Laser Processing of Diamond and Boron Nitride Epitaxial Layers

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This research supported by the National Science Foundation under the Materials Processing Joint Initiative. The objective of the research program is to study the epitaxial growth of thin film diamond and boron nitride using laser-induced photolytic and pyrolytic methods. The thin films are metastable at room temperature and atmospheric pressure, thereby requiring non- equilibrium methods to grow them. Pulsed laser irradiation introduces heating and transient atomic excitations locally to form the metastable phases. The materials will be grown epitaxially on magnesium oxide and silicon carbide on silicon substrates, where there are sets of major lattice planes which match those of the thin films. The diamond films will be doped during in-situ laser chemical vapor deposition by introducing dopant gases into the growth chamber. The emphasis in the research will be on the fundamental aspects of epitaxial growth, to include analysis of the formation of defects, and the effects of distribution of elastic strains and interfacial stresses. The thin films will be characterized using high-resolution and analytical transmission electron microscopy, Rutherford Backscattering Spectroscopy, Secondary Ion Mass Spectroscopy, Scanning Auger Electron Spectroscopy, Electron Spectroscopic Chemical Analysis, and Raman and infrared spectroscopy techniques will be used to characterize the chemical composition and the bonding characteristics. Some of the films will be evaluated for mechanical and electrical properties. Diamond and boron nitride are the hardest of all materials known to man, and are useful in applications such as cutting tools and wear resistant coatings. Other useful properties of diamond include high dielectric strength, chemical inertness, optical transparency, large band gap, high electrical resistivity, and high thermal conductivity. These properties make the material potentially useful for semiconductor devices for operation in high temperature and high radiation environments.