Stability And Electronic Properties Of Single-walled GaN Nanotubes: The First-principles Investigations

GaN is a typical kind of wide band-gap III-V compounds semiconductors which have excellent optical, electrical and mechanical properties. Up to now, GaN bulk structures and GaN films have been studied extensively. However, the investigation of the one-dimensional GaN nano-materials is at the initial stage. As typical quasi-one-dimensional nano-materials, GaN nanotubes possess the unique mechanical, magnetic and optical properties. In this thesis, we investigate the stability and electronic properties of ultrathin GaN naontubes, as well as the magnetic properties of Mn-doped GaN nanotubes and the interaction between the Mn impurities using first-principles method which is based on density function theory (DFT). It mainly contains the following five chapters:In the first Chapter, we give a brief introduction for the research background, physical properties and potential applications of nanotube-structure systems, including carbon nanotubes and inorganic nanotubes. Moreover, the properties and structures of GaN bulk, as well as the theoretical and experimental studies of GaN nanotubes are introduced.Chapter 2 is devoted to the methods of calculation. We introduce the first-principles computation software VASP, which is based on the density function theory. The theoretical basis and computation function are concluded.Chapter 3, firstly, we investigate the electronic structures of GaN bulk and single-walled GaN nanotubes. Then, we pay our attention to the thermal stability of ultrathin GaN nanotubes and analysis the geometrical structure of these nanotubes which may be stable. Especially, the electronic properties of 3-5.5? GaN nanotubes are investigated.Chapter 4, through the calculations of Mn-doped GaN nanotubes, we study the magnetic properties of the doped systems and the interaction between the Mn impurities. Chapter 5, a conclusion is simply given. Based on the results that we have obtained, some deficiencies in our work are pointed out and a future investigation is also discussed.