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In-situ observation of low-power nano-synaptic response in graphene oxide using conductive atomic force microscopy

  • Hui, F
  • Liu, P
  • Hodge, S
  • Carey, T
  • Wen, C
  • Torrisi, F
  • Galhena, T
  • Tomarchio, F
  • Lin, Y
  • Moreno, E
  • Roldan, J
  • Koren, E
  • Ferrari, A
  • Lanza, M
Publication Date
Apr 12, 2021
Spiral - Imperial College Digital Repository


Multiple studies have reported the observation of electro-synaptic response in different metal/insulator/metal devices; however, most of them analysed large (>1 µm2) devices that do not meet the integration density required by the industry (1010 devices/mm2). Some studies employed a scanning tunnelling microscope (STM) to explore nano-synaptic response in different materials, but in this setup there is a nanogap between the insulator and one of the metallic electrodes (i.e. the STM tip), which is not present in real devices. Here we show how to use a conductive atomic force microscope (CAFM) to explore the presence and quality of nano-synaptic response in confined areas <500 nm2. For this study, we selected graphene oxide (GO) due to its easy fabrication and excellent electrical properties. Our experiments indicate that metal/GO/metal nano-synapses exhibit potentiation and paired pulse facilitation with low write current levels <1 µA (i.e. power consumption ~3 μW), controllable excitatory post-synaptic currents and long-term potentiation and depression. Our results provide a new method to explore nano-synaptic plasticity at the nanoscale, and point GO as an important candidate material for the fabrication of ultra-small (<500 nm2) electronic synapses fulfilling the integration density requirements of neuromorphic systems.

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