High-Q Gold and Silicon Nitride Bilayer Nanostrings

TL;DR

This paper demonstrates that adding a gold overlayer to silicon nitride nanostrings maintains high quality factors and enhances molecular sensing capabilities, while enabling electrical control of internal stresses and resonant actuation.

Contribution

It introduces a bilayer nanostring design with gold that preserves high-Q performance and adds electrical control and actuation methods.

Findings

Gold overlayer does not reduce the Q factor.

The bilayer nanostrings are sensitive to molecular bonding.

AC thermoelastic actuation effectively drives resonant motion.

Abstract

Low-mass, high-Q, silicon nitride nanostrings are at the cutting edge of nanomechanical devices for sensing applications. Here we show that the addition of a chemically functionalizable gold overlayer does not adversely affect the Q of the fundamental out-of-plane mode. Instead the device retains its mechanical responsiveness while gaining sensitivity to molecular bonding. Furthermore, differences in thermal expansion within the bilayer give rise to internal stresses that can be electrically controlled. In particular, an alternating current excites resonant motion of the nanostring. This AC thermoelastic actuation is simple, robust, and provides an integrated approach to sensor actuation.