Studies on Growth of SiC and BN from Theory and Experiments

Sammanfattning: Smaller cellular telephones and more energy-efficient windows are just two examples of technological advances which call for new materials. Materials chemists seek to develop new materials, both out of pure curiosity to see which combination of elements and structures can be obtained and in efforts to produce materials, with specific properties. The starting materials (in solid, liquid or gaseous form) can then be combined and prepared in various ways. A chemical method that is gaining more attention for thin-film growth is Atomic Layer Deposition (ALD). This is a sophisticated type of vapor deposition in which the precursor gases are introduced separately into the reaction chamber.Silicon carbide (SiC) and cubic boron nitride (c-BN) are extremely hard diamond-like materials, both with a high potential for application within the modern microelectronics and tool industry. Hexagonal boron nitride (h-BN), with its graphite-like layered structure, is a promising ceramics material.Deposition of thin SiC and BN films from gaseous precursors has been studied by theoretical and experimental methods. The chemical composition and atomic arrangement of a growing surface is important for vapor growth. The surface may be terminated (e.g., by hydrogen atoms) and adopt various geometrical structures. Reconstruction of unterminated SiC(0001) surfaces, as well as H abstraction from the corresponding H-terminated surfaces, were studied using quantum mechanical calculations. Elementary reactions for vapor growth of SiC and BN, and in situ incorporation of dopant and contaminant species into these surfaces were also investigated theoretically. Moreover, thin films of BN were deposited by means of laser-assisted ALD. The general goal has been to predict and/or explain experimental results by investigating growth mechanisms.