Boundary effects in Van der Waals materials

Hammerland, Daniel

Undergraduate Honors Thesis

Boundary effects in Van der Waals materials Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/cn69m4705

Abstract

After the development of techniques for exfoliating [1, 2] and growing atomically thin crystals[3], transition metal dichalcogenides and graphene have both demonstrated having exceptional promise in applications of biosensing, spintronics, energy storage, and optoelectronics [4, 5, 6]. However, the electronic properties of these materials vary sensitively with crystal structure, orientation, number of layers, dopings and stacking order [7, 8, 9], making them highly sensitive to slight in- homogeneities. In order to optimally implement them for technological applications, we must first understand how these structural variations affect the material properties. Additionally, the small scale of these defects, on the order of a few nanometers, makes traditional spectroscopic analysis of these features difficult, impeding our ability to further our knowledge of them and ultimately limiting our ability to implement them in technology. In the last two decades, methods have been developed for overcoming these limitations [10]. Of these, Atomic Force Microscopy (AFM) and scattering-type Scanning Near-Field Optical Microscopy (s-SNOM) have been shown to be power- ful tools for observing light-matter interactions at sub-diffraction length scales and imaging with spatial resolution at the deep sub-wavelength scale [11]. In this thesis, I implement AFM, s-SNOM, and Raman spectroscopy in order to identify stacking layer grain boundaries in graphene as well as to study the nanoscale properties of two phases of MoTe₂ and to investigate an optically induced phase transition in MoTe₂.

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