Reconfigurable nonlinear photonic activation function for photonic neural network based on non-volatile opto-resistive RAM switch

Photonic neural network has been sought as an alternative solution to surpass the efficiency and speed bottlenecks of electronic neural network.Despite that the integrated Mach-Zehnder Interferometer(MZI)mesh can perform vector-matrix multiplication in photonic neural network,a programmable in-situ nonlinear activation function has not been proposed to date,suppressing further advancement of photonic neural network.Here,we demonstrate an efficient in-situ nonlinear accelerator comprising a unique solution-processed two-dimensional(2D)MoS2 Opto-Resistive RAM Switch(ORS),which exhibits tunable nonlinear resistance switching that allow us to introduce nonlinearity to the photonic neuron which overcomes the linear voltage-power relationship of typical photonic components.Our reconfigurable scheme enables implementation of a wide variety of nonlinear responses.Furthermore,we confirm its feasibility and capability for MNIST handwritten digit recognition,achieving a high accuracy of 91.6%.Our accelerator constitutes a major step towards the realization of in-situ photonic neural network and pave the way for the integration of photonic integrated circuits(PIC).

Threshold voltage modulation in monolayer MoS_(2) field-effect transistors via selective gallium ion beam irradiation

Electronic regulation of two-dimensional(2 D)transition metal dichalcogenides(TMDCs)is a crucial step towards next-generation optoelectronics and electronics.Here,we demonstrate controllable and selective-area defect engineering in 2D molybdenum disulfide(MoS_(2))using a focused ion beam with a low-energy gallium ion(Ga^(+))source.We find that the surface defects of MoS_(2)can be tuned by the precise control of ion energy and dose.Furthermore,the fieldeffect transistors based on the monolayer MoS_(2)show a significant threshold voltage modulation over 70 V after Ga+irradiation.First-principles calculations reveal that the Ga impurities in the monolayer MoS_(2)introduce a defect state near the Fermi level,leading to a shallow acceptor level of 0.25 eV above the valence band maximum.This defect engineering strategy enables direct writing of complex pattern at the atomic length scale in a controlled and facile manner,tailoring the electronic properties of 2D TMDCs for novel devices.