Controllable Svnthesis And Growth Machanism Of Low Dimensional Ⅲ-Nitride Nanostructures

Why the growth of the crystals with various morphologies was obtained through the assembly of simialr atoms and/or molecules under the role of the same crystal structure? How do the intrinsic crystal structure and the exopathic condition work on the crystal growth process? How is the application of the materisals depended on the morphologies of the crystal? These three questions are crucial for the development and improvement of the materials science. Naturally, the development of nanoscience that is focusing on the materials phenomenon in the scale of atom, molecules and huge molecules need the resolution of these questions. In brief, the application of nanomaterials is enslaved to the shape and size of the crystal. Therefore, the core tasks for materials scientists to explore and research novel materials are the obtaining of controllable growth conditions of morphology and understanding the relationship between them. Group-Ⅲ nitrides AlN and InN are the main objects of study in this paper. The various AlN and InN low-dimensional nanostructures were synthesized under control of the experimental conditions, and the corresponding reasonable growth mechanisms were proposed based on the analysis of the relationship of growth condition, morphologies and size. The main reaserch works and conclusions are presented below:(1) The polymorphic hexagonal complex AlN nanostructures were synthesized by a simple chemical vapor deposition (CVD) approach. The as-prepared structures involve complex nanomaze, hexagonal nested arrays, hexagonal nanorod arrays and nanoparticle films. A relevant growth mechanism was suggested and interpreted with a focus on the nucleus arrangement combined with preferential growth. Observations of nucleus arrangement events certify the rationality of this mechanism. The ratio of AICl3/NH3is the key factor to control the growth, and which was assisted by the linear change of the growth temperature.(2) Au-assistant growth of InN nanowires were performed by the CVD system. The as-prepared nanowires exhibit two types of morphologies and growth directions coexistence:smooth nanowires (SNWs) and periodic nanowires (PNWs) growing along<1120> and<0001>, respectively. It was found that the SNWs with smaller diameter (～20nm) were obtained when smaller Au particles served as collector, while the PNWs with bigger diameter (-60nm) were grown when larger Au particles were presented. The main points of the growth mechanism include:a. Under the controlling of the size effect, the growth direction of the InN nanowires with larger diameter is dominanted by the lowest interfacial energy and the nanowires with small diameter is dominanted by the lowest surface energy; b. The melting degree of the alloy that related to the size effect, variational compositions of the droplet (the electronegativity) and VS-assistant VLS growth combined with different polarity of side crystal planes are crucial for modification of the PNW morphology.