Capacitive Spring Softening in Single-Walled Carbon Nanotube Nanoelectromechanical Resonators

TL;DR

This paper demonstrates capacitive spring softening in single-walled carbon nanotube NEM resonators with dual-gate tuning, revealing mode-dependent effects and potential for nonlinear device applications.

Contribution

It introduces a dual-gate design enabling the observation of capacitive spring softening and mode differentiation in SWNT resonators.

Findings

Downward resonance frequency shift with increasing side-gate voltage

In-plane vibrational modes show stronger softening than out-of-plane modes

Dual-gate configuration allows mode differentiation and nonlinear operation potential

Abstract

We report the capacitive spring softening effect observed in single-walled carbon nanotube (SWNT) nanoelectromechanical (NEM) resonators. The nanotube resonators adopt dual-gate configuration with both bottom-gate and side-gate capable of tuning the resonance frequency through capacitive coupling. Interestingly, downward resonance frequency shifting is observed with increasing side-gate voltage, which can be attributed to the capacitive softening of spring constant. Furthermore, in-plane vibrational modes exhibit much stronger spring softening effect than out-of-plan modes. Our dual-gate design should enable the differentiation between these two types of vibrational modes, and open up new possibility for nonlinear operation of nanotube resonators.