Frequency-Dependent Piezoresistive Effect in Top-down Fabricated Gold Nanoresistors

TL;DR

This study investigates how the piezoresistive response of gold nanoresistors varies with frequency, revealing a significant increase in gauge factor at higher frequencies, which could impact nanoscale sensor design.

Contribution

It introduces an experimental method to measure frequency-dependent piezoresistive effects in gold nanoresistors fabricated on nanomechanical resonators.

Findings

Gauge factor increases from 3.6 at 4 MHz to 15 at 36 MHz

Frequency-dependent piezoresistive behavior observed in gold nanoresistors

Potential physics discussed for the frequency dependence

Abstract

Piezoresistive strain gauges allow for electronic readout of mechanical deformations with high fidelity. As piezoresistive strain gauges are aggressively being scaled down for applications in nanotechnology, it has become critical to investigate their physical attributes at different limits. Here, we describe an experimental approach for studying the piezoresistive gauge factor of a gold thin-film nanoresistor as a function of frequency. The nanoresistor is fabricated lithographically near the anchor of a nanomechanical doubly-clamped beam resonator. As the resonator is driven to resonance in one of its normal modes, the nanoresistor is exposed to frequency-dependent strains of {$\varepsilon \lesssim 10^{-5}$} in the $4-36~\rm MHz$ range. We calibrate the strain using optical interferometry and measure the resistance changes using a radio-frequency mix-down technique. The piezoresistive gauge factor $\gamma$ of our lithographic gold nanoresistors is $\gamma \approx 3.6$ at 4 MHz, in agreement with comparable macroscopic thin metal film resistors in previous works. However, our $\gamma$ values increase monotonically with frequency and reach $\gamma \approx 15$ at 36 MHz. We discuss possible physics that may give rise to this unexpected frequency dependence.