Large electro-opto-mechanical coupling in VO2 neuristors

TL;DR

This paper demonstrates that VO2 neuristors exhibit strong electro-opto-mechanical coupling with high energy efficiency, showing potential for advanced MEMS applications and surpassing traditional piezoelectric and electro-optic materials.

Contribution

The study reveals that VO2 neuristors have significantly enhanced electro-opto-mechanical coupling coefficients, offering a novel, efficient platform for neuromorphic and MEMS technologies.

Findings

Effective piezoelectric coefficient d13* is 660 pm/V.

Electro-optic coefficient r13* is approximately 22 nm/V.

VO2 neuristors outperform conventional materials in energy conversion.

Abstract

Biological neurons are electro-mechanical systems, where the generation and propagation of an action potential is coupled to generation and transmission of an acoustic wave. Neuristors, such as VO2, characterized by insulator-metal transition (IMT) and negative differential resistance, can be engineered as self-oscillators, which are good approximations of biological neurons in the domain of electrical signals. In this study, we show that these self-oscillators are coupled electro-opto-mechanical systems, with better energy conversion coefficients than the conventional electromechanical or electrooptical materials. This is due to the significant contrast in the material's resistance, optical refractive index and density across the induced temperature range in a Joule heating driven IMT. We carried out laser interferometry to measure the opto-mechanical response while simultaneously driving the devices electrically into self-oscillations of different kinds. We analyzed films of various thicknesses, engineered device geometry and performed analytical modelling to decouple the effects of refractive index change vis-a-vis mechanical strain in the interferometry signal. We show that the effective piezoelectric coefficient (d13*) for our neuristor devices is 660 pm/V, making them viable alternatives to Pb-based piezoelectrics for MEMS applications. Furthermore, we show that the effective electro-optic coefficient (r13*) is ~22 nm/V, which is much larger than that in thin-film and bulk Pockels materials.