Ab-initio studies of reactions to functionalize carbon nanotubes

Since the rediscovery of carbon nanotubes (CNTs) due to the publication of Sumio Iijima's article Helical microtubules of graphitic carbon in the magazine Nature in 1991 the interest in carbon nanotubes has rapidly increased. This bachelor thesis also deals with this popular material with the aim to functionalize CNTs for further uses in the microelectronic industry. A promising approach is the functionalization of the CNTs with metal nanoparticles or metal films. To achieve this, one can perform an atomic layer deposition (ALD) on CNTs. In the present work the Trimethylaluminum (TMA) ALD is the chosen process for the functionalization of the CNTs, which will be studied here. Since the available knowledge on the CNT-functionalization by gas phase reactions is very limited, a theoretical study of possible reaction pathways is necessary. Those studies are carried out with two modern quantumchemical programs, Turbomole and DMol³, which are described together with an introduction into Density Functional Theory, as well as an introduction of CNTs and the ALD process. A basic model of a CNT with a Single Vacancy defect, which had been selected according to the demands of the studies, is introduced. Because the TMA ALD process requires hydroxyl groups as its starting point, not only is the performance of a TMA ALD cycle on a CNT studied, but also reactions which result in the CNTs owning of hydroxyl groups. Consequently, this bachelor thesis will focus on two di erent aspects: The performance of one TMA ALD cycle and the study of possible educts for the TMA ALD process. This study of the educts includes possible structures which can be formed when a CNT comes into contact with air.:Abstract 1. Introduction 2. Carbon Nanotubes and the Atomic Layer Deposition 2.1. Carbon Nanotubes 2.1.1. Graphene and Its Relation to Carbon Nanotubes 2.1.2. Classi cations 2.1.3. Defects 2.2. Atomic Layer Deposition 2.2.1. Introduction to Atomic Layer Deposition 2.2.2. Trimethylaluminum Atomic Layer Deposition 3. Theoretical Background 3.1. The Schrödinger Equation and the Variational Principle 3.2. Electron Density 3.2.1. The Wave Function 3.2.2. The Electron Density 3.3. The Hohenberg-Kohn Theorems 3.3.1. The First Hohenberg-Kohn Theorem 3.3.2. The Second Hohenberg-Kohn Theorem 3.4. The Kohn-Sham Approach 4. Computational Details and the Model System 4.1. Model System 4.1.1. The Basic (5; 5)-CNT 4.1.2. Further Adjustments to the Basic (5; 5)-CNT 4.2. Computational Details 4.2.1. Materials Studio/Dmol³ 4.2.2. Turbomole 5. Results and Discussion 5.1. Educt Formation Reactions 5.1.1. Educts with Two Oxygen Atoms 5.1.2. Educts with Two Hydroxyl Groups and One Oxygen Atom 5.1.3. Educts with Two Hydroxyl Groups and Two Hydrogen Atoms 5.1.4. Educts with Four Hydroxyl Groups 5.1.5. Educts with Peroxy Groups 5.1.6. Summary - Educts 5.2. Performance of the First Trimethylaluminum Atomic Layer Deposition Cycle 5.2.1. The First Trimethylaluminum Atomic Layer Deposition Half Cycle 5.2.2. The Second Trimethylaluminum Atomic Layer Deposition Half Cycle 6. Summary and Outlook A. Appendix A.1. Note on the Multiplicity A.2. Note on the Computation Time A.3. Comparison between Dmol³ and Turbomole A.4. Tables of Energies for the Studied Educts in 5.1 A.5. Tables of Energies for the Study of the Trimethylaluminum Atomic Layer Deposition Cycle in 5.2 Bibliography Acknowledgmen