Analysis of the Chemical Vapor Deposition of Titanium Diboride: I . Equilibrium Thermodynamic Analysis

Abstract

A thermodynamic analysis of the chemical vapor deposition (CVD) of from gaseous , , and was performed using a general computer program for the calculation of heterogeneous equilibrium compositions. The conditions for the deposition of single phase and for the codeposition of plus boron were determined. Condensed and titanium metal phases were determined to be unstable when the above reactants are used. The gas composition in equilibrium with the deposited solid was computed as a function of the CVD parameters of deposition temperature, total pressure, and and fractions in the reactant gas. The gaseous species generally present in greatest abundance were , , , , , and . Theoretical deposition efficiencies were also calculated as a function of CVD parameters. The most efficient deposition was calculated to occur (i) at temperatures ii) under reduced pressures, and (iii) in the presence of an excess of hydrogen. Equilibrium calculations coupled with experimental results were also used to determine limits on the enthalpies of formation of and .