No description available.

No description available.

No description available.

No description available.

The deposition of amorphous silicon from monosilane, disilane and mixtures of higher silanes has been studied. The literature available relating to the thermal decomposition of monosilane, disilane and trisilane has been reviewed and key thermodynamic data has been summarised. The presence of hydrogen in the as-deposited film has been confirmed and the dependence of the hydrogenation on the deposition parameters has been investigated. The bonding of hydrogen in the hydrogenated films has been investigated using FTIR spectroscopy. The films have been examined for their suitability as photovoltaic materials; dark conductivity, mobility band gap and the activation energy for the conduction process have been determined. The kinetics of the thermal decomposition of phosphine have been studied prior to the use of phosphine as a dopant for amorphous silicon. A brief study of the thermal decomposition of diborane was also carried out. Co-pyrolysis of silanes with phosphine and diborane to produce substitutionally doped material has been attempted, and the resultant material examined in the same way as the undoped material. The physical nature of the hydrogen incorporation is discussed and conclusions are drawn about the feasibility of controlling the hydrogen content of undoped and doped material.

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The hydropyrolysis of naphthalene was studied using two separate pieces of flow apparatus. One was operated at atmospheric pressure in the temperature range 1033 - 1173 K, on which the majority of the work was performed, and the other at high pressure, 70 atmospheres of hydrogen, and 1033 - 1073 K. A detailed description of the construction and operation of both pieces of apparatus is given. The following products were identified and quantitatively measured: dihydronaphthalene, indene, toluene, benzene, ethene, ethane, and methane. A number of polynuclear aromatic compounds were also identified but not quantified. The results revealed a complex situation involving back reaction, the involvement of the reactors surface, and the autocatalytic production of benzene and the gaseous products (ethene + ethane + methane). However, a relatively simple explanation was proffered. Its salient features are: (i) the initial formation of polynaphthalenes that may then condense to form liquid droplets - some of which are deposited on the reactor surface; (ii) the subsequent regeneration of naphthalene from these polymeric species, probably through reaction with H<SUP>.</SUP> radicals; (iii) the production of benzene and gaseous products by a radical branching mechanism. It is shown how this may involve polynaphthalene species with benzyne and acetylene acting as branching agents; (iv) the production of graphite-like compounds as a consequence of the liberation of benzene and gaseous products from polynaphthalenes; (v) the production of carbon clusters from liquid droplets of polymers.

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No description available.