Towards next-gen computers: Mimicking brain functions with graphene-
diamond junctions
Scientists mimic the brain's functions with junctions between vertically aligned graphene and diamond

Date:
August 4, 2021
Source:
Nagoya University
Summary:
The human brain holds the secret to our unique personalities. But
did you know that it can also form the basis of highly efficient
computing devices? Researchers recently showed how to do this,
through graphene- diamond junctions that mimic some of the human
brain's functions.



FULL STORY ==========================================================================
The human brain holds the secret to our unique personalities. But did
you know that it can also form the basis of highly efficient computing
devices? Researchers from Nagoya University, Japan, recently showed
how to do this, through graphene-diamond junctions that mimic some of
the human brain's functions.


==========================================================================
But, why would scientists try to emulate the human brain? Today, existing computer architectures are subjected to complex data, limiting their
processing speed. The human brain, on the other hand, can process highly complex data, such as images, with high efficiency. Scientists have,
therefore, tried to build "neuromorphic" architectures that mimic the
neural network in the brain.

A phenomenon essential for memory and learning is "synaptic plasticity,"
the ability of synapses (neuronal links) to adapt in response to an
increased or decreased activity. Scientists have tried to recreate
a similar effect using transistors and "memristors" (electronic
memory devices whose resistance can be stored). Recently developed light-controlled memristors, or "photomemristors," can both detect light
and provide non-volatile memory, similar to human visual perception and
memory. These excellent properties have opened the door to a whole new
world of materials that can act as artificial optoelectronic synapses!
This motivated the research team from Nagoya University to design
graphene- diamond junctions that can mimic the characteristics of
biological synapses and key memory functions, opening doors for
next-generation image sensing memory devices. In their recent study
published in Carbon, the researchers, led by Dr.

Kenji Ueda, demonstrated optoelectronically controlled synaptic functions
using junctions between vertically aligned graphene (VG) and diamond. The fabricated junctions mimic biological synaptic functions, such as the production of "excitatory postsynaptic current" (EPSC) -- the charge
induced by neurotransmitters at the synaptic membrane -- when stimulated
with optical pulses and exhibit other basic brain functions such as the transition from short-term memory (STM) to long-term memory (LTM).

Dr. Ueda explains, "Our brains are well-equipped to sieve through the information available and store what's important. We tried something
similar with our VG-diamond arrays, which emulate the human brain when
exposed to optical stimuli." He adds, "This study was triggered due to a discovery in 2016, when we found a large optically induced conductivity
change in graphene- diamond junctions." Apart from EPSC, STM, and LTM,
the junctions also show a paired pulse facilitation of 300% -- an increase
in postsynaptic current when closely preceded by a prior synapse.

The VG-diamond arrays underwent redox reactions induced by fluorescent
light and blue LEDs under a bias voltage. The researchers attributed this
to the presence of differently hybridized carbons of graphene and diamond
at the junction interface, which led to the migration of ions in response
to the light and in turn allowed the junctions to perform photo-sensing
and photo- controllable functions similar to those performed by the brain
and retina. In addition, the VG-diamond arrays surpassed the performance
of conventional rare- metal-based photosensitive materials in terms of photosensitivity and structural simplicity.

Dr. Ueda says, "Our study provides a better understanding of the working mechanism behind the artificial optoelectronic synaptic behaviors, paving
the way for optically controllable brain-mimicking computers better information- processing capabilities than existing computers." The
future of next-generation computing may not be too far away! ========================================================================== Story Source: Materials provided by Nagoya_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Y. Mizuno, Y. Ito, K. Ueda. Optoelectronic synapses using vertically
aligned graphene/diamond heterojunctions. Carbon, 2021; 182:
669 DOI: 10.1016/j.carbon.2021.06.060 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210804123628.htm

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