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Physics and Astronomy
Completed Project

Transition Metal Dichalcogenides as Strain Sensors in Pump-Probe Experiments

Celia Morral ’22, Phyo Pyi Kyaw ’22 and Professor Brian Daly (Physics)

We investigated using an ultrafast pump-probe experiment to image samples by monitoring their optical properties. This process uses a pump laser pulse to excite a rapid thermal change in the sample, creating acoustic pulses in the substrate below. After a certain time, a probe laser pulse measures the change in optical properties at the sample’s surface. Thus far, we have used Aluminum as a transducer to create an acoustic pulse in the sample and to detect the pulse. One of the disadvantages of using Al as a transducer is that it creates low resolution images due to its low sensitivity to strain. Therefore, we conducted literature research to explore the possibility of using a Transition Metal Dichalcogenide (TMD) as the detecting layer in our pump-probe experiment. We were interested in which optical properties (reflectivity or transmissivity) to measure, how many layers of TMD to use, and which TMD (WSe2 or MoS2) would be most effective. We also investigated which phonon modes would get the strongest signal and whether surface acoustic waves could be used to improve image resolution. We found that TMDs would likely act as effective strain sensors due to their high sensitivity to strain. However, further experimental research is needed to make a conclusive statement.