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Li CH, Du W, Huang YX, Zou JH, Luo LZ et al. Photonic synapses with ultralow energy consumption for artificial visual perception and brain storage. Opto-Electron Adv 5, 210069 (2022). doi: 10.29026/oea.2022.210069
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Photonic synapses with ultralow energy consumption for artificial visual perception and brain storage
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Abstract
The human visual system, dependent on retinal cells, can be regarded as a complex combination of optical system and nervous system. Artificial retinal system could mimic the sensing and processing function of human eyes. Optically stimulated synaptic devices could serve as the building blocks for artificial retinas and subsequent information transmission system to brain. Herein, photonic synaptic transistors based on polycrystalline MoS2, which could simulate human visual perception and brain storage, are presented. Moreover, the photodetection range from visible light to near-infrared light of MoS2 multilayer could extend human eyes’ vision limitation to near-infrared light. Additionally, the photonic synaptic transistor shows an ultrafast speed within 5 μs and ultralow power consumption under optical stimuli about 40 aJ, several orders of magnitude lower than biological synapses (50 ms and 10 fJ). Furthermore, the backgate control could act as emotional modulation of the artificial brain to enhance or suppress memory function, i.e. the intensity of photoresponse. The proposed carrier trapping/detrapping as the main working mechanism is presented for the device. In addition, synaptic functionalities including short synaptic plasticity, long synaptic plasticity and paired-pulse facilitation could be successfully simulated based on the prepared device. Furthermore, the large difference between short synaptic plasticity and long synaptic plasticity reveals the better image pre-processing function of the prepared photonic synapses. The classical Pavlovian conditioning associated with the associative learning is successfully implemented as well. Therefore, the efficient and rich functionalities demonstrate the potential of the MoS2 synaptic device that integrates sensing-memory-preprocessing capabilities for realizing artificial neural networks with different emotions that mimic human retina and brain.-
Keywords:
- MoS2 synaptic transistors /
- visual perception /
- ultralow power consumption /
- memory
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References
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Li CH, Du W, Huang YX, Zou JH, Luo LZ et al. Photonic synapses with ultralow energy consumption for artificial visual perception and brain storage. Opto-Electron Adv 5, 210069 (2022). doi: 10.29026/oea.2022.210069
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Figure 1.
Optical characterizations of MoS2 synaptic transistors and schematic diagram of human eyes. (a) The optical image of large-area and uniform polycrystalline MoS2. Scale bar: 100 μm. (b) The optical photograph of a MoS2 synaptic transistor array on Si/SiO2 substrate. Scale bar: 500 μm. The corrsponding Raman spectrum (c) and PL spectrum (d) of MoS2. The corresponding Raman mapping around 381.4 cm–1 (e) and PL mapping (f) selected randomly from (a). Scale bar: 8 μm. (g) Schematic diagram of visual perception and information transmission in human brain and corresponding artifical MoS2 synaptic device.
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Figure 2.
Photodetection and spike-duration plasticity of the MoS2 synaptic transistor. Output characteristic curves of the MoS2 synaptic transistor in visible light (a) and NIR light (b). The inset in (b) is the corresponding linear output characteristic curve. (c) The transient current responses triggered by several optical stimulus with different duration of a single pulse, respectively. (d) The EPSC at the pulse width of 5 μs (405 nm, Vds = 1 V). (e) Comparison of single optical pulse width and power consumption among some synaptic devices.
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Figure 3.
STP characteristics of the MoS2 synaptic transistor. (a) The transient current response induced by an optical pulse of 50 ms. (b) The EPSC curves under different laser power densities (pulse width: 100 ms). Inset: The dependence of EPSC with differnent laser power densities (P). (c) The instantaneous current responses triggered by a pair of optical pulses (pulse width = 50 ms, pulse interval Δt = 2 s). The black dashed line represents the initial current in (a) and (c) without optical stimuli. (d) The PPF behaviors at different Δt.
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Figure 4.
LTP characteristics of the MoS2 synaptic transistor. The transient current (a), EPSC (b) and the extracted forgetting curve (c) from (a) after 10, 25, 50, 75 and 100 optical pulses. The transient current (d), A30/A1 (e) and the extracted forgetting curve (f) from (d) triggered by different spike frequency where A30 means the thirtieth EPSC. The black dashed line represents the initial current in (c) and (f) without optical stimuli.
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Figure 5.
Schematic illustration of the Pavlovian conditioning and emotional effect on the MoS2 synaptic transistor. The classical Pavlovian conditioning under one training (E+L) (a) and ten trainings (b). (c) The transient current triggered by 30 optical spikes at the backgate of 0.1 V, 0 V and –0.1 V. (d) The maximum EPSC at different Vg.
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Figure 6.
Neuromorphic imaging simulation. (a) Illustration of neuromorphic letter recognition. The stimulated letter recognition under STP (b), LTP with (c) or without (d) -Vg.
