Ariful Haque

Date of Graduation

Summer 2015

Degree

Master of Science in Materials Science

Department

Physics, Astronomy, and Materials Science

Committee Chair

Kartik Ghosh

Abstract

Large area uniform thin films of reduced graphene oxide (RGO) was synthesized by pulsed laser deposition (PLD) technique. A number of structural properties including the defect density, average size of sp2 clusters, and degree of reduction were investigated by Raman spectroscopy and X-ray diffraction (XRD) analysis. The temperature dependent (5K - 350K) four terminal electrical transport property measurement confirms variable range hopping and thermally activated transport mechanism of the charge carriers at low (5K - 210K) and high temperature (210K - 350K) regions, respectively. The calculated localization length, density of states (DOS) near Fermi level (EF), hopping energy, and Arrhenius energy gap provide significant information to explain excellent electrical properties in the RGO films. Hall mobility measurement confirms p-type characteristics of the thin films. The charge carrier Hall mobility can be engineered by tuning the growth parameters, and the measured maximum mobility was 1596 cm2V-1s-1 in the optimum sample. The optimization of the improved electrical property is well supported by Raman spectroscopy. The magneto resistance (MR) effect in the thin films provides sufficient information to reinforce the obtained electrical property information. The maximum values of measured positive MR are 27% and 12% at low (25K) and room (300K) temperatures, respectively. The transport properties of RGO samples are dependent on a number of factors including the density of the defect states, size of the sp2 clusters, degree of reduction, and the morphology of the thin film.

Keywords

graphene, graphene oxide, variable range hopping, raman spectroscopy, electrical transport property, magnetoresistance

Subject Categories

Materials Science and Engineering

Copyright

© Ariful Haque

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