Title

Synthesis and characterization of crystalline transition metal dichalcogenides onto stretchable substrates by laser processing

Date of Award

2015

Degree Name

M.S. in Materials Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Andrey A. Voevodin

Abstract

Transistion metal dichalcogenides (TMDs) are an emerging class of materials for thin film transistors (TFTs). The inherent transparent properties, functionality and large lateral dimensions offer material selection for sensor technologies and transparent flexible displays. Low temperature processing of large crystallographic ordered films is needed to prevent thermal degradation of modern flexible electronic substrates. In this study, polycrystalline TMD growth mechanisms and, for the first time, a scalable processing technique used at room temperature will be demonstrated for application of semiconducting TMDs directly onto substrates by laser processing. A means of controlling the material structure by photon-phonon excitation provides a low temperature approach to controlling structural changes in materials; in particular, these studies are conducted on thin-film molybdenum disulfide and tungsten disulfide. A significant variance in both structure and electronic properties upon laser processing are observed in all samples. The direct deposition of molybdenum disulfide and tungsten disulfide on cross-linked polymers followed by localized laser annealing results in few atomic layer hexagonal sheets confirmed by Raman analysis, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The strong enhanced A1g and E2g bands in Raman and bonding characteristic in XPS suggests the layered S-Mo-S and S-W-S bonding. Conductive atomic force microscopy (C-AFM) on laser exposed samples showed a change in topography and electrical properties from insulating material to semiconducting after laser annealed. Laser annealing of amorphous films on polymer substrates is a simple and scalable approach to patterning complex patterns of semiconducting MoS2 film in an insulating matrix or generating large areas of semiconducting material for fabrication of 2D based flexible/stretchable electronics.

Keywords

Thin film transistors Design and construction, Chalcogenides, Transition metals, Laser fusion, Engineering, Materials Science, flexible electronics, nanomaterials, low temperature, transition metal dichalcogenides, thin film, heterostructures

Rights Statement

Copyright 2015, author

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