Optoelectronic synapses using vertically aligned graphene/diamond heterojunctions

The present work demonstrates that vertically aligned graphene (VG)/diamond heterojunctions can function as optoelectronically-controllable synapses, which are connection parts of neurons and key elements for the memory functions of human brain. These junctions mimic several of the fundamental characteristics of biological synapses, including producing an excitatory postsynaptic current (EPSC), exhibiting a transition from short-term memory (STM) to long-term memory (LTM) states, and paired pulse facilitation (PPF), all of which are optically controllable. These junctions also exhibit photo-sensing properties and photo-controllable synaptic plasticity, meaning that they have similar functions as occur in the human brain and retina. Arrays fabricated from these junctions were found to function as image sensors that could provide an optical memory function and selectively memorize information depending on the relative importance of the data. These results are expected to assist in the realization of neuromorphic optical computers simulating human visual memory systems that are modulated by specific interests.