Neuromorphic Photoresponse in Ultrathin SnS₂-Based Field Effect Transistor

Area of Science:

• Materials Science
• Condensed Matter Physics
• Neuroscience

Background:

• Neuromorphic computing aims to emulate biological neural networks for advanced AI.
• Two-dimensional (2D) materials offer tunable properties for neuromorphic device applications.
• Tin disulfide (SnS2) is a promising 2D material for electronic and optoelectronic devices.

Purpose of the Study:

• To characterize the electrical and optoelectronic properties of SnS2 field-effect transistors (FETs).
• To investigate the mechanisms behind persistent photoconductivity and synaptic plasticity in SnS2 FETs.
• To explore the potential of SnS2 for neuromorphic computing applications.

Main Methods:

• Electrical and optoelectronic characterization of a back-gated SnS2 FET.
• Measurements conducted at varying temperatures (80-380 K), pressures (ambient to 10^-4 mbar), and illumination conditions (420-800 nm laser).
• Analysis of trap states and ambient adsorbates to understand observed phenomena.

Main Results:

• Observed responsivity peaks up to ~100 A/W and persistent photoconductivity.
• Current retention after illumination ranged from 0% to 30% of the dark current.
• Demonstrated tunable synaptic plasticity (weight changes from 0.001 to 3000) by exploiting trap states.

Conclusions:

• Microscopic mechanisms, including trap states and adsorbates, govern plasticity in SnS2.
• Temperature and gate voltage effectively modulate synaptic plasticity, enabling short-term to long-term behavior transitions.
• SnS2 shows robustness under realistic conditions, paving the way for its integration into neuromorphic architectures.