Nanographene charge trapping memory could further miniaturize flash

November 5, 2015 by Lisa Zyga, feature

(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
(—Flash memory—the data storage method often used in phones, computers, and other devices—is continually being miniaturized in order to improve device performance. In an attempt to reduce the short-circuiting that often occurs as memory cells become smaller and more closely packed, researchers have been investigating graphene-based charge trapping memory as an alternative to the traditional floating gate memory. Now in a new paper, researchers have developed a nanographene-based charge trapping memory that exhibits some of the best performance statistics for any such device reported to date.

The researchers, led by Dongxia Shi and Guangyu Zhang at the Chinese Academy of Sciences in Beijing (Zhang is also with the Collaborative Innovation Center of Quantum Matter in Beijing), have published a paper on the new memory device in a recent issue of Nanotechnology.

"As we all know, we are in an era of information explosion," Jianling Meng, from the Chinese Academy of Sciences and first author of the paper, told "To improve data storage, it is necessary to decrease the footprint of a single node in order to achieve a high density of . Thus, it is a research hot point to keep shrinking flash memories. The biggest advantage for phones and computers having smaller flash memories is a larger storage capacity. Also, smaller can improve the program/erase speed of the data."

In general, shrinking the conventional floating gate memory cell is problematic because it causes short circuits. This happens because the floating gates where the electrons are stored are conductors, and so electrons can easily flow between them when the tiny cells are too close together. An advantage of charge trapping memory is that the charge trapping layer where the electrons are stored is an insulator, so shrinking these cells does not cause short circuits nearly to the extent that it does in memory cells.

In a charge trapping memory, electrons and other charge carriers are stored (or "trapped") in tiny defects in the graphene, which the researchers call "nanographene islands." The more nanographene islands, the more charge that can be stored, resulting in a higher memory capacity.

In the new study, the researchers developed a method for fabricating nanographene with a density estimated at more than a trillion (1012) nanographene islands per square centimeter. Their strategy uses a technique called plasma etching to create large numbers of defects as well as extended defects along the edges of the main defects.

The large number of charge trapping sites provided by the defects enabled the researchers to fabricate a memory device with a very competitive memory performance. One measure of large capacitance is a large memory window, which indicates that a large number of have been trapped. Tests here revealed that the new memory has the largest ever memory window (9 volts) reported to date for a graphene-based charge trapping memory. In addition, this large memory window was maintained even after 1,000 program/erase cycles.

Overall, the researchers hope that this high-density memory will provide a path toward shrinking flash to even smaller scales.

"Our future research plan in this area is to realize a footprint as small as the tip of an atomic force microscope," Meng said.

Explore further: Graphene quantum dot flash memories look promising for data storage

More information: Jianling Meng, et al. "Nanographene charge trapping memory with a large memory window." Nanotechnology. DOI: 10.1088/0957-4484/26/45/455704

Related Stories

Organic flash memory developed

December 17, 2009

( -- Researchers at the University of Tokyo have developed a non-volatile memory that has the same basic structure as a flash memory but is made from cheap, flexible, organic materials.

Elpida and Spansion develop 4-Gigabit NAND flash memory

September 2, 2010

Elpida Memory and Spansion today announced they have created the industry's first charge-trapping 1.8 V, 4-gigabit SLC (Single Level Cell) NAND Flash memory. This NAND memory, based on Spansion's MirrorBit charge-trapping ...

Recommended for you

In small groups, people follow high-performing leaders

February 21, 2019

While the "wisdom of the crowd" shapes the behavior of large groups of people, less is known about small-group dynamics and how individuals interact to make decisions, particularly when it comes to the emergence of leaders, ...

Researchers make coldest quantum gas of molecules

February 21, 2019

JILA researchers have made a long-lived, record-cold gas of molecules that follow the wave patterns of quantum mechanics instead of the strictly particle nature of ordinary classical physics. The creation of this gas boosts ...

Sculpting stable structures in pure liquids

February 21, 2019

Oscillating flow and light pulses can be used to create reconfigurable architecture in liquid crystals. Materials scientists can carefully engineer concerted microfluidic flows and localized optothermal fields to achieve ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.