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Growth and characterization of Graphene

Graphene, a single sheet of Carbon atoms arranged in a honeycomb lattice, has become the most promising material for the future. Graphene has been studied for long time from a theoretical point of view. After its isolation in 2004 experiments began and its properties revealed.
Due to its electrical, optical and mechanical properties, this 2D material can be used in many applications ranging from electronics to medicine. Such applications include, but are not restricted to, energy storage, optoelectronics, THz electronics, transparent conductors, artificial leaves, materials reinforcement, drug delivery, cell scaffolds, and many others.
In order to be able to use Graphene for such applications it is necessary to have a fast, reliable and cost-effective production method.
During the past ten years many methods have been applied for the synthesis and isolation of Graphene. Among them the most promising are the so-called physical vapor and chemical vapor deposition methods.
In this work we will first introduce Graphene and its physical properties. Then we will concentrate on the Characterization techniques used to investigate this material; in particular we will see how Raman spectroscopy is a non-destructive invaluable tool for Graphene identification and characterization. Scanning electron microscopy is also a very useful tool for imaging of Graphene and it will be also described.
The third part of the work is dedicated to a survey of the Graphene growth and isolation methods. In particular our work will focus on Graphene growth by carbon precipitation on thin film metals and, thus, the aspects of thin film deposition and crystallization will be reviewed.
Last, we will present the results obtained in the Surfaces, Thin films & Nanostructures laboratory in L’Aquila on Graphene growth on Ni thin films. The technique used carbon precipitation and subsequent recrystallization in Graphene on top of Ni after thermal annealing, using as carbon sources both solid amorphous carbon (deposited by flash evaporation) and gaseous CH4 precursor.
The as-grown Graphene shows a characteristic Raman spectrum. The presence of D and D’ peaks reveal its defective structure while 2D peak fitting shows few-layer Graphene, compatible with the values found in literature.

Mostra/Nascondi contenuto.
1 G R A P H E N E Graphene is made of a single plane of carbon atoms arranged in an honeycomb two-dimensional (2D) lattice, and it is the building-block for the construction of the other graphitic materials with different dimensionality. It can be wrapped up into 0D fullerenes (but we need some pentagons to close a sphere of hexagons), rolled into 1D nan- otubes or stacked into 3D graphite (see figure 1.1). More than seventy years ago Landau and Peierls postulated the thermodynamical insta- bility of two-dimensional crystals, due to the divergent contribution of lattice vibrations. A three-dimensional base is necessary to let these structures be stable. This has been the path followed by Geim and Novoselov who, in2004, isolated and spotted Graphene upon a silicon oxide substrate (Novoselov et al. [1]). We will now discuss some of the properties of Graphene. 1.1 brief history The word “Graphene” has been used for the first time in1987 (Mouras et al. [2]) to describe a mono-atomic layer of graphite as one of the constituents of GICs (graphite intercalation compounds). Graphite is an abundant material on Earth and it is known as mineral since500 years. The word Graphene has been also used in the description of carbon nanotubes (CNT), of thin films of epitaxial graphite. Single graphite’s layers have been growth epitaxially upon differ- ent substrates since 1970 (Oshima and Nagashima [3]). “Epitaxial Graphene” is made of an hexagonal lattice one atom thick of sp 2 - hybridized carbon atoms, but the strong interaction between the sub- strate and the epitaxial Graphene hides the properties of Graphene. Attempts to exfoliate mechanically a single layer of graphite began in1990, but it wasn’t possible to find films thinner than50-100 layers until2004, when Geim and Novoselov from the Manchester Univer- sity succeeded in isolating one mono-atomic layer of graphite [1] on top of a silicon oxide substrate. The two researchers succeeded in doing so employing the so called “micro-mechanical cleavage” or, as better known, “tape method”. Silicon oxide insulates electrically the Graphene, weakly interacting with it, leaving its electrical properties unchanged. Theoretical studies on Graphene started in1947 by Philip R. Wallace in order to understand the electrical properties of graphite. 1

Tesi di Laurea Magistrale

Facoltà: Scienze Matematiche, Fisiche e Naturali

Autore: Adolfo De Sanctis Contatta »

Composta da 84 pagine.

 

Questa tesi ha raggiunto 266 click dal 15/01/2014.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.