Host Professor Tong Leung welcomes Professor Giovanni Fanchini from Western University to the Department of Chemistry for a seminar about nanostructured flash memory devices based on radical polymers and carbon-based nanomaterials. All are welcome.
Abstract
Professor Fanchini will review the use of thin films of organic polyradicals – organic polymers with one unpaired electron per monomer [1] – for memory devices and other applications.
Although memory devices based on radical polymers have been often proposed, their stability was frequently limited to a few writing cycles, despite the excellent quality of the active layer. To date, the most common nonvolatile memory components use data storage technology devices that are writable once and readable multiple times (WORM). Memory components that are writable, readable and erasable multiple times (FLASH) are more attractive, but their costs are still high. [2]
Professor Fanchini will provide design criteria for flash memory devices using a combination of Kelvin-probe force microscopy (KPFM), electrical transport and optical measurements. [3] As a case study, he will present ultrathin devices in which the active layer is formed by a 10-nm homogeneous film of poly-[1,5-diisopropyl-3-(cis-5-norbornene-exo-2,3-dicarboxiimide) 6-oxoverdazyl] (P6OV). [4] He will also show that high performance of these devices must be associated to the presence three tunable charge states in each monomer: positive, neutral and negative.
In the last part of his talk, as a complement of polyradical memory devices, he will present a very similar class of organic flash memory devices, based on “curved” carbon quantum dots containing fivefold and sevenfold aromatic carbon rings, in addition to sixfold rings typically featured by commonly synthesized sp2 carbon-based nanomaterials, including graphene, carbon nanotubes, and flat and luminescent graphene quantum dots. Paramagnetic centers associated to fivefold and sevenfold rings are anticipated to be essential to memory effects and memory device operation from these systems. [5]
Professor Fanchini will demonstrate that careful engineering of the anode and cathode work functions, specifically aligning them with the negative and positive energy levels of polyradicals and carbon quantum dots, is vital to maximize the on/off current ratio and ensure flash operation in these devices based on organic neutral radicals in a nanostructured environment.
References
[1] F. Xu, H. Xu, X. Chen, D. Wu, Y. Wu, H. Liu, C. Gu, R. Fu, D. Jiang, Angew. Chem. Int. Ed. 54, 6814 (2015)
[2] Y. Ji, J. Hu, M. Lanza, IEEE Nanotechnol. Mag. 9, 12 (2015)
[3] S. Ezugwu, J. A. Paquette, V. Yadav, J. B. Gilroy, G. Fanchini, Advanced El. Materials 2, 1600253 (2016)
[4] J. A. Paquette, S. Ezugwu, V. Yadav, G. Fanchini, J. B. Gilroy, J. Polym. Sci., Part A: Polym. Chem. 54, 1803 (2016).
[5] J. Park, H. Shah, V. Wong, P. Bazylewski,G. Fanchini, Carbon, to appear, (2019)
Biographical Sketch
Professor Giovanni Fanchini is an Associate Professor in the Department of Physics and Astronomy and Department of Chemistry at Western University in London, Ontario, and holds a Canada Research Chair in Carbon-based Nanomaterials and Nanooptoelectronics.
He is exploring new, cheap and more user-friendly ways to create, manipulate and test electronic and optical nano-devices. Fanchini's devices are assembled from plastics and other low-cost organic materials, using techniques that involve disolving the materials in droplets of various liquids, from which the nano-devices are 'traced,' like pictures drawn from ink on the tip of a pen.
Fanchini’s laboratory is a nano-optoelectronics shop fully equipped to develop prototype nano-devices that could dramatically improve, and even completely transform, electronic devices we use every day, such as our mobile phones and personal computers.