Graphene quantum dot flash memories look promising for data storage

Jun 18, 2014 by Lisa Zyga feature
(a) Schematic diagram and (b) image of a graphene quantum dot flash memory. Charge storage in discrete charge traps, such as graphene quantum dots, offers the potential for high-density data storage. Credit: Joo, et al. ©2014 IOP Publishing

(Phys.org) —Today's commercial flash memories usually store data as electric charge in polysilicon layers. Because polysilicon is a single continuous material, defects in the material can interfere with the desired charge movement, which can limit data retention and density.

To overcome this problem, researchers have recently been working on storing charge in discrete charge traps, such as nanocrystals, instead of polysilicon layers. Since discrete charge trap materials have the advantage of preventing unwanted charge movement as a result of their lower sensitivity to local defects, they offer the potential for high-density flash memories.

Now in a new study, scientists have used graphene quantum dots instead of nanocrystals as the discrete charge trap material. The researchers, Soong Sin Joo, et al., at Kyung Hee University and Samsung Electronics, both in Yongin, South Korea, have published their paper on graphene quantum dot in a recent issue of Nanotechnology.

Although graphene in general is widely known as an attractive material for next-generation electronics and photonics because of its unique properties, the development of graphene is still at an early stage. Graphene quantum dots in particular are very new materials. As bits of graphene extracted from bulk carbon, graphene quantum dots can be engineered with specific electronic and optical properties for different purposes.

Here, the researchers prepared graphene quantum dots of three different sizes (6, 12, and 27 nm diameters) between silicon dioxide layers. The researchers found that the memory properties of the dots differ depending on their sizes. For instance, while the 12-nm dots exhibit the highest program speed, the 27-nm dots exhibit the highest erase speed, as well as the highest stability.

"This is the first report of charge-trap flash nonvolatile memories made by employing structurally characterized graphene quantum dots, even though their nonvolatile memory properties are currently below the commercial standard," coauthor Suk-Ho Choi at Kyung Hee University told Phys.org. "Actually, this is first successful application of graphene quantum dots in practical devices, including electronic and optical devices, as far as I know, even though there are many reports on physical and chemical characterizations of graphene quantum dots."

As flash memory devices in their early stages of development, the graphene quantum dot memories demonstrate a promising performance, with an electron density comparable to that of memory devices based on semiconductor and metal nanocrystals. The researchers hope that future improvements to the devices will lead to enhanced performance and new applications.

"If flexible dielectrics (insulators) are used instead of silicon dioxides as tunnel and control barriers on plastic substrates, then they can be used in flexible (or wearable) electronic devices," Choi said. "Metal nanoparticles also offer several advantages similar to graphene , such as higher density of states, flexibility in choosing the work function, etc., for charge-trap flash nonvolatile memories, but may potentially degrade the device performance due to their thermal instabilities and are not useful for transparent and flexible electronics and photonics."

Explore further: Resonant energy transfer from quantum dots to graphene

More information: Soong Sin Joo, et al. "Graphene-quantum-dot nonvolatile charge-trap flash memories." Nanotechnology 25 (2014) 255203 (6pp). DOI: 10.1088/0957-4484/25/25/255203

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MR166
5 / 5 (1) Jun 18, 2014
Many articles on phys.org promote the possibility of wearable electronic devices. Why would anyone want such a thing? I can see a lot of problems with a wearable device and no real advantage.
Captain Stumpy
5 / 5 (1) Jun 18, 2014
Many articles on phys.org promote the possibility of wearable electronic devices. Why would anyone want such a thing?
@mr166
that really depends on the item you are talking about, really. Heart monitor that is wearable, lightweight etc is good for exercise as well as people with cardiac issues and need regular checks
build in B/P, O2 stats and even glucose levels and you have a portable, lightweight lab doing regular checks for you so that you don't have to stop what you are doing, find your bag with your stick pins/sphygmomanometer/glucose meter etc...assuming you didn't forget it AGAIN

There are other applications that could be beneficial, not only to the injured/handicapped but to, say, the hiker for accessing maps/emergency response with Sat-Com link

another thought: a child wearing their light weight hidden anti-pedo or anti-abduction lo-jacked underwear/shirt/shoes?

that's just off the cuff speculation. I can think of plenty more things I'd consider useful
Captain Stumpy
not rated yet Jun 18, 2014
I can see a lot of problems with a wearable device and no real advantage
@mr166
Yes, I can also see many problems that might crop up... but there could be huge advantages considering the above mentioned possibilities... that is not to mention other uses like Military/Law enforcement tracking/monitoring or use in Jail/prison monitoring/tracking... less direct personal invasions of privacy yet more detailed direct monitoring of convicts.

most importantly, I would say that (if they can work out the bugs) the safety of health and security of important objects would be some of the bast uses, but I also see incorporating a great deal of "frills" like integrated phone/data management/etc (of which I really don't see much use for)

how much would a parent pay to keep their kids safe with wearable lo-jack clothing?

mind you I am just babbling about fringe possibilities that I can see being useful...
this is strictly IMHO

MR166
5 / 5 (1) Jun 19, 2014
Thanks Capt.. I suppose that the device would have to be encapsulated in some sort of clear plastic to survive the washing machine and resist tearing.