Side ionic-gated perovskite/graphene heterojunction synaptic transistor with bipolar photoresponse for neuromorphic computing

By combining the good charge transport property of graphene and the excellent photo-carrier generation char-acteristic of perovskite nanocrystal,we propose and demonstrate an ionic-gated synaptic transistor based on CsPbBr_(3)∕graphene heterojunction for bipolar photoresponse.Controlling the potential barrier of the CsPbBr_(3)∕graphene heterojunction by the ionic-gate of the electrical double-layer effect can promote the sepa-ration of photogenerated carriers and effectively retard their recombination.Using the ionic-gate-tunable Fermi level of graphene and the pinning effect of perovskite nanocrystal,the bipolar photocurrent responses correspond-ing to the excitatory and inhibitory short-term and long-term plasticity are realized by adjusting the negative gate bias.A series of synaptic functions including logic operation,Morse coding,the optical memory and electrical erasure effect,and light-assisted re-learning have also been demonstrated in an optoelectronic collaborative path-way.Furthermore,the excellent optical synaptic behaviors also contribute to the handwritten font recognition accuracy of-95%in artificial neural network simulations.The results pave the way for the fabrication of bipolar photoelectric synaptic transistors and bolster new directions in the development of future integrated human ret-inotopic vision neuromorphic systems.

Multimodal MEMS vibration energy harvester with cascaded flexible and silicon beams for ultralow frequency response

Scavenged energy from ambient vibrations has become a promising energy supply for autonomous microsystems.However,restricted by device size,most MEMS vibration energy harvesters have much higher resonant frequencies than environmental vibrations,which reduces scavenged power and limits practical applicability.Herein,we propose a MEMS multimodal vibration energy harvester with specifically cascaded flexible PDMS and"zigzag"silicon beams to simultaneously lower the resonant frequency to the ultralow-frequency level and broaden the bandwidth.A two-stage architecture is designed,in which the primary subsystem consists of suspended PDMS beams characterized by a low Young's modulus,and the secondary system consists of zigzag silicon beams.We also propose a PDMS lift-off process to fabricate the suspended flexible beams and the compatible microfabrication method shows high yield and good repeatability.The fabricated MEMS energy harvester can operate at ultralow resonant frequencies of 3 and 23 Hz,with an NPD index of 1.73μW/cm^(3)/g^(2)@3 Hz.The factors underlying output power degradation in the low-frequency range and potential enhancement strategies are discussed.This work offers new insights into achieving MEMS-scale energy harvesting with ultralow frequency response.