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Production and characterization of carbon-based nanomaterials: single- and double-layer graphene for high-pressure Raman spectroscopy
2010 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Graphene is a novel carbon nanomaterial and a great promise for nanotechnology applications in a near future, thanks to its outstanding mechanical and electronic properties. Less than 4 Angstroms (Å) in thickness, mono-crystal graphene flakes can reach tens of millimeters in their biggest dimension, making it a 2-dimensional crystal. This one-atom- thick sheet of pure sp² carbon displays Young modulus reaching 1TPa, a theoretical hardness higher than diamond, and is also a close-to-perfect (ballistic) conductor for heat and charge carriers. This dazzling array of exceptional properties makes graphene a state-of-the-art candidate for a list of applications in nanoscale electronic devices, bio-nanotechnologies, and advanced materials. Raman spectroscopy constitutes a non-destructive and time-efficient technique that probes many properties: the samples quality, thickness, doping. Most importantly, Resonance Raman Spectroscopy allows determination of the number of layers of graphene flakes (Single-Layer Graphene SLG, Double-Layer Graphene DLG, N-Layer Graphene NLG). A high-pressure study of graphene species by in-situ Resonance Raman Spectroscopy will provide a direct probing of the sp² carbon-carbon bond strength when SLG is studied, and the inter-planar interaction in the case of DLG. For an optimal comparative study, SLG and DLG graphene flakes need to be probed at High- Pressure without a supporting substrate. For this purpose, this thesis aims at the synthesis of high-quality graphene flakes in a reliable and reproducible manner. The second goal of the thesis is to extensively characterize these samples at ambient conditions, and to realize their transfer into a high-pressure device called Diamond Anvil-Cell (DAC) to prepare the in-situ experiments. Graphene samples are prepared using a mechanical exfoliation method, which was optimized to reach the fast and reproducible production of high-quality flakes, whose size can reach up to 20µm in their biggest dimension. Graphene samples provided by our collaborators are also investigated. The characterization confirms the production of high-quality supported samples (low or no D-band in the Raman spectra), and though transfer of the samples into the DAC is so far unsuccessful, a slight change in the materials used (from Cu-based grids to Au grids) should make the transfer possible and open the path to High-Pressure measurements for both types of samples. We have also proposed an innovative method to produce graphene from nano-lithographically patterned NanoPillars by mechanical exfoliation. Albeit unsuccessful as we first expected it, the cleavage, as showed by SEM, provokes a peeling of the pillars’ superior layers, accordingly to the expected mechanism. These efforts open the way to a new promising route for the synthesis of large area graphene-based nanostructures.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Nanomaterials, Graphene, Raman, Spectroscopy, High-Pressure
Keyword [sv]
URN: urn:nbn:se:ltu:diva-57964ISRN: LTU-PB-EX--10/024--SELocal ID: e91a985f-c1ff-4ee6-b0b5-7f0d42354ea6OAI: diva2:1031352
Subject / course
Student thesis, at least 30 credits
Educational program
Materials Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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