron Devices, 68 (2021) 95-102.
[34] K. Park, J.S. Lee, Reliable resistive switching memory based on oxygen-vacancy-controlled bilayer structures, Rsc Advances, 6 (2016) 21736-21741.
[35] C. Kumari, I. Varun, S.P. Tiwari, A. Dixit, Robust non-volatile bipolar resistive switching in sol-gel derived BiFeO3 thin films, Superlattices and Microstructures, 120 (2018) 67-74.
[36] H. Ryu, H. Jung, K. Lee, S. Kim, Multi-Level Resistive Switching of Pt/HfO2/TaN Memory Device, Metals, 11 (2021).
[37] L.Q. Wang, W.H. Li, X.G. Tang, X.B. Guo, Q.X. Liu, Y.P. Jiang, Z.H. Tang, Bipolar resistive switching characteristics of PbZrO3/LaNiO3 heterostructure thin films prepared by a sol-gel process, Ceramics International, 47 (2021) 5617-5623.
[38] K.Y. Cheong, I.A. Tayeb, F. Zhao, J.M. Abdullah, Review on resistive switching mechanisms of bio-organic thin film for non-volatile memory application, Nanotechnology Reviews, 10 (2021) 680-709.
[39]M. Lanza, H.S.P. Wong, E. Pop, D. Ielmini, D. Strukov, B.C. Regan, L. Larcher, M.A. Villena, J.J. Yang, L. Goux, A. Belmonte, Y.C. Yang, F.M. Puglisi, J.F. Kang, B. Magyari-Kope, E. Yalon, A. Kenyon, M. Buckwell, A. Mehonic, A. Shluger, H.T. Li, T.H. Hou, B. Hudec, D. Akinwande, R.J. Ge, S. Ambrogio, J.B. Roldan, E. Miranda, J. Sune, K.L. Pey, X. Wu, N. Raghavan, E. Wu, W.D. Lu, G. Navarro, W.D. Zhang, H.Q. Wu, R.W. Li, A. Holleitner, U. Wurstbauer, M.C. Lemme, M. Liu, S.B. Long, Q. Liu, H.B. Lv, A. Padovani, P. Pavan, I. Valov, X. Jing, T.T. Han, K.C. Zhu, S.C. Chen, F. Hui, Y.Y. Shi, Recommended methods to study resistive switching devices, Adv. Electron. Mater. 5 (2019).
[40]S.K. Hong, J.E. Kim, S.O. Kim, S.Y. Choi, B.J. Cho, Flexible Resistive Switching Memory Device Based on Graphene Oxide, Ieee Electron Device Letters, 31 (2010) 1005-1007.
[41] Y.C. Chen, H.C. Yu, C.Y. Huang, W.L. Chung, S.L. Wu, Y.K. Su, Nonvolatile Bio-Memristor Fabricated with Egg Albumen Film, Scientific Reports, 5 (2015).
[42] Z.X. Lim, K.Y. Cheong, Effects of drying temperature and ethanol concentration on bipolar switching characteristics of natural Aloe vera-based memory devices, Physical Chemistry Chemical Physics, 17 (2015) 26833-26853.
[43] C. Gu, J.S. Lee, Flexible Hybrid Organic-Inorganic Perovskite Memory, Acs Nano, 10 (2016) 5413-5418.
[44] S.X. Ren, L.Z. Tang, Q. Sun, Z.H. Li, H.F. Yang, W. Chen, Resistive switching and magnetism in transparent a-TiOx films deposited by magnetron sputtering, Journal of Alloys and Compounds, 763 (2018) 638-642.
[45] J. Shang, W.H. Xue, Z.H. Ji, G. Liu, X.H. Niu, X.H. Yi, L. Pan, Q.F. Zhan, X.H. Xu, R.W. Li, Highly flexible resistive switching memory based on amorphous-nanocrystalline hafnium oxide films, Nanoscale, 9 (2017) 7037-7046.
[46] X.H. Li, X.J. Kuang, J.L. Sun, Rare earth elements based oxide ion conductors, Inorganic Chemistry Frontiers, 8 (2021) 1374-1398.
[47] D.K. Maurya, A. Sardarinejad, K. Alameh, Recent Developments in RF Magnetron Sputtered Thin Films for pH Sensing Applications-An Overview, Coatings, 4 (2014) 756-771.
[48] A. Moumen, G.C.W. Kumarage, E. Comini, P-Type Metal Oxide Semiconductor Thin Films: Synthesis and Chemical Sensor Applications, Sensors, 22 (2022).
[49] M.H. Korayem, H.J. Sharahi, A.H. Korayem, Comparison of frequency response of atomic force microscopy cantilevers under tip-sample interaction in air and liquids, Scientia Iranica, 19 (2012) 106-112.
[50]M. Wang, H.B. Lv, Q. Liu, Y.T. Li, Z.G. Xu, S.B. Long, H.W. Xie, K.W. Zhang, X.Y. Liu, H.T. Sun, X.Y. Yang, M. Liu, Investigation of One-Dimensional Thickness Scaling on Cu/HfOx/Pt Resistive Switching Device Performance, Ieee Electron Device Lett. 33 (2012) 1556–1558.
[51] K.J. Lee, L.W. Wang, T.K. Chiang, Y.H. Wang, Effects of Electrodes on the Switching Behavior of Strontium Titanate Nickelate Resistive Random Access Memory, Materials, 8 (2015) 7191-7198.
[52]C. Ramana, M. Vargas, G. Lopez, M. Noor-A-Alam, M. Hernandez, E. Rubio, Effect of oxygen/argon gas ratio on the structure and optical properties of sputter- deposited nanocrystalline HfO2 thin films, Ceram. Int. 41 (2015) 6187–6193.
[53]R.A. Geioushy, O.A. Fouad, M.M. Rashad, D.A. Rayan, A.T. Kandil, Facile synthesis of nanosized samarium titanate (Sm2Ti2O7) powders: structural, composition, thermal stability, optical and magnetic properties, N. J. Chem. 45 (2021) 7799–7807.
[54]W.Y. Chang, Y.T. Ho, T.C. Hsu, F. Chen, M.J. Tsai, T.B. Wu, Influence of crystalline constituent on resistive switching properties of TiO2 memory films, Electrochem. Solid State Lett. 12 (2009) H135–H137.
[55]C.C. Hsu, P.T. Liu, K.J. Gan, D.B. Ruan, Y.C. Chiu, S.M. Sze, Impact of annealing environment on performance of InWZnO conductive bridge random access memory, Vacuum 191 (2021).
[56]H.N. Wu, M.S. Xue, J.F. Ou, F.J. Wang, W. Li, Effect of annealing temperature on surface morphology and work function of ZnO nanorod arrays, J. Alloy. Compd. 565 (2013) 85–89.
[57]T.T. Guo, T.T. Tan, Z.T. Liu, The effect of annealing temperature on resistive switching behaviors of HfOx film, J. Mater. Sci. -Mater. Electron. 26 (2015) 6699–6703.
[58]C. Zhang, D. Li, P.T. Lai, X.D. Huang, Effects of back interface on performance of dual-gate InGaZnO thin-film transistor with an unisolated top gate structure, Ieee Electron Device Lett. 42 (2021) 1176–1179.
[59]U. Chand, K.C. Huang, C.Y. Huang, C.H. Ho, C.H. Lin, T.Y. Tseng, Investigation of thermal stability and reliability of HfO2 based resistive random access memory devices with cross-bar structure, J. Appl. Phys. 117 (2015).
[60]H.T. Tseng, T.H. Hsu, M.H. Tsai, C.Y. Huang, C.L. Huang, Resistive switching characteristics of sol-gel derived La2Zr2O7 thin film for RRAM applications, J. Alloy. Compd. 899 (2022).
[61]C.J. Lee, Y.C. Chang, L.W. Wang, Y.H. Wang, Nonvolatile resistive switching memory utilizing cobalt embedded in gelatin, Materials 11 (2018).
[62]J.J. Huang, T.C. Chang, J.B. Yang, S.C. Chen, P.C. Yang, Y.T. Chen, H.C. Tseng, S.M. Sze, A.K. Chu, M.J. Tsai, Influence of oxygen concentration on resistance switching characteristics of gallium oxide, Ieee Electron Device Lett. 33 (2012) 1387–1389.
[63]K.-J. Lee, Y.-H. Wang, Effect of alkaline earth metal on AZrOx (A= Mg, Sr, Ba) memory application, Gels 8 (2022) 20.
[64]D.J. Liu, Q.Q. Lin, Z.G. Zang, M. Wang, P.H. Wangyang, X.S. Tang, M. Zhou, W. Hu, Flexible All-Inorganic Perovskite CsPbBr3 Nonvolatile Memory Device, Acs Appl. Mater. Interfaces 9 (2017) 6171–6176.
[65]W.J. Li, J.X. Wan, Z.X. Tu, H. Li, H. Wu, C. Liu, Optimizing endurance performance of Ga2O3 random resistive access memories by altering oxygen vacancy content, Ceram. Int. 48 (2022) 3185–3191.