Aug 16, 2011
Flexible memory: ultrathin graphite sheets sandwiched between PMMA
Bistable organic memory (BOM) cells have emerged as excellent candidates for next generation devices, and designs consisting of ultrathin graphite sheets (UGS) offer advantages of low cost and simple fabrication, even for large-area specifications. To study how the devices respond to bending, scientists in Korea have fabricated BOM test structures based on a multilayered PMMA/UGS/PMMA polymer composite.
High-resolution transmission electron microscopy (HRTEM) and TEM measurements were performed to investigate the microstructural properties of the PMMA/UGS/PMMA films. Current–voltage (I–V) measurements on the Al/PMMA/UGS/PMMA/indium tin oxide (ITO)/poly(ethylene terephthalate) (PET) devices at 300 K showed a current bistability due to the existence of the UGS, indicative of charge storage in the UGS.
Before and after bending
Using current–voltage (I–V), current–time (I–t) and current–cycle data, the BOM device was characterized before and after bending to examine the electrical performance and memory stability of the unit. The test rig includes bending tools with three different radii of surface curvature.
The I–V results reveal electrical bistable behaviour before and after bending. It is worth noting that the flexible organic memory device showed very similar performance to graphene-embedded BOM, when referring to values such as the maximum Ion/Ioff ratio of the I–V curves of 5 × 106, a retention stability of 4.8 × 104 s and endurance to electrical stress above 1 × 105 cycles.
The memory characteristics of the BOM devices compared well before and after bending and were stable during repetitive mechanical bending. These results indicate that flexible BOM devices based on UGS and PMMA polymer composites hold promise for potential applications in next generation transparent flexible nonvolatile memory devices.
Additional information including full test results can be found in the journal Nanotechnology.
About the author
Dong-Ick Son is a postdoc researcher in the Future Convergence Research Division at Korea Institute of Science and Technology (KIST). Jae Ho Shim is a graduate student in the Division of Electronics and Computer Engineering at Hanyang University. Dong-Hee Park is a research scientist in the Future Convergence Research Division at KIST. Jae-Hun Jung is a PhD student in the Division of Electronics and Computer Engineering at Hanyang University. Jung-Min Lee is a graduate student in the Department of Materials Science and Engineering at Hanyang University. Won-Il Park is a professor in the Department of Materials Science and Engineering at Hanyang University. Tae-Whan Kim is a professor in the Division of Electronics and Computer Engineering at Hanyang University. Won-Kook Choi, who is a team leader, is a principal research scientist in the Future Convergence Research Division at KIST. This work was support by the KIST Future Resource Program (Contract 2E22111).