MSc thesis project proposal
Measuring the resonances of nanopillars through surface acoustic waves
Micro- and nanopillars made of different materials have found extensive applications in various scientific and industrial fields, including energy harvesting, energy storage in batteries, and sensors. For the latter, nanopillars offer two major advantages. First, due to their small volume, their mechanical resonances present large responsivities to external stimuli . Second, the large surface areas of nanopillars in large arrays provide an excellent platform for chemical reactions and the adsorption of analytes .
An important hurdle in the use of nanopillars to build compact sensors is the difficulty in measuring their vibrations without resorting to complex methods that cannot be integrated on the same chip as the nanopillars. An interesting approach is to use acoustic waves propagating through the subsrate to probe the nanopillars vibrations . Surface acoustic waves (SAW) can be easily produced in silicon chips integrating piezoelectric materials, such as aluminium nitride or lithium niobate. The propagation of acoustic waves through the substrate can be characterized by measuring the time delay and acoustic power transmission between two interdigitated transducers (IDT), one for emission and one for reception of SAW. As the SAW propagate through a substrate containing an array of nanopillars, the wave characteristics will be modulated when the frequency approaches the resonances of the nanopillars. This method will allow for measuring the resonances of nanopillars by using simple piezoelectric transducers integrated on chip.
 Wasisto, H. S., Merzsch, S., Stranz, A., Waag, A., Uhde, E., Salthammer, T., & Peiner, E. (2013). Silicon resonant nanopillar sensors for airborne titanium dioxide engineered nanoparticle mass detection. Sensors and Actuators B: Chemical, 189, 146-156.
 Xu, J., Setiono, A., & Peiner, E. (2020). Piezoresistive microcantilever with SAM-modified ZnO-nanorods@ silicon-nanopillars for room-temperature parts-per-billion NO2 detection. ACS Applied Nano Materials, 3(7), 6609-6620.
 Ramakrishnan, N., Nemade, H. B., & Palathinkal, R. P. (2010). Finite element method simulation of a surface acoustic wave hydrogen sensor with palladium nano-pillars as sensing medium. Sensor Letters, 8(6), 824-828.
- Perform a literature review on the topics of nanopillars and SAW devices.
- Design and simulate SAW devices based on aluminum nitride. Simulate the effect of an array of nanopillars on the transmission path of an acoustic delay line, varying the dimensions and design parameters of the nanopillars array.
- Fabricate SAW devices based on aluminum nitride, optimizing the fabrication methods already available at EKL. Implement nanopillars on the SAW devices by standard lithography and etching methods.
- Characterize the resulting devices with electrical measurements.
You must be motivated to learn and apply different techniques for fabricating new devices. Experience with FEM simulation packages such as Comsol is a must. Notions of mechanical resonators or acoustic devices is desirable.
dr. Tomás Manzaneque
Electronic Instrumentation Group
Department of Microelectronics
Last modified: 2022-02-17