Due to increasing interest in consumer electronics, there is great demand for high-density, high-speed, long retention time (non-volatile) and low power consumption memory devices. Organic Field-Effect Transistor (OFET) memory devices have been considered to be promising candidates for next-generation non-volatile memory devices due to their non-destructive read-out properties, single transistor realization, and excellent compatibility with integrated circuits. The device shown in Fig. 1a incorporates an additional charge-trapping layer, such as metallic nanoparticles, a planar metallic sheet or polymer electrets, between the semiconductor layer and the gate dielectric layer. Fig. 1b shows the operation principle of p-type OFET memory. The p-type OFET memory is operated by applying a negative gate bias between the gate and the source electrode, where holes from the semiconductor channel tunnel through a potential barrier into the charge storage layer. The trapped charges affect the distribution of carriers in the semiconducting channel, thus resulting in shifts of threshold voltage (VTH), corresponding to the programming (PGM) or erasing operation (ERS). As a result, the digital “0” and “1” signals in one bit are determined by the erasing and programming operations, corresponding to low and high drain currents, respectively. Precise control of the amount of charge stored in the specific floating-gate could potentially solve the fundamental scaling-down issues and meet the requirements for high-density memory devices. Recently, Prof. Wen-Chang Chen, Dr. Chien-Chung Shih, and Dr. Yu-Cheng Chiu of National Taiwan University, Prof. Wen-Ya Lee of National Taipei University of Technology, Prof. Cheng-Liang Liu of National Central University, and Dr. Redouane Borsali of CNRS, France, employed nanostructured floating gates or renewable oligosaccharide dielectrics as charge storage layers to achieve high-performance non-volatile organic transistor-type memory, as described in the following (Fig. 2). (1) The concept of double floating-gates, bipolar charge trapping, and discrete trapping sites is first combined to develop high-performance non-volatile OFET memory. The studied double floating-gate memory could simultaneously store holes and electrons on copper phthalocyanine (CuPc) nanoparticles and needle C60 single crystals, respectively, leading to a broad memory window (~4.4 V), low power consumption (±5 V), long data retention time (~104 s), and good writing/erasing endurance (over 100 cycles). (2) A molecular nano-floating gate (NFG) consisting of pentacene-based transistor memory devices is developed using conjugated polymer nanoparticles (CPN), such as polyfluorene (PF), as the discrete trapping sites embedded in an insulating polymer, poly(methacrylic acid) (PMAA). By inserting PF nanoparticles as the floating gate, the transistor memory device reveals a controllable threshold voltage shift, indicating effective electron-trapping by the PF CPN. (3) Renewable oligosaccharides are employed as the charge storage layer in the OFET memory device because the charged hydroxyl groups facilitate the formation of strong hydrogen bonding to stabilize trapped charges and remain stable in a high-conducting state, even after successive stresses of reverse gate biases. This is the first example of employing renewable sugar-based materials as a charge storage layer that exhibit a WORM (write-once-read-many-times) memory characteristic with an ON/OFF current ratio larger than 106. The above results can meet the requirements for next-generation organic non-volatile transistor-type memory devices. References: 1. 1. H. C Chang, C. Lu, C. L. Liu, and W. C. Chen, “Single Crystal C60 Needle/CuPc Nanoparticle Double Floating-Gate for Low-Voltage Organic Transistor Based Nonvolatile Memory Devices”, Adv. Mater., 27: 27-33 (2015). 2. C. C. Shih, Y. C. Chiu, W. Y. Lee, J. Y. Chen and W. C. Chen, “Conjugated Polymer Nanoparticles as Nano Floating Gate Electrets for High Performance Non-volatile Organic Transistor Memory Devices“, Adv. Funct. Mater., 25: 1511-1519 (2015). 3. Y. C. Chiu, H. S. Sun, W. Y. Lee, S. Halila, R. Borsali, and W. C. Chen, “Oligosaccharide Carbohydrate Dielectrics toward High Performance Non-Volatile Transistor Memory Devices”, Adv. Mater., 27: 6257-6264 (2015). Professor Wen-Chang Chen Department of Chemical Engineering National Taiwan University chenwc@ntu.edu.tw References 1. Hsuan-Chun Chang, Chien Lu, Cheng-Liang Liu, Wen-Chang Chen. (2015). Single Crystal C60 Needle/CuPc Nanoparticle Double Floating-Gate for Low- Voltage Organic Transistor Based Nonvolatile Memory Devices. Advanced Materials, 27(1), 27-33. DOI: 10.1002/adma.201403771 2. Chien-Chung Shih, Yu-Cheng Chiu, Wen-Ya Lee, Jung- Yao Chen, and Wen-Chang Chen. (2015). Conjugated Polymer Nanoparticles as Nano Floating Gate Electrets for High Performance Non-volatile Organic Transistor Memory Devices. Advanced Functional Materials, 25(10), 1511-1519. DOI: 10.1002/ adfm.201404329 3. Yu-Cheng Chiu, Han-Sheng Sun, Wen-Ya Lee, Sami Halila, Redouane Borsali, Wen-Chang Chen. (2015). Oligosaccharide Carbohydrate Dielectrics toward High Performance Non- Volatile Transistor Memory Devices. Advanced Materials, 27, 6257-6264. DOI: 10.1002/ adma.201502088 Professor Wen-Chang Chen Department of Chemical Engineering chenwc@ntu.edu.tw