Honors Theses and Capstones

Date of Award

Spring 2020

Project Type

Senior Honors Thesis

College or School

CEPS

Department

Physics

Program or Major

Physics

Degree Name

Bachelor of Science

First Advisor

Shawna Hollen

Abstract

Scanning tunneling microscopy (STM) has transformed the field of condensed matter physics over the past few decades, allowing scientists to image materials at the atmomic scale, manipulate individual atoms, and probe electronic states on the surface of materials. In recent years, there have been numerous developments to introduce time-resolved measurements to STM in order to probe atomic-scale dynamic processes and combine spatial and temporal resolution. Advances like THz-STM setups achieve femtosecond resolution, but require complex external setups. All-electronic pump-probe spectroscopy for STM (directly analogous to optical pump-probe spectroscopy) has been pioneered by Loth et al., and newer applications (Natterer et al.) require only an arbitrary waveform generator to apply pump and probe pulses. In this thesis I describe a method of electronic pump-probe spectroscopy with STM to measure the time scale of mechanical deflections in graphene nanomembranes, and the results of a benchtop model experiment measuring the relaxation time of a red LED diode. I measured the upper bound of the relaxation time of the diode to be ~4 ns, and discuss the effect of electronic noise on the measurement. The method of pump-probe spectroscopy described in this thesis has the potential to revolutionize STM, as it provides a relatively low-cost method of introducing time-resolved measurements without requiring complex electronics or optical setups

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