Monolithic three-dimensional hafnia-based artificial nerve system

Abstract

Artificial nerve systems that mimic the tactile perception ability of human skin could be adopted in the realization of devices for a hyperconnected society, including prosthetic devices, interfaces for virtual reality, and smart sensors. The system consists of a pressure sensor, memory, and signal processing circuit, which possess the capability of generating sensory neuron-like signals. Although technological advances have been made in semiconductor-based memory and transistors over the decades, sensor technology is still relying on micro-electromechanical systems, which are hard to realize miniaturization/high-density and high-performance technology. Here, we demonstrate a monolithic three-dimensional integrated artificial nerve on the basis of ferroelectric HfxZr1-xO2 for use in the core element of neuromorphic memory and a self-powered piezoelectric pressure sensor. The morphotropic phase boundary (MPB) state of hafnia film was formed between orthorhombic and tetragonal phases for high piezoelectric performance. The MPB-based sensor was integrated with self-rectifying ferroelectric tunnel junction memory and silicon-based ring oscillator. We realized a frequency-modulated pulse-like synaptic signal with pressure detection ability over a wide range of 1–50 kPa and a good sensitivity of 0.35 mV/kPa. Also, we demonstrate the real-time frequency-modulated operation of the artificial nerve system by adjusting the functional properties of the hafnia films.