Molecular dynamics investigation of moire patterns in double-layer graphene

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye

Tezin Onay Tarihi: 2012

Öğrenci: GÖKÇE SÖKMEN

Danışman: HANDE TOFFOLİ

Özet:

Before Moire patterns are discovered in graphene, graphene was assumed to be found in only the rhombohedral form in nature. After transfer of graphene layer over another substrate was achieved by Andre Geim and Konstantin Novoselov, studies on graphene gained momentum. Following this, moire paterns were observed by scanning tunelling microscopy (STM) and high resolution transmision electron microscopy (HR-TEM). However, stability of these structures are still unknown. In this thesis, for the first time in literature, molecular dynamics of double layer graphene based Moire patterns are investigated as a result of the rotation of two graphene layers with LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) which has a GNU general public license. To model the two graphene layers, hexagonal graphene layers are generated by home writen Octave code. Then, periodicity condition for the Moire patterns are derived in chapter 2 according to rotation of graphene layers around their central axis, perpendicular to the layers. Then these layers with di fferent angles or temperature or size are simulated by LAMMPS. There are 4 kind of molecular dynamics simulations studied according to modeled flakes. These are grouped under the name of ’Experiment #’ according to the modeling structure. Experiment-1 simulates double layer hexagonal flakes of graphene at a temperature of 0.1K. Experiment-2 simulates periodic moire patterns under periodic boundary conditions and represents the infinitely large graphene layers at 10K. Experiment 3 is di erent version of the experiment 1 but at higher temperature (10K). Finally, experiment 4 is modeled to show the behaviour of the graphene flake on a growth or attached region. The atoms around the flakes are modeled as a rigid body and constructs some stress on the graphene flakes.