Date of Graduation

Spring 2021

Degree

Master of Science in Materials Science

Department

Physics, Astronomy, and Materials Science

Committee Chair

Kartik Ghosh

Abstract

Carbon-based materials (CBMs) including graphene, carbon nanotubes (CNT), highly ordered pyrolytic graphite (HOPG), and pyrolytic carbon (PyC) have gained so much attention in research in recent years because of their unique electronic, optical, thermal, and mechanical properties. CBMs are relatively very stable and have minimal environmental footprint. Various techniques such as mechanical exfoliation, pulsed laser deposition, and chemical vapor deposition (CVD) have been used to grow CBMs and among them thermal CVD is the most common. This study aims to explore ways of reducing the energy requirement to produce CBMs, and for that, a novel pulsed laser-assisted CVD technique had been developed in our laboratory. The growth pattern was monitored by altering various growth parameters like gas flow rate, temperature, laser energy, and deposition time. CBMs were grown both on Si and Cu substrates, and better quality CBM films were found on Cu as it acts as a catalytic agent for two-dimensional growth. Raman spectroscopy confirms the presence of high quality PyC which was grown with optimum parameters (temperature of 750oC, CH4 gas flow rate of 20sccm, a laser frequency of 10Hz, energy density of 0.116J/cm2 per pulse). It is found that the local pulsed-laser bombardment helps in breaking the carbon-hydrogen bonds of CH4 at much lower temperature than its thermal decomposition temperature (1000oC-1200oC). With the further increase of temperature there was no significant change in the 2D peak intensity in Raman spectrum which is the indicator of the number of graphene layer. The intertwined graphene flakes of the PyC cause some surface roughness which is responsible for quenching the Raman 2D signal. Further development is needed to achieve a single layer of graphene and other 2D materials using the laser-assisted CVD technique.

Keywords

CVD, CBMs, PyC, Laser, Graphene, 2D materials, Laser-assisted CVD

Subject Categories

Materials Science and Engineering | Nanoscience and Nanotechnology | Semiconductor and Optical Materials

Copyright

© Abiodun Ademola Odusanya

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