Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

Thomas Metcalf,Matthew Robert Abernathy,Xiao Liu

doi:10.1590/1980-5373-mr-2017-0875

Thomas Metcalf, Matthew Robert Abernathy + Show 1 more

Open Access

https://doi.org/10.1590/1980-5373-mr-2017-0875

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Abstract

We evaluate two methods to improve the background internal friction of the Double Paddle Oscillator (DPO), which has a nominal low temperature value of Q-1 ≈ 2×10-8. We find that annealing the DPO in vacuum at 300°C for 3 hours systematically reduced Q-1 at all temperatures and revealed a 100K internal friction peak by permanently removing it. We also find a striking decrease of low temperature Q-1 as the DPO geometry is altered through extended etching. This decrease is evaluated via Finite Element Method modeling in terms of mode mixing and attachment loss.

Highlights

For more than 40 years, the internal frictions of thin film materials have been measured by depositing the films onto resonators with high quality factors and measuring the change of both resonant frequency and quality factor of the resonator.[1]
One resonator which provides an excellent platform for thin film internal friction measurements is the double paddle oscillator, or Double Paddle Oscillator (DPO).[2,3]
A companion resonator, termed the Young’s Modulus Resonator (YMR), uses a similar scheme for flexural deformations,[4] and the annealing results discussed below should apply to the YMR as well

Summary

Introduction

For more than 40 years, the internal frictions of thin film materials have been measured by depositing the films onto resonators with high quality factors and measuring the change of both resonant frequency and quality factor of the resonator.[1]. One resonator which provides an excellent platform for thin film internal friction measurements is the double paddle oscillator, or DPO.[2,3] It is pictured in the inset to Figure 1. The 8th mechanical resonance (in ascending order of frequency) of this resonator is referred to as the 2nd anti-symmetric mode, or AS2 It is an audiofrequency mode with a resonant frequency between 5 kHz and 7 kHz. The out-of-plane motion of this mode is illustrated in the color scale and wireframe of the inset to Figure 1. We discuss two systematic and repeatable effects which contribute to these improved quality factors

Fabrication and Measurement

Annealing

Etching Geometry

Findings

Conclusions