Tae Whan Kim

Bio: Tae Whan Kim is an academic researcher. The author has contributed to research in topics: Write once read many. The author has an hindex of 1, co-authored 1 publications receiving 27 citations.

Memory effects and carrier transport mechanisms of write-once- read-many-times memory devices fabricated using poly(3-hexylthiophene) molecules embedded in a polymethylmethacrylate layer on a flexible substrate

Abstract: The memory effects and the carrier transport mechanisms of write-once-read-many-times (WORM) memory devices fabricated using poly(3-hexylthiophene) (P3HT) molecules embedded in a polymethylmethacrylate (PMMA) polymer layer on a flexible substrate were investigated. Current-voltage (I-V) curves at 300 K for Al/P3HT:PMMA/indium-tin-oxide WORM device showed a permanent memory behavior with an ON/OFF ratio of 104. The estimated retention time of the ON state of the WORM device was more than 10 years. The carrier transport mechanisms of the WORM memory devices are described using several models to fit the experimental I-V data.

Towards the development of flexible non-volatile memories.

Abstract: Flexible non-volatile memories have attracted tremendous attentions for data storage for future electronics application. From device perspective, the advantages of flexible memory devices include thin, lightweight, printable, foldable and stretchable. The flash memories, resistive random access memories (RRAM) and ferroelectric random access memory/ferroelectric field-effect transistor memories (FeRAM/FeFET) are considered as promising candidates for next generation non-volatile memory device. Here, we review the general background knowledge on device structure, working principle, materials, challenges and recent progress with the emphasis on the flexibility of above three categories of non-volatile memories.

Stretchable organic memory: toward learnable and digitized stretchable electronic applications

Abstract: A stretchable organic digital information storage device has been developed, which potentially advances the development of future smart and digital stretchable electronic systems. The stretchable organic memory with a buckled structure was configured by a mechanically flexible and elastic graphene bottom electrode and polymer compound. The current–voltage curve of the wrinkled memory device demonstrated electrical bistability with typical write-once-read-many times memory features and a high ON/OFF current ratio (∼105). Even under repetitive stretching, the stretchable organic memory exhibited excellent electrical switching functions and memory effects. We believe the first proof-of-concept presentation of the stretchable organic nonvolatile memory may accelerate the development of information storage device in various stretchable electronic applications, such as stretchable display, wearable computer and artificial skin. Stretchable and foldable electronic devices are very attractive, not only for their practicality but also for their potential in as-yet-undeveloped applications, such as artificial electronic skin. Now, Yang-Fang Chen from the National Taiwan University and co-workers have constructed a stretchable organic memory device. Although a variety of flexible organic electronic devices have already been built, which include transistors or solar cells, building stretchable memory devices has remained a challenge. This is because they typically contain a brittle metal electrode, and their fabrication also involves processes — such as spin coating — that are incompatible with flexible substrates. The researchers circumvented these issues by buckling both a graphene, rather than metallic, electrode and the active memory layers over a pre-stretched poly(dimethylsiloxane) elastomer. When the pre-strain was released, the materials adopted a wrinkled structure that endowed them with flexibility. The resulting device showed good electrical switching behavior and memory effects after several stretch/release cycles. A stretchable wrinkled organic memory has been successfully demonstrated. The stretchable organic memory with a graphene bottom electrode possesses rippled structures. The stretchable organic memory exhibits excellent electrical switching behaviors and memory effects even under repetitive stretching. It is believed that this stretchable organic memory may be beneficial for digital information storage in future stretchable electronic systems.

Tunable electrical memory characteristics by the morphology of self-assembled block copolymers:PCBM nanocomposite films

Abstract: Resistive switchable memory devices were fabricated using self-assembled composite thin films of asymmetric poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) block copolymers (BCP) and fullerene derivatives (PCBM). L1 (with a longer PS block) was comprised of discrete vertical P4VP nanocylinders embedded within the PS matrix whereas L2 (with a longer P4VP block) revealed a reverse morphology with a horizontal orientation. They were used to control the spatial location or distribution of the PCBM and the resultant memory characteristics. The devices with ITO/BCP:PCBM/Al configurations exhibited variable multi-electronic characteristics, changing from insulating to bistable memory switching and highly conducting, as the PCBM content increased. The L1:PCBM memory device showed non-volatile write-once-read-many-times (WORM) memory behavior but the L2:PCBM device exhibited a volatile nature of static random access memory (SRAM). Both L1 and L2:PCBM composite devices revealed the improved switching performance upon solvent annealing procedures of the composite thin film. Our results suggested that the controlled morphology of the BCP/PCBM composite could create nanoscale charge-storage elements for a high density memory device with a reduced bit cell size.

Ultra-flexible nonvolatile memory based on donor-acceptor diketopyrrolopyrrole polymer blends

Abstract: Flexible memory cell array based on high mobility donor-acceptor diketopyrrolopyrrole polymer has been demonstrated. The memory cell exhibits low read voltage, high cell-to-cell uniformity and good mechanical flexibility, and has reliable retention and endurance memory performance. The electrical properties of the memory devices are systematically investigated and modeled. Our results suggest that the polymer blends provide an important step towards high-density flexible nonvolatile memory devices.

Tunable Electrical Memory Characteristics Using Polyimide:Polycyclic Aromatic Compound Blends on Flexible Substrates

Abstract: Resistance switching memory devices with the configuration of poly(ethylene naphthalate)(PEN)/Al/polyimide (PI) blend/Al are reported. The active layers of the PI blend films were prepared from different compositions of poly[4,4′-diamino-4″-methyltriphenylamine-hexafluoroisopropylidenediphthalimide] (PI(AMTPA)) and polycyclic aromatic compounds (coronene or N,N-bis[4-(2-octyldodecyloxy)phenyl]-3,4,9,10-perylenetetracarboxylic diimide (PDI-DO)). The additives of large π-conjugated polycyclic compounds can stabilize the charge transfer complex induced by the applied electric field. Thus, the memory device characteristic changes from the volatile to nonvolatile behavior of flash and write-once-read-many times (WORM) as the additive contents increase in both blend systems. The main differences between these two blend systems are the threshold voltage values and the additive content to change the memory behavior. Due to the stronger accepting ability and higher electron affinity of PDI-DO than those of coronen...