ALD employed in nanographene charge trapping memory with a large memory window

A leading research centre for grapehene devices is Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Science. They have recently published a paper on Nanographene charge trapping memory. Here they use a 15 nm thick Al2O3, deposited by ALD, to act as a tunnelling layer and blocking layer, respectively (see abstract below).

According to the website: The research groups led by Prof. ZHANG Guangyu is recently focusing on graphene nanostructure fabrications and the related electrical transport studies and has:

Schematic of the graphene edge lithography. The process includes selectively ALD of Al₂O₃/HfO₂ on graphene edges, dry etching of the unprotected graphene and KOH etching of the metal oxides.(Image by ZHANG Guangyu et al )

• reported a highly anisotropic dry-etching technique in graphene basal plane for the first time [Advanced Materials 22, 4014, (2010)]] http://onlinelibrary.wiley.com/doi/10.1002/adma.201000618/pdf
• combined this technique with artificial-defects engineering for well-controlled top-down cutting of graphene nanostructures with zigzag-edges and sub-10-nm feature sizes [Advanced Materials 23, 3061, (2011)]. http://onlinelibrary.wiley.com/doi/10.1002/adma.201100633/pdf
• studied Raman scattering of graphene nanoribbons with Hydrogen-terminated zigzag edges and found the electron-phonon coupling in these unique structures [Nano letters 11, 4083-4088 (2011)]. http://pubs.acs.org/doi/abs/10.1021/nl201387x

Nanographene charge trapping memory with a large memory window

Jianling Meng, Rong Yang, Jing Zhao, Congli He, Guole Wang, Dongxia Shi and Guangyu Zhang

2015 Nanotechnology 26 455704
http://dx.doi.org/10.1088/0957-4484/26/45/455704

 Left, AFM images of nanographen films showing a high density of nanographen islands. Right, the stack and structure of the nanographene charge tarpping memory cell (PhysOrg: http://phys.org/news/2015-11-nanographene-memory-miniaturize.html)

(Left) Atomic force microscope image of the nanographene film with a high density of nanographene islands, which provide more charge-trapping sites to increase store capacity. (Right) Structure of the nanographene-based charge trapping memory. Credit: Meng, et al. ©2015 IOP Publishing

Read more at: http://phys.org/news/2015-11-nanographene-memory-miniaturize.html#jCp

(Left) Atomic force microscope image of the nanographene film with a high density of nanographene islands, which provide more charge-trapping sites to increase store capacity. (Right) Structure of the nanographene-based charge trapping memory. Credit: Meng, et al. ©2015 IOP Publishing

Read more at: http://phys.org/news/2015-11-nanographene-memory-miniaturize.html#jCp

Nanographene is a promising alternative to metal nanoparticles or semiconductor nanocrystals for charge trapping memory. In general, a high density of nanographene is required in order to achieve high charge trapping capacity. Here, we demonstrate a strategy of fabrication for a high density of nanographene for charge trapping memory with a large memory window. The fabrication includes two steps: (1) direct growth of continuous nanographene film; and (2) isolation of the as-grown film into high-density nanographene by plasma etching. Compared with directly grown isolated nanographene islands, abundant defects and edges are formed in nanographene under argon or oxygen plasma etching, i.e. more isolated nanographene islands are obtained, which provides more charge trapping sites. As-fabricated nanographene charge trapping memory shows outstanding memory properties with a memory window as wide as ~9 V at a relative low sweep voltage of ±8 V, program/erase speed of ~1 ms and robust endurance of >1000 cycles. The high-density nanographene charge trapping memory provides an outstanding alternative for downscaling technology beyond the current flash memory.