Journal Article ReLU activation neuron TRNG arc discharge artificial intelligence training banknote bipolar photo response deep neural network ferroelectric transistor gas sensors impact ionization transistor initiated chemical vapor deposition nanostructured transition metal oxide neuromorphic computing neuromorphic devices papertronics physical unclonable functions, ultrafast synthesis physically unclonable function security devices spiking neural network spiking neuron synaptic devices universal synthesis unsupervised learning vanishing gradient problem