Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Organometallic chemical vapour deposition (OMCVD) films usually have carbon as an impurity. This comes from the decomposition of the ligands in the organometallic precursor. Understanding the chemical reactions in the decomposition will greatly enhance our ability to control the impurity level in these films and also the epitaxial growth of the films. Depending on the pressure in the reactor, the important reactions could be in the gas phase or on the surface.;Decomposition of the precursor, cis-dimethyl platinum diisocyanide in presence of hydrogen shows reduction in carbon impurity. The decomposition was carried out in an infrared gas cell so that infrared light could be used in a transmission experiment as an in-situ probe of the reaction. It was found that the methyl platinum groups reacted with the hydrogen to give an increased yield of methane. The isocyanide ligand appears to leave the complex in one piece in an initial reversible equilibrium step. Subsequently they reacted with hydrogen gas to give ammonia. Kinetic measurements demonstrate a heterogenous component to the reaction.;Surface reactions were carried out in an ultra high vacuum (UHV) chamber. The main surface tools used in the study were Infrared Reflection Absorption Spectroscopy (IRRAS) and Temperature Programmed Desorption (TPD). The interaction of acetonitrile with methyl isocyanide with Pt(111) was also studied to assist in the overall understanding of the decomposition mechanism of cis-dimethyl platinum diisocyanide. When the precursor is adsorbed on a Pt(111) surface at 110 K, it does so dissociatively to give terminally bonded methyl isocyanide and some platinum hydrocarbon fragments. Thermochemistry of the complex on Pt(111) involved decomposition to H{dollar}\sb2{dollar} and HCN. The effect of surface carbon on Pt(111) appears to turn off the reactivity of the surface. When it was sufficiently turned off, monolayer adsorption was molecular. The thermal chemistry was also changed as dehydrogenation was greatly reduced. Loss of methyl isocyanide at 525 K was turned on instead and is consistent with decomposition studies at 580 K in the infrared cell where methyl isocyanide loss was also observed.



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