Epitaxial growth in the TiN/Si and TiN/GaAs metal-semiconductor systems with a large lattice mismatch was investigated. The orientation relationships have been found to be (OJ)l)TiN]] JOOl)Si for TiN growth on Si(OO1) and [OOl]TiN]] [llO]GaAs and [ 1 lO]TiN]] [ 1 lO]GaAs for TiN growth on GaAs ( 001) . The epitaxial growth is characterized by domain epitaxial orientation relationships with m lattice constants of epilayer matching with n of the substrate and with a small residual domain mismatch present in the epilayer. This residual mismatch is responsible for a coherent strain energy. The magnitude of compression of Ti-N bond in the first atomic layer, contributing to the chemical free energy during the initial stages of growth, is found to be a very important factor in determining the orientation relationship. This result was used to explain the differences in the orientation relationships between TiN/Si and TiN/GaAs systems. The various energy terms associated with the domain epitaxial growth are evaluated to illustrate that the domain epitaxial growth is energetically favorable compared to the lattice-mismatched epitaxial growth. The results of this analysis illustrate that the observed variations in the epitaxial growth are consistent with the 'minimum energy configurations associated with the domain epitaxial growth.

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Aluminum nitride thin films have been grown epitaxially on Si(111) substrates, for the first time, by pulsed laser ablation of sintered AlN target. The influence of process parameters such as laser energy density, substrate temperature, pulse repetition rate, nitrogen partial pressure, etc. on epitaxial growth has been investigated to obtain high quality AlN films. These films were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, x-ray diffraction (Θ and ω scans) technique, high resolution transmission electron microscopy, and scanning electron microscopy. The films deposited at laser energy density in the range of 2–3 J/cm2, substrate temperature of 750 °C, and base pressure of 3×10−7 Torr are single phase and highly oriented along c axis normal to the Si(111) planes. The results of x-ray diffraction and electron microscopy on these films clearly show the epitaxial growth of the AlN films with an orientational relationship of AlN[0001] ∥ Si[111] and AlN[21̄1̄0] ∥ Si[011̄]. The AlN/Si interface was found to be quite sharp without any indication of interfacial reaction. Laser physical vapor deposition is shown to produce high quality epitaxial AlN films with smooth surface morphology when deposited under optimized conditions.

ORAU for supporting this research effort. I would also like to thank Mr. Roberto Garcia and Ms. Laura Smith of AIF for training me initially in the use of SEM and helping me when I encountered problems. I also thank my friend and erstwhile group member Mr. Yoganand Saripalli for good discussions and support during the course of my research. I also thank Mr Kiran Sagi for the accommodation provided and making my stay at Oak Ridge-Knoxville a pleasurable and memorable one. I would like to thank all the staff of the Department of Materials Science and Engineering, especially Ms. Edna Deas for being so helpful during my entire MS program.

Aluminum nitride films have been deposited on Si͑111͒ substrates at different substrate temperatures using two techniques; pulsed laser deposition or reactive magnetron sputtering. The films deposited by either of the techniques have been characterized by x-ray diffraction and transmission electron microscopy to determine the crystalline quality, grain size, and epitaxial growth relation with respect to the substrate. The bonding characteristics and the residual stresses present in the films have been evaluated using Raman and Fourier transform infrared spectroscopy. Secondary ion mass spectrometry has been performed to determine the nitrogen stoichiometry and the presence of impurities such as oxygen and silicon. The adhesion strength of the AlN films to the silicon substrate and the wear resistance have been determined by scratch test and a specially designed microscopic wear test. A comparison of the different characteristic features associated with the AlN films deposited by pulsed laser deposition or magnetron sputtering is presented with particular emphasis to electronic and tribological applications.