Abstract:
Introduction
In the past few decades, computer
vision (CV) has achieved considerable progress with advanced intelligent
algorithms and computing hardware. [1-3] However,
most image-data-based processing algorithms require a large number of
parameters that are usually stored in the memory module, which will
cause frequent data transfer between memory and processor when the
systems receive sensor information.[4, 5] Inspired
by the in-memory computing feature in the human brain and combined with
modern deep neural networks (DNN), the crossbar arrays made of emerging
nonvolatile memories (eNVM) are implemented to accelerate the
multiply-accumulate (MAC) operations which dominated mostly in
DNN.[6-10, 37] In addition to the synaptic devices
exploration, recently, as also the core components of neuromorphic
computing, there was plenty of research about searching for the hardware
implementation of neurons based on emerging materials and
devices.[11-14] For instance, the memristive
neurons, including Mott memristors,[15-19] redox
memristors,[20, 21] phase-change
memristors,[22]etc, all of them can emulate the
leaky integrate-and-fire (LIF) function of biological neurons.
However, the device type and materials between the hardware
implementation of synapses and neurons usually differ from each other,
which will cause additional fabrication costs in large-scale integration
and severe limits on the scalability for further
applications.[15, 21] Nowadays, many researchers
put forward the idea of reconfiguring device’s functions on the same
hardware platform.[14, 23-25] One of the studies
made use of reconfigurable synaptic and neuronal functions in the
V/VOx/HfWOx/Pt memristors for spiking
neural network,[23] manipulating the ion
distributions in HfWOx memristors to enable devices
working on different modes.
Moreover, inspired by how neurotransmitters modulate human neural
networks, investigators tend to exploit moveable ions, such as
H+, Li+ and
O2-,[24, 26-30] to regulate the
electrical properties of materials, which has made neuromorphic hardware
advance a big step. For instance, by changing the local distribution of
hydrogen ions, researchers have demonstrated the reconfigurable
perovskite nickelate electronics for reservoir computing and incremental
learning.[24]
In a complete neuromorphic system, it is also critical to pre-process
external information after sensing from the outside world. Most of the
information humans receive is obtained through vision, simulating the
vision systems of humans is of great importance to the artificial
perception system.[31] There were also many
explorations about building an artificial vision system to process the
data correlated with vision. However, little effort had been devoted to
combining the reconfiguration ideas with energy-efficient neuromorphic
vision systems, which can help reduce complexity of the system.
Inspired by ionic regulation methods and reconfiguring advantages, we
propose an energy-efficient vision system based on reconfigurable
ion-modulated memtransistors. With different stimuli ranges, the
temporal scales of ion dynamics inside the devices can be well
controlled. As for the short-term dynamics, the accumulation effect can
help filter the random noises and enhance the original patterns
simultaneously, which was demonstrated in the reconstruction from a set
of noisy images. After that, we investigate the relationship between the
channel conductance changes and stimuli amplitudes. The observed
nonlinear relation can both be used for softplus-like neurons and
filtering units. By changing external stimuli, long-term channel
conductance modulation can also be achieved to implement weight storage.
Based on the above considerations, we present an architecture for
neuromorphic vision systems based on the reconfigurable ion-modulated
memtransistors. In the system-level performance demonstration, an
artificial neural network (ANN) was implemented to recognize the
Fashion-MNIST datasets where the filtering units, synapse weights and
activation neurons were all based on the ion-modulated memtransistors.
Through detailed analysis and testing of the mapping strategies and
noises on the network-level performances, we prove that the neuromorphic
vision system can help recognize images in practice with relatively high
accuracy and improved robustness.