Imaging the mode shapes of microdrum resonators

Imaging the mode shapes of microdrum resonators

Slim, J.J.

Venstra, W.J. (mentor)
Davidovikj, D. (mentor)
Dubbeldam, J.L.A. (mentor)

Applied Sciences

Quantum Nanoscience

Molecular Electronics and Devices

2015-02-19

A setup was built to measure the local frequency response of (graphene) microdrums in order to image mode shapes. To this end, a laser interferometer that measures the local deflection of a microdrum was equipped with a very precisely movable sample stage. The setup was used to image the mode shapes of a single few layer graphene microdrum, consisting of a graphene flake suspended over a cavity. The local frequency response and accompanying mode shapes of this drum were successfully imaged under three different actuation mechanisms: 1) electrostatic actuation by using a gate electrode at the bottom of the cavity; 2) optothermal actuation by periodic heating from an actuation laser, inducing periodic thermal contractions and expansions; and 3) by thermally induced Brownian motion. The mode shapes of the graphene drum under electrical actuation and Brownian motion were consistent and resembled those predicted by membrane or plate theory, but their eigen frequencies did not match up with either of these regimes. This might be an indication that the drum is in a cross-over regime. It might also be explained by impurities in the drum surface, supported by an atomic force microscopy (AFM) image of the drum surface. The mode shapes of the graphene drum under optothermal actuation had different features, but this might be caused by the fact that the actuation laser was scanned along with the measurement laser in this scheme.

mode shapes
graphene
microdrum
NEMS
laser interferometry
spatial scanning
Brownian motion

http://resolver.tudelft.nl/uuid:0d830ea8-7895-46f5-8262-204d9d09df53

2016-01-01

Student theses

bachelor thesis

(c) 2015 Slim, J.J.