Degree Type

Dissertation

Date of Award

2020

Degree Name

Master of Science

Department

Mechanical Engineering

Major

Mechanical Engineering

First Advisor

Xinwei Wang

Abstract

This work reports the interfacial thermal conductance (G) and radiative recombination efficiency (β) – also known as photoluminescence quantum yield (PL QY) – of monolayer WSe2 flakes supported by fused silica substrate via state-resolved energy transport Raman (ET-Raman). This is the first known work to consider the effect of radiative electron-hole recombination on the thermal transport characteristics of single layer transition metal dichalcogenides (TMDs). ET-Raman uses a continuous wave laser for steady state heating as well as nanosecond and picosecond lasers for transient energy transport to simultaneously heat the monolayer flakes and extract the Raman signal. The three lasers induce distinct heating phenomena that distinguish the interfacial thermal conductance and radiative recombination efficiency which can then be determined in tandem with 3D numerical modeling of the temperature rise from respective laser irradiation. For the five samples measured, G is found to range from 2.10 ± 0.14 to 15.9 ± 5.0 MW m-2 K-1 and β ranges from 36 ± 6 to 65 ± 7%. These values support the claim that interfacial phenomena such as surface roughness and 2D material-substrate bonding strength play critical roles in interfacial thermal transport and electron-hole recombination mechanisms in TMD monolayers. It is also determined that low-level defect density enhances the radiative recombination efficiency of single layer WSe2.

DOI

https://doi.org/10.31274/etd-20210114-66

Copyright Owner

Nick Hunter

Language

en

File Format

application/pdf

File Size

44 pages

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