Electrical bistability,negative differential resistance and carrier transport in flexible organic memory device based on polymer bilayer structure |
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| Affiliation: | 1. School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031, China;2. Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, Superconductivity and New Energy R&D Center (SNERDC), Southwest Jiaotong University, Chengdu, Sichuan 610031, China;3. College of Lab Medicine, Hebei North University, Zhangjiakou 075000, China;4. College of Physical Science and Technology, Sichuan University, Chengdu 610064, China;5. Institute for Clean Energy & Advanced Materials (ICEAM), Southwest University, Chongqing 400715, China;1. Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology, Douliu, 64002, Taiwan, ROC;2. Department of Electronic Engineering, National Yunlin University of Science and Technology, Douliu, 64002, Taiwan, ROC;3. Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Douliu, 64002, Taiwan, ROC;1. PPGFis, Instituto de Física, UFRGS, Porto Alegre, RS 91501-970, Brazil;2. Lapol, Escola de Engenharia, UFRGS, Porto Alegre, RS 91501-970, Brazil;1. Department of Mechanical and Mechatronics Engineering, Waterloo Institute for Nanotechnology, Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada;2. School of Physical Science and Technology, Key Laboratory of Advanced Technology of Materials (Ministry of Education of China), Southwest Jiaotong University, Chengdu, Sichuan, 610031, China;3. School of Artificial Intelligence, Southwest University, Chongqing, 400715, China;4. Institute for Clean Energy & Advanced Materials (ICEAM), Southwest University, Chongqing, 400715, China |
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| Abstract: | Bistable nonvolatile memory devices containing two different layers of polymers, viz. MEH-PPV (poly2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenyl vinylene]) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)) has been fabricated by a simple spin-coating technique on flexible polyimide (PI) substrates with a structure Al/MEH-PPV/PEDOT:PSS/Ag-Pd/PI. The current–voltage measurements of the as-fabricated devices showed a nonvolatile electrical bistability with electric field induced charge transfer through the polymer layers and negative differential resistance (NDR) which is attributed to the charge trapping in the MEH-PPV layer. The current ON/OFF ratio between the high-conducting state (ON state) and low-conducting state (OFF state) is found to be of the order of 103 at room temperature which is comparable to organic field effect transistor based memory devices. We propose that such an improvement of rectification ratio (ON/OFF ratio) is caused due to the inclusion of PEDOT:PSS, which serves as a conducting current path for carrier transport; however, NDR is an effect of the trapped charges in the MEH-PPV electron confinement layer. The device shows excellent stability over 104 s without any significant degradation under continuous readout testing in both the ON and OFF states. The carrier transport mechanism of the fabricated organic bistable device has been explained on the basis of different conduction mechanisms such as thermionic emission, space-charge-limited conduction, and Fowler–Nordheim tunneling. A band diagram is proposed to explain the charge transport phenomena. These bilayer structures are free from the drawbacks of the single organic layer based memory devices where the phase separation between the nanoparticles and polymers leads to the degradation of device stability and lifetime. |
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| Keywords: | Memory device Electrical bistability Negative differential resistance Conduction mechanism |
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